From 40712faeb84dacfcb3925a88231daa08b3624d34 Mon Sep 17 00:00:00 2001 From: Avi Kivity <avi@redhat.com> Date: Thu, 6 Jan 2011 18:09:12 +0200 Subject: [PATCH] KVM: VMX: Avoid atomic operation in vmx_vcpu_run Instead of exchanging the guest and host rcx, have separate storage for each. This allows us to avoid using the xchg instruction, which is is a little slower than normal operations. Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> --- arch/x86/kvm/vmx.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index da468c26639d..ae4f02d47091 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -4022,6 +4022,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) asm( /* Store host registers */ "push %%"R"dx; push %%"R"bp;" + "push %%"R"cx \n\t" /* placeholder for guest rcx */ "push %%"R"cx \n\t" "cmp %%"R"sp, %c[host_rsp](%0) \n\t" "je 1f \n\t" @@ -4063,7 +4064,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) ".Llaunched: " __ex(ASM_VMX_VMRESUME) "\n\t" ".Lkvm_vmx_return: " /* Save guest registers, load host registers, keep flags */ - "xchg %0, (%%"R"sp) \n\t" + "mov %0, %c[wordsize](%%"R"sp) \n\t" + "pop %0 \n\t" "mov %%"R"ax, %c[rax](%0) \n\t" "mov %%"R"bx, %c[rbx](%0) \n\t" "pop"Q" %c[rcx](%0) \n\t" @@ -4107,7 +4109,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) [r14]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_R14])), [r15]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_R15])), #endif - [cr2]"i"(offsetof(struct vcpu_vmx, vcpu.arch.cr2)) + [cr2]"i"(offsetof(struct vcpu_vmx, vcpu.arch.cr2)), + [wordsize]"i"(sizeof(ulong)) : "cc", "memory" , R"ax", R"bx", R"di", R"si" #ifdef CONFIG_X86_64 -- GitLab