[PATCH 5.17 051/225] x86/cpu: Load microcode during restore_processor_state()

From: Greg Kroah-Hartman
Date: Wed May 04 2022 - 13:27:44 EST


From: Borislav Petkov <bp@xxxxxxx>

commit f9e14dbbd454581061c736bf70bf5cbb15ac927c upstream.

When resuming from system sleep state, restore_processor_state()
restores the boot CPU MSRs. These MSRs could be emulated by microcode.
If microcode is not loaded yet, writing to emulated MSRs leads to
unchecked MSR access error:

...
PM: Calling lapic_suspend+0x0/0x210
unchecked MSR access error: WRMSR to 0x10f (tried to write 0x0...0) at rIP: ... (native_write_msr)
Call Trace:
<TASK>
? restore_processor_state
x86_acpi_suspend_lowlevel
acpi_suspend_enter
suspend_devices_and_enter
pm_suspend.cold
state_store
kobj_attr_store
sysfs_kf_write
kernfs_fop_write_iter
new_sync_write
vfs_write
ksys_write
__x64_sys_write
do_syscall_64
entry_SYSCALL_64_after_hwframe
RIP: 0033:0x7fda13c260a7

To ensure microcode emulated MSRs are available for restoration, load
the microcode on the boot CPU before restoring these MSRs.

[ Pawan: write commit message and productize it. ]

Fixes: e2a1256b17b1 ("x86/speculation: Restore speculation related MSRs during S3 resume")
Reported-by: Kyle D. Pelton <kyle.d.pelton@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Tested-by: Kyle D. Pelton <kyle.d.pelton@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215841
Link: https://lore.kernel.org/r/4350dfbf785cd482d3fafa72b2b49c83102df3ce.1650386317.git.pawan.kumar.gupta@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/microcode.h | 2 ++
arch/x86/kernel/cpu/microcode/core.c | 6 +++---
arch/x86/power/cpu.c | 10 +++++++++-
3 files changed, 14 insertions(+), 4 deletions(-)

--- a/arch/x86/include/asm/microcode.h
+++ b/arch/x86/include/asm/microcode.h
@@ -131,10 +131,12 @@ extern void __init load_ucode_bsp(void);
extern void load_ucode_ap(void);
void reload_early_microcode(void);
extern bool initrd_gone;
+void microcode_bsp_resume(void);
#else
static inline void __init load_ucode_bsp(void) { }
static inline void load_ucode_ap(void) { }
static inline void reload_early_microcode(void) { }
+static inline void microcode_bsp_resume(void) { }
#endif

#endif /* _ASM_X86_MICROCODE_H */
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -758,9 +758,9 @@ static struct subsys_interface mc_cpu_in
};

/**
- * mc_bp_resume - Update boot CPU microcode during resume.
+ * microcode_bsp_resume - Update boot CPU microcode during resume.
*/
-static void mc_bp_resume(void)
+void microcode_bsp_resume(void)
{
int cpu = smp_processor_id();
struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
@@ -772,7 +772,7 @@ static void mc_bp_resume(void)
}

static struct syscore_ops mc_syscore_ops = {
- .resume = mc_bp_resume,
+ .resume = microcode_bsp_resume,
};

static int mc_cpu_starting(unsigned int cpu)
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -25,6 +25,7 @@
#include <asm/cpu.h>
#include <asm/mmu_context.h>
#include <asm/cpu_device_id.h>
+#include <asm/microcode.h>

#ifdef CONFIG_X86_32
__visible unsigned long saved_context_ebx;
@@ -262,11 +263,18 @@ static void notrace __restore_processor_
x86_platform.restore_sched_clock_state();
mtrr_bp_restore();
perf_restore_debug_store();
- msr_restore_context(ctxt);

c = &cpu_data(smp_processor_id());
if (cpu_has(c, X86_FEATURE_MSR_IA32_FEAT_CTL))
init_ia32_feat_ctl(c);
+
+ microcode_bsp_resume();
+
+ /*
+ * This needs to happen after the microcode has been updated upon resume
+ * because some of the MSRs are "emulated" in microcode.
+ */
+ msr_restore_context(ctxt);
}

/* Needed by apm.c */