Messages in this thread Patch in this message | | | From | Avi Kivity <> | Subject | [PATCH 12/55] KVM: VMX: Let gcc to choose which registers to save (i386) | Date | Wed, 26 Dec 2007 13:05:17 +0200 |
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From: Laurent Vivier <Laurent.Vivier@bull.net>
This patch lets GCC to determine which registers to save when we switch to/from a VCPU in the case of intel i386.
* Original code saves following registers:
eax, ebx, ecx, edx, edi, esi, ebp (using popa)
* Patched code:
- informs GCC that we modify following registers using the clobber description:
ebx, edi, rsi
- doesn't save eax because it is an output operand (vmx->fail)
- cannot put ecx in clobber description because it is an input operand, but as we modify it and we want to keep its value (vcpu), we must save it (pop/push)
- ebp is saved (pop/push) because GCC seems to ignore its use the clobber description.
- edx is saved (pop/push) because it is reserved by GCC (REGPARM) and cannot be put in the clobber description.
- line "mov (%%esp), %3 \n\t" has been removed because %3 is ecx and ecx is restored just after.
Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net> Signed-off-by: Avi Kivity <avi@qumranet.com> --- drivers/kvm/vmx.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c index 3a58a2a..f76677d 100644 --- a/drivers/kvm/vmx.c +++ b/drivers/kvm/vmx.c @@ -2268,7 +2268,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) "push %%rdx; push %%rbp;" "push %%rcx \n\t" #else - "pusha; push %%ecx \n\t" + "push %%edx; push %%ebp;" + "push %%ecx \n\t" #endif ASM_VMX_VMWRITE_RSP_RDX "\n\t" /* Check if vmlaunch of vmresume is needed */ @@ -2342,9 +2343,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) "mov %%ebp, %c[rbp](%3) \n\t" "mov %%cr2, %%eax \n\t" "mov %%eax, %c[cr2](%3) \n\t" - "mov (%%esp), %3 \n\t" - "pop %%ecx; popa \n\t" + "pop %%ecx; pop %%ebp; pop %%edx \n\t" #endif "setbe %0 \n\t" : "=q" (vmx->fail) @@ -2372,6 +2372,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) #ifdef CONFIG_X86_64 , "rbx", "rdi", "rsi" , "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15" +#else + , "ebx", "edi", "rsi" #endif ); -- 1.5.3.7
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