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KVM: VMX: Load/save guest CR2 via C code in __vmx_vcpu_run() 

...to eliminate its parameter and struct vcpu_vmx offset definition
from the assembly blob.  Accessing CR2 from C versus assembly doesn't
change the likelihood of taking a page fault (and modifying CR2) while
it's loaded with the guest's value, so long as we don't do anything
silly between accessing CR2 and VM-Enter/VM-Exit.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
hifive-unleashed-5.1
Sean Christopherson 2019-01-25 07:41:03 -08:00 committed by Paolo Bonzini
parent 5a8781607e
commit 47e97c099b
1 changed files with 5 additions and 11 deletions
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16
arch/x86/kvm/vmx/vmx.c
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@ -6375,6 +6375,9 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
if (static_branch_unlikely(&vmx_l1d_should_flush))
vmx_l1d_flush(vcpu);
if (vcpu->arch.cr2 != read_cr2())
write_cr2(vcpu->arch.cr2);
asm(
/* Store host registers */
"push %%" _ASM_BP " \n\t"
@ -6395,13 +6398,6 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
"1: \n\t"
"add $%c[wordsize], %%" _ASM_SP "\n\t" /* un-adjust RSP */
/* Reload cr2 if changed */
"mov %c[cr2](%%" _ASM_CX "), %%" _ASM_AX " \n\t"
"mov %%cr2, %%" _ASM_DX " \n\t"
"cmp %%" _ASM_AX ", %%" _ASM_DX " \n\t"
"je 3f \n\t"
"mov %%" _ASM_AX", %%cr2 \n\t"
"3: \n\t"
/* Check if vmlaunch or vmresume is needed */
"cmpb $0, %c[launched](%%" _ASM_CX ") \n\t"
/* Load guest registers. Don't clobber flags. */
@ -6471,9 +6467,6 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
"xor %%r14d, %%r14d \n\t"
"xor %%r15d, %%r15d \n\t"
#endif
"mov %%cr2, %%" _ASM_AX " \n\t"
"mov %%" _ASM_AX ", %c[cr2](%%" _ASM_CX ") \n\t"
"xor %%eax, %%eax \n\t"
"xor %%ebx, %%ebx \n\t"
"xor %%ecx, %%ecx \n\t"
@ -6504,7 +6497,6 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
[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)),
[wordsize]"i"(sizeof(ulong))
: "cc", "memory"
#ifdef CONFIG_X86_64
@ -6514,6 +6506,8 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
, "eax", "ebx", "edx"
#endif
);
vcpu->arch.cr2 = read_cr2();
}
STACK_FRAME_NON_STANDARD(__vmx_vcpu_run);