[RFC PATCH 16/33] Add support for Xen to entry.S.

From: Chris Wright
Date: Tue Jul 18 2006 - 05:24:08 EST

- change cli/sti
- change test for user mode return to work for kernel mode in ring1
- check hypervisor saved event mask on return from exception
- add entry points for the hypervisor upcall handlers
- avoid math emulation check when running on Xen
- add nmi handler for running on Xen

Signed-off-by: Ian Pratt <ian.pratt@xxxxxxxxxxxxx>
Signed-off-by: Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>

---
arch/i386/kernel/asm-offsets.c | 26 +++++++
arch/i386/kernel/entry.S | 141 ++++++++++++++++++++++++++++++++++++-----
arch/i386/mach-xen/setup-xen.c | 19 +++++
drivers/xen/core/features.c | 2
4 files changed, 169 insertions(+), 19 deletions(-)

diff -r 5cca1805b8a7 arch/i386/kernel/entry.S
--- a/arch/i386/kernel/entry.S Tue Jul 18 02:20:39 2006 -0400
+++ b/arch/i386/kernel/entry.S Tue Jul 18 02:22:56 2006 -0400
@@ -76,8 +76,39 @@ NT_MASK = 0x00004000
NT_MASK = 0x00004000
VM_MASK = 0x00020000

+#ifndef CONFIG_XEN
+#define DISABLE_INTERRUPTS cli
+#define ENABLE_INTERRUPTS sti
+#else
+#include <xen/interface/xen.h>
+
+EVENT_MASK = 0x2E
+
+/* Offsets into shared_info_t. */
+#define evtchn_upcall_pending /* 0 */
+#define evtchn_upcall_mask 1
+
+#ifdef CONFIG_SMP
+/* Set %esi to point to the appropriate vcpu structure */
+#define GET_VCPU_INFO movl TI_cpu(%ebp),%esi ; \
+ shl $SIZEOF_VCPU_INFO_SHIFT,%esi ; \
+ addl HYPERVISOR_shared_info,%esi
+#else
+#define GET_VCPU_INFO movl HYPERVISOR_shared_info,%esi
+#endif
+
+/* The following end up using/clobbering %esi, because of GET_VCPU_INFO */
+#define __DISABLE_INTERRUPTS movb $1,evtchn_upcall_mask(%esi)
+#define DISABLE_INTERRUPTS GET_VCPU_INFO ; \
+ __DISABLE_INTERRUPTS
+#define ENABLE_INTERRUPTS GET_VCPU_INFO ; \
+ movb $0,evtchn_upcall_mask(%esi)
+#define __TEST_PENDING testb $0xFF,evtchn_upcall_pending(%esi)
+#endif
+
+
#ifdef CONFIG_PREEMPT
-#define preempt_stop cli; TRACE_IRQS_OFF
+#define preempt_stop DISABLE_INTERRUPTS; TRACE_IRQS_OFF
#else
#define preempt_stop
#define resume_kernel restore_nocheck
@@ -229,10 +260,10 @@ check_userspace:
check_userspace:
movl EFLAGS(%esp), %eax # mix EFLAGS and CS
movb CS(%esp), %al
- testl $(VM_MASK | 3), %eax
+ testl $(VM_MASK | USER_MODE_MASK), %eax
jz resume_kernel
ENTRY(resume_userspace)
- cli # make sure we don't miss an interrupt
+ DISABLE_INTERRUPTS # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
movl TI_flags(%ebp), %ecx
@@ -243,7 +274,7 @@ ENTRY(resume_userspace)

#ifdef CONFIG_PREEMPT
ENTRY(resume_kernel)
- cli
+ DISABLE_INTERRUPTS
cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ?
jnz restore_nocheck
need_resched:
@@ -271,7 +302,7 @@ sysenter_past_esp:
* No need to follow this irqs on/off section: the syscall
* disabled irqs and here we enable it straight after entry:
*/
- sti
+ ENABLE_INTERRUPTS
pushl $(__USER_DS)
CFI_ADJUST_CFA_OFFSET 4
/*CFI_REL_OFFSET ss, 0*/
@@ -316,7 +347,7 @@ 1: movl (%ebp),%ebp
jae syscall_badsys
call *sys_call_table(,%eax,4)
movl %eax,EAX(%esp)
- cli
+ DISABLE_INTERRUPTS
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
testw $_TIF_ALLWORK_MASK, %cx
@@ -326,7 +357,7 @@ 1: movl (%ebp),%ebp
movl OLDESP(%esp), %ecx
xorl %ebp,%ebp
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS
sysexit
CFI_ENDPROC

@@ -352,7 +383,7 @@ syscall_call:
call *sys_call_table(,%eax,4)
movl %eax,EAX(%esp) # store the return value
syscall_exit:
- cli # make sure we don't miss an interrupt
+ DISABLE_INTERRUPTS # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
@@ -361,6 +392,7 @@ syscall_exit:
jne syscall_exit_work

restore_all:
+#ifndef CONFIG_XEN
movl EFLAGS(%esp), %eax # mix EFLAGS, SS and CS
# Warning: OLDSS(%esp) contains the wrong/random values if we
# are returning to the kernel.
@@ -372,6 +404,27 @@ restore_all:
CFI_REMEMBER_STATE
je ldt_ss # returning to user-space with LDT SS
restore_nocheck:
+#else
+restore_nocheck:
+ /* Return back to the hypervisor if we're not returning to user-mode */
+ movl EFLAGS(%esp), %eax # mix EFLAGS and CS
+ movb CS(%esp), %al
+ andl $(VM_MASK | 3), %eax
+ cmpl $3, %eax
+ jne hypervisor_iret
+ ENABLE_INTERRUPTS
+ __TEST_PENDING
+ jz restore_regs_and_iret
+ __DISABLE_INTERRUPTS
+ jmp do_hypervisor_callback
+hypervisor_iret:
+ TRACE_IRQS_IRET
+ RESTORE_REGS
+ addl $4, %esp
+ CFI_ADJUST_CFA_OFFSET -4
+ jmp hypercall_page + (__HYPERVISOR_iret * 32)
+#endif /* CONFIG_XEN */
+restore_regs_and_iret:
TRACE_IRQS_IRET
restore_nocheck_notrace:
RESTORE_REGS
@@ -380,8 +433,10 @@ 1: iret
1: iret
.section .fixup,"ax"
iret_exc:
+#ifndef CONFIG_XEN
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS
+#endif
pushl $0 # no error code
pushl $do_iret_error
jmp error_code
@@ -392,6 +447,7 @@ iret_exc:
.previous

CFI_RESTORE_STATE
+#ifndef CONFIG_XEN
ldt_ss:
larl OLDSS(%esp), %eax
jnz restore_nocheck
@@ -405,7 +461,7 @@ ldt_ss:
* dosemu and wine happy. */
subl $8, %esp # reserve space for switch16 pointer
CFI_ADJUST_CFA_OFFSET 8
- cli
+ DISABLE_INTERRUPTS
TRACE_IRQS_OFF
movl %esp, %eax
/* Set up the 16bit stack frame with switch32 pointer on top,
@@ -420,6 +476,7 @@ 1: iret
.align 4
.long 1b,iret_exc
.previous
+#endif
CFI_ENDPROC

# perform work that needs to be done immediately before resumption
@@ -430,7 +487,7 @@ work_pending:
jz work_notifysig
work_resched:
call schedule
- cli # make sure we don't miss an interrupt
+ DISABLE_INTERRUPTS # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
@@ -486,7 +543,7 @@ syscall_exit_work:
testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP), %cl
jz work_pending
TRACE_IRQS_ON
- sti # could let do_syscall_trace() call
+ ENABLE_INTERRUPTS # could let do_syscall_trace() call
# schedule() instead
movl %esp, %eax
movl $1, %edx
@@ -508,6 +565,7 @@ syscall_badsys:
jmp resume_userspace
CFI_ENDPROC

+#ifndef CONFIG_XEN
#define FIXUP_ESPFIX_STACK \
movl %esp, %eax; \
/* switch to 32bit stack using the pointer on top of 16bit stack */ \
@@ -586,6 +644,9 @@ ENTRY(name) \

/* The include is where all of the SMP etc. interrupts come from */
#include "entry_arch.h"
+#else
+#define UNWIND_ESPFIX_STACK
+#endif

ENTRY(divide_error)
RING0_INT_FRAME
@@ -642,6 +703,44 @@ error_code:
jmp ret_from_exception
CFI_ENDPROC

+#ifdef CONFIG_XEN
+ENTRY(hypervisor_callback)
+ pushl %eax
+ SAVE_ALL
+do_hypervisor_callback:
+ push %esp
+ call evtchn_do_upcall
+ add $4,%esp
+ jmp ret_from_intr
+
+# Hypervisor uses this for application faults while it executes.
+ENTRY(failsafe_callback)
+1: popl %ds
+2: popl %es
+3: popl %fs
+4: popl %gs
+ subl $4,%esp
+ SAVE_ALL
+ jmp ret_from_exception
+.section .fixup,"ax"; \
+6: movl $0,(%esp); \
+ jmp 1b; \
+7: movl $0,(%esp); \
+ jmp 2b; \
+8: movl $0,(%esp); \
+ jmp 3b; \
+9: movl $0,(%esp); \
+ jmp 4b; \
+.previous; \
+.section __ex_table,"a";\
+ .align 4; \
+ .long 1b,6b; \
+ .long 2b,7b; \
+ .long 3b,8b; \
+ .long 4b,9b; \
+.previous
+#endif
+
ENTRY(coprocessor_error)
RING0_INT_FRAME
pushl $0
@@ -665,18 +764,20 @@ ENTRY(device_not_available)
pushl $-1 # mark this as an int
CFI_ADJUST_CFA_OFFSET 4
SAVE_ALL
+#ifndef CONFIG_XEN
movl %cr0, %eax
testl $0x4, %eax # EM (math emulation bit)
- jne device_not_available_emulate
- preempt_stop
- call math_state_restore
- jmp ret_from_exception
-device_not_available_emulate:
+ je device_available_emulate
pushl $0 # temporary storage for ORIG_EIP
CFI_ADJUST_CFA_OFFSET 4
call math_emulate
addl $4, %esp
CFI_ADJUST_CFA_OFFSET -4
+ jmp ret_from_exception
+device_available_emulate:
+#endif
+ preempt_stop
+ call math_state_restore
jmp ret_from_exception
CFI_ENDPROC

@@ -717,6 +818,8 @@ debug_stack_correct:
jmp ret_from_exception
CFI_ENDPROC
.previous .text
+
+#ifndef CONFIG_XEN
/*
* NMI is doubly nasty. It can happen _while_ we're handling
* a debug fault, and the debug fault hasn't yet been able to
@@ -801,6 +904,10 @@ 1: iret
.align 4
.long 1b,iret_exc
.previous
+#else
+ENTRY(nmi)
+ jmp restore_all
+#endif

KPROBE_ENTRY(int3)
RING0_INT_FRAME
diff -r 5cca1805b8a7 arch/i386/mach-xen/setup-xen.c
--- a/arch/i386/mach-xen/setup-xen.c Tue Jul 18 02:20:39 2006 -0400
+++ b/arch/i386/mach-xen/setup-xen.c Tue Jul 18 02:22:56 2006 -0400
@@ -40,7 +40,26 @@ char * __init machine_specific_memory_se

void __init machine_specific_arch_setup(void)
{
+ struct physdev_op op;
+
setup_xen_features();
+
+ HYPERVISOR_shared_info =
+ (struct shared_info *)__va(xen_start_info->shared_info);
+ memset(empty_zero_page, 0, sizeof(empty_zero_page));
+
+ HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_4gb_segments);
+
+ HYPERVISOR_set_callbacks(
+ __KERNEL_CS, (unsigned long)hypervisor_callback,
+ __KERNEL_CS, (unsigned long)failsafe_callback);
+
+ init_pg_tables_end = __pa(xen_start_info->pt_base) +
+ PFN_PHYS(xen_start_info->nr_pt_frames);
+
+ op.cmd = PHYSDEVOP_SET_IOPL;
+ op.u.set_iopl.iopl = 1;
+ HYPERVISOR_physdev_op(&op);

#ifdef CONFIG_ACPI
if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
diff -r 5cca1805b8a7 drivers/xen/core/features.c
--- a/drivers/xen/core/features.c Tue Jul 18 02:20:39 2006 -0400
+++ b/drivers/xen/core/features.c Tue Jul 18 02:22:56 2006 -0400
@@ -16,7 +16,6 @@ EXPORT_SYMBOL_GPL(xen_features);

void setup_xen_features(void)
{
-#if 0 /* hypercalls come later in the series */
struct xen_feature_info fi;
int i, j;

@@ -27,5 +26,4 @@ void setup_xen_features(void)
for (j=0; j<32; j++)
xen_features[i*32+j] = !!(fi.submap & 1<<j);
}
-#endif
}
diff -r 5cca1805b8a7 arch/i386/kernel/asm-offsets.c
--- a/arch/i386/kernel/asm-offsets.c Tue Jul 18 02:20:39 2006 -0400
+++ b/arch/i386/kernel/asm-offsets.c Tue Jul 18 02:22:56 2006 -0400
@@ -15,6 +15,7 @@
#include <asm/processor.h>
#include <asm/thread_info.h>
#include <asm/elf.h>
+#include <xen/interface/xen.h>

#define DEFINE(sym, val) \
asm volatile("\n->" #sym " %0 " #val : : "i" (val))
@@ -23,6 +24,27 @@

#define OFFSET(sym, str, mem) \
DEFINE(sym, offsetof(struct str, mem));
+
+/* return log2(const) computed at compile time */
+extern inline int get_shift(const int x)
+{
+ extern int __bad_size_in_get_shift(void);
+ if (__builtin_constant_p(x)) {
+ switch(x) {
+ case 1: return 0;
+ case 2: return 1;
+ case 4: return 2;
+ case 8: return 3;
+ case 16: return 4;
+ case 32: return 5;
+ case 64: return 6;
+ case 128: return 7;
+ case 256: return 8;
+ }
+ }
+
+ return __bad_size_in_get_shift();
+}

void foo(void)
{
@@ -74,4 +96,8 @@ void foo(void)
DEFINE(VDSO_PRELINK, VDSO_PRELINK);

OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx);
+
+ BLANK();
+ DEFINE(SIZEOF_VCPU_INFO, sizeof(struct vcpu_info));
+ DEFINE(SIZEOF_VCPU_INFO_SHIFT, get_shift(sizeof(struct vcpu_info)));
}

--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/