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KVM: VMX: Avoid vmwrite(HOST_RSP) when possible 

Usually HOST_RSP retains its value across guest entries.  Take advantage
of this and avoid a vmwrite() when this is so.

Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Avi Kivity 2008-07-17 18:04:30 +03:00
parent 3b4bd7969f
commit 313dbd49dc
1 changed files with 6 additions and 0 deletions
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6
arch/x86/kvm/vmx.c
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@ -58,6 +58,7 @@ struct vmcs {
struct vcpu_vmx {
struct kvm_vcpu vcpu;
struct list_head local_vcpus_link;
unsigned long host_rsp;
int launched;
u8 fail;
u32 idt_vectoring_info;
@ -2982,7 +2983,11 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
/* Store host registers */
"push %%"R"dx; push %%"R"bp;"
"push %%"R"cx \n\t"
"cmp %%"R"sp, %c[host_rsp](%0) \n\t"
"je 1f \n\t"
"mov %%"R"sp, %c[host_rsp](%0) \n\t"
__ex(ASM_VMX_VMWRITE_RSP_RDX) "\n\t"
"1: \n\t"
/* Check if vmlaunch of vmresume is needed */
"cmpl $0, %c[launched](%0) \n\t"
/* Load guest registers. Don't clobber flags. */
@ -3039,6 +3044,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
: : "c"(vmx), "d"((unsigned long)HOST_RSP),
[launched]"i"(offsetof(struct vcpu_vmx, launched)),
[fail]"i"(offsetof(struct vcpu_vmx, fail)),
[host_rsp]"i"(offsetof(struct vcpu_vmx, host_rsp)),
[rax]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RAX])),
[rbx]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RBX])),
[rcx]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RCX])),