From ff593e5abebd899b0b41c11280e2fbeff4103375 Mon Sep 17 00:00:00 2001 From: Laurent Vivier Date: Thu, 25 Oct 2007 14:18:55 +0200 Subject: [PATCH] KVM: VMX: Let gcc to choose which registers to save (i386) 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 Signed-off-by: Avi Kivity --- drivers/kvm/vmx.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c index 56c9bcc82836..2d7d638d72d0 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 ); -- 2.20.1