[PATCH v2 3/6] arm64: irqflags: Use ICC sysregs to implement IRQ masking

From: Julien Thierry
Date: Wed Jan 17 2018 - 06:55:28 EST

From: Daniel Thompson <daniel.thompson@xxxxxxxxxx>

Currently irqflags is implemented using the PSR's I bit. It is possible
to implement irqflags by using the co-processor interface to the GIC.
Using the co-processor interface makes it feasible to simulate NMIs
using GIC interrupt prioritization.

This patch changes the irqflags macros to modify, save and restore
ICC_PMR_EL1. This has a substantial knock on effect for the rest of
the kernel. There are four reasons for this:

1. The state of the PMR becomes part of the interrupt context and must be
saved and restored during exceptions. It is saved on the stack as part
of the saved context when an interrupt/exception is taken.

2. The hardware automatically masks the I bit (at boot, during traps, etc).
I bit status is inherited in the different kernel entry types and PMR
value is unaffected by exception. So once the I bit is inherited, IRQ
flags are back to the same state as before the exception.
In the interrupt entry, however, daif flags are not inherited.
Switching from I bit masking to PMR masking is done after acknowledging
the interrupt (otherwise PMR would prevent the IRQ ack).

3. Some instructions, such as wfi, require that the PMR not be used
for interrupt masking. Before calling these instructions we must
switch from PMR masking to I bit masking.
This is also the case when KVM runs a guest, if the CPU receives
an interrupt from the host, interrupts must not be masked in PMR
otherwise the GIC will not signal it to the CPU.

4. We use the alternatives system to allow a single kernel to boot and
be switched to the alternative masking approach at runtime.

Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
[julien.thierry@xxxxxxx: changes reflected in commit,
message, fixes, renaming]
Signed-off-by: Julien Thierry <julien.thierry@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jason Cooper <jason@xxxxxxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
---
arch/arm64/Kconfig | 15 ++++
arch/arm64/include/asm/arch_gicv3.h | 37 ++++++++++
arch/arm64/include/asm/assembler.h | 23 +++++-
arch/arm64/include/asm/daifflags.h | 36 +++++++---
arch/arm64/include/asm/efi.h | 5 ++
arch/arm64/include/asm/irqflags.h | 125 +++++++++++++++++++++++++++++++++
arch/arm64/include/asm/processor.h | 4 ++
arch/arm64/include/asm/ptrace.h | 14 +++-
arch/arm64/kernel/asm-offsets.c | 1 +
arch/arm64/kernel/entry.S | 28 +++++++-
arch/arm64/kernel/head.S | 38 ++++++++++
arch/arm64/kernel/process.c | 6 ++
arch/arm64/kernel/smp.c | 8 +++
arch/arm64/kvm/hyp/hyp-entry.S | 20 ++++++
arch/arm64/kvm/hyp/switch.c | 21 ++++++
arch/arm64/mm/proc.S | 23 ++++++
drivers/irqchip/irq-gic-v3-its.c | 2 +-
drivers/irqchip/irq-gic-v3.c | 82 +++++++++++----------
include/linux/irqchip/arm-gic-common.h | 6 ++
include/linux/irqchip/arm-gic.h | 5 --
20 files changed, 439 insertions(+), 60 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c9a7e9e..9834ff4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -850,6 +850,21 @@ config FORCE_MAX_ZONEORDER
However for 4K, we choose a higher default value, 11 as opposed to 10, giving us
4M allocations matching the default size used by generic code.

+config USE_ICC_SYSREGS_FOR_IRQFLAGS
+ bool "Use ICC system registers for IRQ masking"
+ select CONFIG_ARM_GIC_V3
+ help
+ Using the ICC system registers for IRQ masking makes it possible
+ to simulate NMI on ARM64 systems. This allows several interesting
+ features (especially debug features) to be used on these systems.
+
+ Say Y here to implement IRQ masking using ICC system
+ registers when the GIC System Registers are available. The changes
+ are applied dynamically using the alternatives system so it is safe
+ to enable this option on systems with older interrupt controllers.
+
+ If unsure, say N
+
menuconfig ARMV8_DEPRECATED
bool "Emulate deprecated/obsolete ARMv8 instructions"
depends on COMPAT
diff --git a/arch/arm64/include/asm/arch_gicv3.h b/arch/arm64/include/asm/arch_gicv3.h
index 9becba9..490bb3a 100644
--- a/arch/arm64/include/asm/arch_gicv3.h
+++ b/arch/arm64/include/asm/arch_gicv3.h
@@ -76,6 +76,11 @@ static inline u64 gic_read_iar_cavium_thunderx(void)
return irqstat;
}

+static inline u32 gic_read_pmr(void)
+{
+ return read_sysreg_s(SYS_ICC_PMR_EL1);
+}
+
static inline void gic_write_pmr(u32 val)
{
write_sysreg_s(val, SYS_ICC_PMR_EL1);
@@ -145,5 +150,37 @@ static inline void gic_write_bpr1(u32 val)
#define gits_write_vpendbaser(v, c) writeq_relaxed(v, c)
#define gits_read_vpendbaser(c) readq_relaxed(c)

+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+static inline void gic_start_pmr_masking(void)
+{
+ if (cpus_have_const_cap(ARM64_HAS_SYSREG_GIC_CPUIF)) {
+ gic_write_pmr(ICC_PMR_EL1_MASKED);
+ asm volatile ("msr daifclr, #2" : : : "memory");
+ }
+}
+
+static inline u32 gic_pmr_save_and_unmask(void)
+{
+ if (cpus_have_const_cap(ARM64_HAS_SYSREG_GIC_CPUIF)) {
+ u32 old;
+
+ old = gic_read_pmr();
+ gic_write_pmr(ICC_PMR_EL1_UNMASKED);
+ dsb(sy);
+
+ return old;
+ } else {
+ /* Idle priority, no masking */
+ return ICC_PMR_EL1_UNMASKED;
+ }
+}
+
+static inline void gic_pmr_restore(u32 pmr)
+{
+ if (cpus_have_const_cap(ARM64_HAS_SYSREG_GIC_CPUIF))
+ gic_write_pmr(pmr);
+}
+#endif
+
#endif /* __ASSEMBLY__ */
#endif /* __ASM_ARCH_GICV3_H */
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 8b16828..d320bd6 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -23,6 +23,7 @@
#ifndef __ASM_ASSEMBLER_H
#define __ASM_ASSEMBLER_H

+#include <asm/alternative.h>
#include <asm/asm-offsets.h>
#include <asm/cpufeature.h>
#include <asm/debug-monitors.h>
@@ -63,12 +64,30 @@
/*
* Enable and disable interrupts.
*/
- .macro disable_irq
+ .macro disable_irq, tmp
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ mov \tmp, #ICC_PMR_EL1_MASKED
+alternative_if_not ARM64_HAS_SYSREG_GIC_CPUIF
msr daifset, #2
+alternative_else
+ msr_s SYS_ICC_PMR_EL1, \tmp
+alternative_endif
+#else
+ msr daifset, #2
+#endif
.endm

- .macro enable_irq
+ .macro enable_irq, tmp
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ mov \tmp, #ICC_PMR_EL1_UNMASKED
+alternative_if_not ARM64_HAS_SYSREG_GIC_CPUIF
msr daifclr, #2
+alternative_else
+ msr_s SYS_ICC_PMR_EL1, \tmp
+alternative_endif
+#else
+ msr daifclr, #2
+#endif
.endm

.macro save_and_disable_irq, flags
diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h
index 22e4c83..ba85822 100644
--- a/arch/arm64/include/asm/daifflags.h
+++ b/arch/arm64/include/asm/daifflags.h
@@ -18,9 +18,24 @@

#include <linux/irqflags.h>

+#ifndef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+
#define DAIF_PROCCTX 0
#define DAIF_PROCCTX_NOIRQ PSR_I_BIT

+#else
+
+#define DAIF_PROCCTX \
+ (cpus_have_const_cap(ARM64_HAS_SYSREG_GIC_CPUIF) ? \
+ MAKE_ARCH_FLAGS(0, ICC_PMR_EL1_UNMASKED) : \
+ 0)
+
+#define DAIF_PROCCTX_NOIRQ \
+ (cpus_have_const_cap(ARM64_HAS_SYSREG_GIC_CPUIF) ? \
+ MAKE_ARCH_FLAGS(0, ICC_PMR_EL1_MASKED) : \
+ PSR_I_BIT)
+#endif
+
/* mask/save/unmask/restore all exceptions, including interrupts. */
static inline void local_daif_mask(void)
{
@@ -36,11 +51,8 @@ static inline unsigned long local_daif_save(void)
{
unsigned long flags;

- asm volatile(
- "mrs %0, daif // local_daif_save\n"
- : "=r" (flags)
- :
- : "memory");
+ flags = arch_local_save_flags();
+
local_daif_mask();

return flags;
@@ -54,17 +66,21 @@ static inline void local_daif_unmask(void)
:
:
: "memory");
+
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ /* Unmask IRQs in PMR if needed */
+ if (cpus_have_const_cap(ARM64_HAS_SYSREG_GIC_CPUIF))
+ arch_local_irq_enable();
+#endif
}

static inline void local_daif_restore(unsigned long flags)
{
if (!arch_irqs_disabled_flags(flags))
trace_hardirqs_on();
- asm volatile(
- "msr daif, %0 // local_daif_restore"
- :
- : "r" (flags)
- : "memory");
+
+ arch_local_irq_restore(flags);
+
if (arch_irqs_disabled_flags(flags))
trace_hardirqs_off();
}
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index c4cd508..421525f 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -40,7 +40,12 @@
efi_virtmap_unload(); \
})

+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+#define ARCH_EFI_IRQ_FLAGS_MASK \
+ (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT | ARCH_FLAG_PMR_EN)
+#else
#define ARCH_EFI_IRQ_FLAGS_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
+#endif

/* arch specific definitions used by the stub code */

diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
index 24692ed..3d5d443 100644
--- a/arch/arm64/include/asm/irqflags.h
+++ b/arch/arm64/include/asm/irqflags.h
@@ -18,7 +18,10 @@

#ifdef __KERNEL__

+#include <asm/alternative.h>
+#include <asm/cpufeature.h>
#include <asm/ptrace.h>
+#include <asm/sysreg.h>

/*
* Aarch64 has flags for masking: Debug, Asynchronous (serror), Interrupts and
@@ -33,6 +36,7 @@
* unmask it at all other times.
*/

+#ifndef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
/*
* CPU interrupt mask handling.
*/
@@ -96,5 +100,126 @@ static inline int arch_irqs_disabled_flags(unsigned long flags)
{
return flags & PSR_I_BIT;
}
+
+static inline void maybe_switch_to_sysreg_gic_cpuif(void) {}
+
+#else /* CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS */
+
+#define ARCH_FLAG_PMR_EN 0x1
+
+#define MAKE_ARCH_FLAGS(daif, pmr) \
+ ((daif) | (((pmr) >> ICC_PMR_EL1_EN_SHIFT) & ARCH_FLAG_PMR_EN))
+
+#define ARCH_FLAGS_GET_PMR(flags) \
+ ((((flags) & ARCH_FLAG_PMR_EN) << ICC_PMR_EL1_EN_SHIFT) \
+ | ICC_PMR_EL1_MASKED)
+
+#define ARCH_FLAGS_GET_DAIF(flags) ((flags) & ~ARCH_FLAG_PMR_EN)
+
+/*
+ * CPU interrupt mask handling.
+ */
+static inline unsigned long arch_local_irq_save(void)
+{
+ unsigned long flags, masked = ICC_PMR_EL1_MASKED;
+ unsigned long pmr = 0;
+
+ asm volatile(ALTERNATIVE(
+ "mrs %0, daif // arch_local_irq_save\n"
+ "msr daifset, #2\n"
+ "mov %1, #" __stringify(ICC_PMR_EL1_UNMASKED),
+ /* --- */
+ "mrs %0, daif\n"
+ "mrs_s %1, " __stringify(SYS_ICC_PMR_EL1) "\n"
+ "msr_s " __stringify(SYS_ICC_PMR_EL1) ", %2",
+ ARM64_HAS_SYSREG_GIC_CPUIF)
+ : "=&r" (flags), "=&r" (pmr)
+ : "r" (masked)
+ : "memory");
+
+ return MAKE_ARCH_FLAGS(flags, pmr);
+}
+
+static inline void arch_local_irq_enable(void)
+{
+ unsigned long unmasked = ICC_PMR_EL1_UNMASKED;
+
+ asm volatile(ALTERNATIVE(
+ "msr daifclr, #2 // arch_local_irq_enable\n"
+ "nop",
+ "msr_s " __stringify(SYS_ICC_PMR_EL1) ",%0\n"
+ "dsb sy",
+ ARM64_HAS_SYSREG_GIC_CPUIF)
+ :
+ : "r" (unmasked)
+ : "memory");
+}
+
+static inline void arch_local_irq_disable(void)
+{
+ unsigned long masked = ICC_PMR_EL1_MASKED;
+
+ asm volatile(ALTERNATIVE(
+ "msr daifset, #2 // arch_local_irq_disable",
+ "msr_s " __stringify(SYS_ICC_PMR_EL1) ",%0",
+ ARM64_HAS_SYSREG_GIC_CPUIF)
+ :
+ : "r" (masked)
+ : "memory");
+}
+
+/*
+ * Save the current interrupt enable state.
+ */
+static inline unsigned long arch_local_save_flags(void)
+{
+ unsigned long flags;
+ unsigned long pmr = 0;
+
+ asm volatile(ALTERNATIVE(
+ "mrs %0, daif // arch_local_save_flags\n"
+ "mov %1, #" __stringify(ICC_PMR_EL1_UNMASKED),
+ "mrs %0, daif\n"
+ "mrs_s %1, " __stringify(SYS_ICC_PMR_EL1),
+ ARM64_HAS_SYSREG_GIC_CPUIF)
+ : "=r" (flags), "=r" (pmr)
+ :
+ : "memory");
+
+ return MAKE_ARCH_FLAGS(flags, pmr);
+}
+
+/*
+ * restore saved IRQ state
+ */
+static inline void arch_local_irq_restore(unsigned long flags)
+{
+ unsigned long pmr = ARCH_FLAGS_GET_PMR(flags);
+
+ flags = ARCH_FLAGS_GET_DAIF(flags);
+
+ asm volatile(ALTERNATIVE(
+ "msr daif, %0 // arch_local_irq_restore\n"
+ "nop\n"
+ "nop",
+ "msr daif, %0\n"
+ "msr_s " __stringify(SYS_ICC_PMR_EL1) ",%1\n"
+ "dsb sy",
+ ARM64_HAS_SYSREG_GIC_CPUIF)
+ :
+ : "r" (flags), "r" (pmr)
+ : "memory");
+}
+
+static inline int arch_irqs_disabled_flags(unsigned long flags)
+{
+ return (ARCH_FLAGS_GET_DAIF(flags) & (PSR_I_BIT)) |
+ !(ARCH_FLAGS_GET_PMR(flags) & ICC_PMR_EL1_EN_BIT);
+}
+
+void maybe_switch_to_sysreg_gic_cpuif(void);
+
+#endif /* CONFIG_IRQFLAGS_GIC_MASKING */
+
#endif
#endif
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 023cacb..d569dee 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -137,6 +137,10 @@ static inline void start_thread_common(struct pt_regs *regs, unsigned long pc)
memset(regs, 0, sizeof(*regs));
forget_syscall(regs);
regs->pc = pc;
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ /* Have IRQs enabled by default */
+ regs->pmr_save = ICC_PMR_EL1_UNMASKED;
+#endif
}

static inline void start_thread(struct pt_regs *regs, unsigned long pc,
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index 6069d66..aa1e948 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h
@@ -25,6 +25,12 @@
#define CurrentEL_EL1 (1 << 2)
#define CurrentEL_EL2 (2 << 2)

+/* PMR values used to mask/unmask interrupts */
+#define ICC_PMR_EL1_EN_SHIFT 6
+#define ICC_PMR_EL1_EN_BIT (1 << ICC_PMR_EL1_EN_SHIFT) // PMR IRQ enable
+#define ICC_PMR_EL1_UNMASKED 0xf0
+#define ICC_PMR_EL1_MASKED (ICC_PMR_EL1_UNMASKED ^ ICC_PMR_EL1_EN_BIT)
+
/* AArch32-specific ptrace requests */
#define COMPAT_PTRACE_GETREGS 12
#define COMPAT_PTRACE_SETREGS 13
@@ -136,7 +142,7 @@ struct pt_regs {
#endif

u64 orig_addr_limit;
- u64 unused; // maintain 16 byte alignment
+ u64 pmr_save;
u64 stackframe[2];
};

@@ -171,8 +177,14 @@ static inline void forget_syscall(struct pt_regs *regs)
#define processor_mode(regs) \
((regs)->pstate & PSR_MODE_MASK)

+#ifndef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
#define interrupts_enabled(regs) \
(!((regs)->pstate & PSR_I_BIT))
+#else
+#define interrupts_enabled(regs) \
+ ((!((regs)->pstate & PSR_I_BIT)) && \
+ ((regs)->pmr_save & ICC_PMR_EL1_EN_BIT))
+#endif

#define fast_interrupts_enabled(regs) \
(!((regs)->pstate & PSR_F_BIT))
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 71bf088..6b00b0d 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -75,6 +75,7 @@ int main(void)
DEFINE(S_ORIG_X0, offsetof(struct pt_regs, orig_x0));
DEFINE(S_SYSCALLNO, offsetof(struct pt_regs, syscallno));
DEFINE(S_ORIG_ADDR_LIMIT, offsetof(struct pt_regs, orig_addr_limit));
+ DEFINE(S_PMR_SAVE, offsetof(struct pt_regs, pmr_save));
DEFINE(S_STACKFRAME, offsetof(struct pt_regs, stackframe));
DEFINE(S_FRAME_SIZE, sizeof(struct pt_regs));
BLANK();
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 6d14b8f..8209b45 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -20,6 +20,7 @@

#include <linux/init.h>
#include <linux/linkage.h>
+#include <linux/irqchip/arm-gic-v3.h>

#include <asm/alternative.h>
#include <asm/assembler.h>
@@ -210,6 +211,16 @@ alternative_else_nop_endif
msr sp_el0, tsk
.endif

+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ /* Save pmr */
+alternative_if ARM64_HAS_SYSREG_GIC_CPUIF
+ mrs_s x20, SYS_ICC_PMR_EL1
+alternative_else
+ mov x20, #ICC_PMR_EL1_UNMASKED
+alternative_endif
+ str x20, [sp, #S_PMR_SAVE]
+#endif
+
/*
* Registers that may be useful after this macro is invoked:
*
@@ -230,6 +241,15 @@ alternative_else_nop_endif
/* No need to restore UAO, it will be restored from SPSR_EL1 */
.endif

+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ /* Restore pmr, ensuring IRQs are off before restoring context. */
+alternative_if ARM64_HAS_SYSREG_GIC_CPUIF
+ ldr x20, [sp, #S_PMR_SAVE]
+ msr_s SYS_ICC_PMR_EL1, x20
+ dsb sy
+alternative_else_nop_endif
+#endif
+
ldp x21, x22, [sp, #S_PC] // load ELR, SPSR
.if \el == 0
ct_user_enter
@@ -820,17 +840,18 @@ ENDPROC(el0_error)
* and this includes saving x0 back into the kernel stack.
*/
ret_fast_syscall:
- disable_daif
+ disable_irq x21 // disable interrupts
str x0, [sp, #S_X0] // returned x0
ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for syscall tracing
and x2, x1, #_TIF_SYSCALL_WORK
cbnz x2, ret_fast_syscall_trace
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
+ disable_daif
enable_step_tsk x1, x2
kernel_exit 0
ret_fast_syscall_trace:
- enable_daif
+ enable_daif // enable interrupts
b __sys_trace_return_skipped // we already saved x0

/*
@@ -848,11 +869,12 @@ work_pending:
* "slow" syscall return path.
*/
ret_to_user:
- disable_daif
+ disable_irq x21 // disable interrupts
ldr x1, [tsk, #TSK_TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
finish_ret_to_user:
+ disable_daif
enable_step_tsk x1, x2
kernel_exit 0
ENDPROC(ret_to_user)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index e3cb9fb..ec2eb4a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -563,6 +563,44 @@ set_cpu_boot_mode_flag:
ret
ENDPROC(set_cpu_boot_mode_flag)

+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+/*
+ * void maybe_switch_to_sysreg_gic_cpuif(void)
+ *
+ * Enable interrupt controller system register access if this feature
+ * has been detected by the alternatives system.
+ *
+ * Before we jump into generic code we must enable interrupt controller system
+ * register access because this is required by the irqflags macros. We must
+ * also mask interrupts at the PMR and unmask them within the PSR. That leaves
+ * us set up and ready for the kernel to make its first call to
+ * arch_local_irq_enable().
+
+ *
+ */
+ENTRY(maybe_switch_to_sysreg_gic_cpuif)
+alternative_if_not ARM64_HAS_SYSREG_GIC_CPUIF
+ b 1f
+alternative_else
+ mrs_s x0, SYS_ICC_SRE_EL1
+alternative_endif
+ orr x0, x0, #1
+ msr_s SYS_ICC_SRE_EL1, x0 // Set ICC_SRE_EL1.SRE==1
+ isb // Make sure SRE is now set
+ mrs x0, daif
+ tbz x0, #7, no_mask_pmr // Are interrupts on?
+ mov x0, ICC_PMR_EL1_MASKED
+ msr_s SYS_ICC_PMR_EL1, x0 // Prepare for unmask of I bit
+ msr daifclr, #2 // Clear the I bit
+ b 1f
+no_mask_pmr:
+ mov x0, ICC_PMR_EL1_UNMASKED
+ msr_s SYS_ICC_PMR_EL1, x0
+1:
+ ret
+ENDPROC(maybe_switch_to_sysreg_gic_cpuif)
+#endif
+
/*
* These values are written with the MMU off, but read with the MMU on.
* Writers will invalidate the corresponding address, discarding up to a
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 6b7dcf4..56871f2 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -66,6 +66,8 @@
EXPORT_SYMBOL(__stack_chk_guard);
#endif

+#include <asm/arch_gicv3.h>
+
/*
* Function pointers to optional machine specific functions
*/
@@ -224,6 +226,7 @@ void __show_regs(struct pt_regs *regs)
print_symbol("pc : %s\n", regs->pc);
print_symbol("lr : %s\n", lr);
printk("sp : %016llx\n", sp);
+ printk("pmr_save: %08llx\n", regs->pmr_save);

i = top_reg;

@@ -349,6 +352,9 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
} else {
memset(childregs, 0, sizeof(struct pt_regs));
childregs->pstate = PSR_MODE_EL1h;
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ childregs->pmr_save = ICC_PMR_EL1_UNMASKED;
+#endif
if (IS_ENABLED(CONFIG_ARM64_UAO) &&
cpus_have_const_cap(ARM64_HAS_UAO))
childregs->pstate |= PSR_UAO_BIT;
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 37361b5..ec56ee1 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -221,6 +221,8 @@ asmlinkage void secondary_start_kernel(void)
struct mm_struct *mm = &init_mm;
unsigned int cpu;

+ maybe_switch_to_sysreg_gic_cpuif();
+
cpu = task_cpu(current);
set_my_cpu_offset(per_cpu_offset(cpu));

@@ -459,6 +461,12 @@ void __init smp_prepare_boot_cpu(void)
* and/or scheduling is enabled.
*/
apply_alternatives_early();
+
+ /*
+ * Conditionally switch to GIC PMR for interrupt masking (this
+ * will be a nop if we are using normal interrupt masking)
+ */
+ maybe_switch_to_sysreg_gic_cpuif();
}

static u64 __init of_get_cpu_mpidr(struct device_node *dn)
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 5170ce1..e5e97e8 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -42,7 +42,27 @@
.endm

ENTRY(__vhe_hyp_call)
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+alternative_if ARM64_HAS_SYSREG_GIC_CPUIF
+ /*
+ * In non-VHE, trapping to EL2 will set the PSR.I bit.
+ * Force it here whenever we are playing with PMR.
+ */
+ str x19, [sp, #-16]!
+ mrs x19, daif
+ msr daifset, #2
+alternative_else_nop_endif
+#endif
+
do_el2_call
+
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+alternative_if ARM64_HAS_SYSREG_GIC_CPUIF
+ msr daif, x19
+ ldr x19, [sp], #16
+alternative_else_nop_endif
+#endif
+
/*
* We used to rely on having an exception return to get
* an implicit isb. In the E2H case, we don't have it anymore.
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index f7c651f..4fac70d 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -18,6 +18,9 @@
#include <linux/types.h>
#include <linux/jump_label.h>

+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+#include <asm/arch_gicv3.h>
+#endif
#include <asm/kvm_asm.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_hyp.h>
@@ -303,6 +306,19 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
struct kvm_cpu_context *guest_ctxt;
bool fp_enabled;
u64 exit_code;
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ u32 pmr_save;
+#endif
+
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ /*
+ * Having IRQs masked via PMR when entering the guest means the GIC
+ * will not signal the CPU of interrupts of lower priority, and the
+ * only way to get out will be via guest exceptions.
+ * Naturally, we want to avoid this.
+ */
+ pmr_save = gic_pmr_save_and_unmask();
+#endif

vcpu = kern_hyp_va(vcpu);
write_sysreg(vcpu, tpidr_el2);
@@ -417,6 +433,11 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
*/
__debug_cond_restore_host_state(vcpu);

+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ /* PMR was unmasked, no need for dsb */
+ gic_pmr_restore(pmr_save);
+#endif
+
return exit_code;
}

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 95233df..8b91661 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -20,6 +20,7 @@

#include <linux/init.h>
#include <linux/linkage.h>
+#include <linux/irqchip/arm-gic-v3.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/hwcap.h>
@@ -47,11 +48,33 @@
* cpu_do_idle()
*
* Idle the processor (wait for interrupt).
+ *
+ * If CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS is set we must do additional
+ * work to ensure that interrupts are not masked at the PMR (because the
+ * core will not wake up if we block the wake up signal in the interrupt
+ * controller).
*/
ENTRY(cpu_do_idle)
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+alternative_if_not ARM64_HAS_SYSREG_GIC_CPUIF
+#endif
+ dsb sy // WFI may enter a low-power mode
+ wfi
+ ret
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+alternative_else
+ mrs x0, daif // save I bit
+ msr daifset, #2 // set I bit
+ mrs_s x1, SYS_ICC_PMR_EL1 // save PMR
+alternative_endif
+ mov x2, #ICC_PMR_EL1_UNMASKED
+ msr_s SYS_ICC_PMR_EL1, x2 // unmask at PMR
dsb sy // WFI may enter a low-power mode
wfi
+ msr_s SYS_ICC_PMR_EL1, x1 // restore PMR
+ msr daif, x0 // restore I bit
ret
+#endif
ENDPROC(cpu_do_idle)

#ifdef CONFIG_CPU_PM
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 06f025f..35e5f45 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -60,7 +60,7 @@
#define LPI_PROPBASE_SZ ALIGN(BIT(LPI_NRBITS), SZ_64K)
#define LPI_PENDBASE_SZ ALIGN(BIT(LPI_NRBITS) / 8, SZ_64K)

-#define LPI_PROP_DEFAULT_PRIO 0xa0
+#define LPI_PROP_DEFAULT_PRIO GICD_INT_DEF_PRI

/*
* Collection structure - just an ID, and a redistributor address to
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index b56c3e2..df51d96 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -71,9 +71,6 @@ struct gic_chip_data {
#define gic_data_rdist_rd_base() (gic_data_rdist()->rd_base)
#define gic_data_rdist_sgi_base() (gic_data_rdist_rd_base() + SZ_64K)

-/* Our default, arbitrary priority value. Linux only uses one anyway. */
-#define DEFAULT_PMR_VALUE 0xf0
-
static inline unsigned int gic_irq(struct irq_data *d)
{
return d->hwirq;
@@ -348,48 +345,55 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
{
u32 irqnr;

- do {
- irqnr = gic_read_iar();
+ irqnr = gic_read_iar();

- if (likely(irqnr > 15 && irqnr < 1020) || irqnr >= 8192) {
- int err;
+#ifdef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ isb();
+ /* Masking IRQs earlier would prevent to ack the current interrupt */
+ gic_start_pmr_masking();
+#endif

- if (static_key_true(&supports_deactivate))
+ if (likely(irqnr > 15 && irqnr < 1020) || irqnr >= 8192) {
+ int err;
+
+ if (static_key_true(&supports_deactivate))
+ gic_write_eoir(irqnr);
+ else {
+#ifndef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
+ isb();
+#endif
+ }
+
+ err = handle_domain_irq(gic_data.domain, irqnr, regs);
+ if (err) {
+ WARN_ONCE(true, "Unexpected interrupt received!\n");
+ if (static_key_true(&supports_deactivate)) {
+ if (irqnr < 8192)
+ gic_write_dir(irqnr);
+ } else {
gic_write_eoir(irqnr);
- else
- isb();
-
- err = handle_domain_irq(gic_data.domain, irqnr, regs);
- if (err) {
- WARN_ONCE(true, "Unexpected interrupt received!\n");
- if (static_key_true(&supports_deactivate)) {
- if (irqnr < 8192)
- gic_write_dir(irqnr);
- } else {
- gic_write_eoir(irqnr);
- }
}
- continue;
}
- if (irqnr < 16) {
- gic_write_eoir(irqnr);
- if (static_key_true(&supports_deactivate))
- gic_write_dir(irqnr);
+ return;
+ }
+ if (irqnr < 16) {
+ gic_write_eoir(irqnr);
+ if (static_key_true(&supports_deactivate))
+ gic_write_dir(irqnr);
#ifdef CONFIG_SMP
- /*
- * Unlike GICv2, we don't need an smp_rmb() here.
- * The control dependency from gic_read_iar to
- * the ISB in gic_write_eoir is enough to ensure
- * that any shared data read by handle_IPI will
- * be read after the ACK.
- */
- handle_IPI(irqnr, regs);
+ /*
+ * Unlike GICv2, we don't need an smp_rmb() here.
+ * The control dependency from gic_read_iar to
+ * the ISB in gic_write_eoir is enough to ensure
+ * that any shared data read by handle_IPI will
+ * be read after the ACK.
+ */
+ handle_IPI(irqnr, regs);
#else
- WARN_ONCE(true, "Unexpected SGI received!\n");
+ WARN_ONCE(true, "Unexpected SGI received!\n");
#endif
- continue;
- }
- } while (irqnr != ICC_IAR1_EL1_SPURIOUS);
+ return;
+ }
}

static void __init gic_dist_init(void)
@@ -543,8 +547,10 @@ static void gic_cpu_sys_reg_init(void)
if (!gic_enable_sre())
pr_err("GIC: unable to set SRE (disabled at EL2), panic ahead\n");

+#ifndef CONFIG_USE_ICC_SYSREGS_FOR_IRQFLAGS
/* Set priority mask register */
- gic_write_pmr(DEFAULT_PMR_VALUE);
+ gic_write_pmr(ICC_PMR_EL1_UNMASKED);
+#endif

/*
* Some firmwares hand over to the kernel with the BPR changed from
diff --git a/include/linux/irqchip/arm-gic-common.h b/include/linux/irqchip/arm-gic-common.h
index 0a83b43..2c9a4b3 100644
--- a/include/linux/irqchip/arm-gic-common.h
+++ b/include/linux/irqchip/arm-gic-common.h
@@ -13,6 +13,12 @@
#include <linux/types.h>
#include <linux/ioport.h>

+#define GICD_INT_DEF_PRI 0xc0
+#define GICD_INT_DEF_PRI_X4 ((GICD_INT_DEF_PRI << 24) |\
+ (GICD_INT_DEF_PRI << 16) |\
+ (GICD_INT_DEF_PRI << 8) |\
+ GICD_INT_DEF_PRI)
+
enum gic_type {
GIC_V2,
GIC_V3,
diff --git a/include/linux/irqchip/arm-gic.h b/include/linux/irqchip/arm-gic.h
index d3453ee..47f5a8c 100644
--- a/include/linux/irqchip/arm-gic.h
+++ b/include/linux/irqchip/arm-gic.h
@@ -65,11 +65,6 @@
#define GICD_INT_EN_CLR_X32 0xffffffff
#define GICD_INT_EN_SET_SGI 0x0000ffff
#define GICD_INT_EN_CLR_PPI 0xffff0000
-#define GICD_INT_DEF_PRI 0xa0
-#define GICD_INT_DEF_PRI_X4 ((GICD_INT_DEF_PRI << 24) |\
- (GICD_INT_DEF_PRI << 16) |\
- (GICD_INT_DEF_PRI << 8) |\
- GICD_INT_DEF_PRI)

#define GICH_HCR 0x0
#define GICH_VTR 0x4
--
1.9.1