# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1294994093 0
# Node ID 4b7cb21caf0e114c5f6ef8a74c17ca799873e83b
# Parent 93e7bf0e1845f1a82441fb740522a9b9cb32beda
x86: Avoid calling xsave_alloc_save_area before xsave_init
Currently, xsave_alloc_save_area will be called in
init_idle_domain->scheduler_init->alloc_vcpu->vcpu_initialise calls
with xsave_cntxt_size=0, it is earlier than xsave_init called in
identity_cpu(). This may causing buffer overflow on xmem_pool.
Idle domain isn't using FPU,SSE,AVX or any such extended state and
doesn't need it saved. xsave_{alloc,free}_save_area() should
test-and-exit on is_idle_vcpu(), and our context switch code should
not be doing XSAVE when switching out an idle vcpu.
Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>
Signed-off-by: Keir Fraser <keir@xxxxxxx>
---
xen/arch/x86/i387.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
xen/include/asm-x86/i387.h | 32 +-------------------------------
2 files changed, 43 insertions(+), 33 deletions(-)
diff -r 93e7bf0e1845 -r 4b7cb21caf0e xen/arch/x86/i387.c
--- a/xen/arch/x86/i387.c Fri Jan 14 08:11:46 2011 +0000
+++ b/xen/arch/x86/i387.c Fri Jan 14 08:34:53 2011 +0000
@@ -16,6 +16,39 @@
#include <asm/i387.h>
#include <asm/asm_defns.h>
+void setup_fpu(struct vcpu *v)
+{
+ ASSERT(!is_idle_vcpu(v));
+
+ /* Avoid recursion. */
+ clts();
+
+ if ( !v->fpu_dirtied )
+ {
+ v->fpu_dirtied = 1;
+ if ( cpu_has_xsave )
+ {
+ if ( !v->fpu_initialised )
+ v->fpu_initialised = 1;
+
+ /* XCR0 normally represents what guest OS set. In case of Xen
+ * itself, we set all supported feature mask before doing
+ * save/restore.
+ */
+ set_xcr0(v->arch.xcr0_accum);
+ xrstor(v);
+ set_xcr0(v->arch.xcr0);
+ }
+ else
+ {
+ if ( v->fpu_initialised )
+ restore_fpu(v);
+ else
+ init_fpu();
+ }
+ }
+}
+
void init_fpu(void)
{
asm volatile ( "fninit" );
@@ -28,6 +61,8 @@ void save_init_fpu(struct vcpu *v)
{
unsigned long cr0 = read_cr0();
char *fpu_ctxt = v->arch.guest_context.fpu_ctxt.x;
+
+ ASSERT(!is_idle_vcpu(v));
/* This can happen, if a paravirtualised guest OS has set its CR0.TS. */
if ( cr0 & X86_CR0_TS )
@@ -138,6 +173,7 @@ void restore_fpu(struct vcpu *v)
}
#define XSTATE_CPUID 0xd
+#define XSAVE_AREA_MIN_SIZE (512 + 64) /* FP/SSE + XSAVE.HEADER */
/*
* Maximum size (in byte) of the XSAVE/XRSTOR save area required by all
@@ -177,7 +213,9 @@ void xsave_init(void)
}
/* FP/SSE, XSAVE.HEADER, YMM */
- min_size = 512 + 64 + ((eax & XSTATE_YMM) ? XSTATE_YMM_SIZE : 0);
+ min_size = XSAVE_AREA_MIN_SIZE;
+ if ( eax & XSTATE_YMM )
+ min_size += XSTATE_YMM_SIZE;
BUG_ON(ecx < min_size);
/*
@@ -214,8 +252,10 @@ int xsave_alloc_save_area(struct vcpu *v
{
void *save_area;
- if ( !cpu_has_xsave )
+ if ( !cpu_has_xsave || is_idle_vcpu(v) )
return 0;
+
+ BUG_ON(xsave_cntxt_size < XSAVE_AREA_MIN_SIZE);
/* XSAVE/XRSTOR requires the save area be 64-byte-boundary aligned. */
save_area = _xmalloc(xsave_cntxt_size, 64);
diff -r 93e7bf0e1845 -r 4b7cb21caf0e xen/include/asm-x86/i387.h
--- a/xen/include/asm-x86/i387.h Fri Jan 14 08:11:46 2011 +0000
+++ b/xen/include/asm-x86/i387.h Fri Jan 14 08:34:53 2011 +0000
@@ -110,6 +110,7 @@ static inline void xrstor(struct vcpu *v
: "m" (*ptr), "a" (-1), "d" (-1), "D"(ptr));
}
+extern void setup_fpu(struct vcpu *v);
extern void init_fpu(void);
extern void save_init_fpu(struct vcpu *v);
extern void restore_fpu(struct vcpu *v);
@@ -124,35 +125,4 @@ extern void restore_fpu(struct vcpu *v);
__asm__ __volatile__ ( "ldmxcsr %0" : : "m" (__mxcsr) ); \
} while ( 0 )
-static inline void setup_fpu(struct vcpu *v)
-{
- /* Avoid recursion. */
- clts();
-
- if ( !v->fpu_dirtied )
- {
- v->fpu_dirtied = 1;
- if ( cpu_has_xsave )
- {
- if ( !v->fpu_initialised )
- v->fpu_initialised = 1;
-
- /* XCR0 normally represents what guest OS set. In case of Xen
- * itself, we set all supported feature mask before doing
- * save/restore.
- */
- set_xcr0(v->arch.xcr0_accum);
- xrstor(v);
- set_xcr0(v->arch.xcr0);
- }
- else
- {
- if ( v->fpu_initialised )
- restore_fpu(v);
- else
- init_fpu();
- }
- }
-}
-
#endif /* __ASM_I386_I387_H */
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