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KVM: VMX: Update VMCS.HOST_RSP via helper C function 

Providing a helper function to update HOST_RSP is visibly easier to
read, and more importantly (for the future) eliminates two arguments to
the VM-Enter assembly blob.  Reducing the number of arguments to the asm
blob is for all intents and purposes a prerequisite to moving the code
to a proper assembly routine.  It's not truly mandatory, but it greatly
simplifies the future code, and the cost of the extra CALL+RET is
negligible in the grand scheme.

Note that although _ASM_ARG[1-3] can be used in the inline asm itself,
the intput/output constraints need to be manually defined.  gcc will
actually compile with _ASM_ARG[1-3] specified as constraints, but what
it actually ends up doing with the bogus constraint is unknown.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
hifive-unleashed-5.1
Sean Christopherson 2019-01-25 07:41:04 -08:00 committed by Paolo Bonzini
parent 47e97c099b
commit c09b03eb7f
1 changed files with 26 additions and 25 deletions
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51
arch/x86/kvm/vmx/vmx.c
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@ -6363,15 +6363,18 @@ static void vmx_update_hv_timer(struct kvm_vcpu *vcpu)
vmx->loaded_vmcs->hv_timer_armed = false;
}
void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
{
if (unlikely(host_rsp != vmx->loaded_vmcs->host_state.rsp)) {
vmx->loaded_vmcs->host_state.rsp = host_rsp;
vmcs_writel(HOST_RSP, host_rsp);
}
}
static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
{
unsigned long evmcs_rsp;
vmx->__launched = vmx->loaded_vmcs->launched;
evmcs_rsp = static_branch_unlikely(&enable_evmcs) ?
(unsigned long)&current_evmcs->host_rsp : 0;
if (static_branch_unlikely(&vmx_l1d_should_flush))
vmx_l1d_flush(vcpu);
@ -6382,21 +6385,14 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
/* Store host registers */
"push %%" _ASM_BP " \n\t"
"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* placeholder for guest RCX */
"push %%" _ASM_CX " \n\t"
"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* temporarily adjust RSP for CALL */
"cmp %%" _ASM_SP ", (%%" _ASM_DI ") \n\t"
"je 1f \n\t"
"mov %%" _ASM_SP ", (%%" _ASM_DI ") \n\t"
/* Avoid VMWRITE when Enlightened VMCS is in use */
"test %%" _ASM_SI ", %%" _ASM_SI " \n\t"
"jz 2f \n\t"
"mov %%" _ASM_SP ", (%%" _ASM_SI ") \n\t"
"jmp 1f \n\t"
"2: \n\t"
"mov $%c[HOST_RSP], %%" _ASM_DX " \n\t"
__ex("vmwrite %%" _ASM_SP ", %%" _ASM_DX) "\n\t"
"1: \n\t"
"add $%c[wordsize], %%" _ASM_SP "\n\t" /* un-adjust RSP */
"push %%" _ASM_ARG1 " \n\t"
/* Adjust RSP to account for the CALL to vmx_vmenter(). */
"lea -%c[wordsize](%%" _ASM_SP "), %%" _ASM_ARG2 " \n\t"
"call vmx_update_host_rsp \n\t"
/* Load the vcpu_vmx pointer to RCX. */
"mov (%%" _ASM_SP "), %%" _ASM_CX " \n\t"
/* Check if vmlaunch or vmresume is needed */
"cmpb $0, %c[launched](%%" _ASM_CX ") \n\t"
@ -6475,11 +6471,16 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
"xor %%edi, %%edi \n\t"
"xor %%ebp, %%ebp \n\t"
"pop %%" _ASM_BP " \n\t"
: ASM_CALL_CONSTRAINT, "=D"((int){0}), "=S"((int){0})
: "c"(vmx), "D"(&vmx->loaded_vmcs->host_state.rsp), "S"(evmcs_rsp),
: ASM_CALL_CONSTRAINT,
#ifdef CONFIG_X86_64
"=D"((int){0})
: "D"(vmx),
#else
"=a"((int){0})
: "a"(vmx),
#endif
[launched]"i"(offsetof(struct vcpu_vmx, __launched)),
[fail]"i"(offsetof(struct vcpu_vmx, fail)),
[HOST_RSP]"i"(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])),
@ -6500,10 +6501,10 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
[wordsize]"i"(sizeof(ulong))
: "cc", "memory"
#ifdef CONFIG_X86_64
, "rax", "rbx", "rdx"
, "rax", "rbx", "rcx", "rdx", "rsi"
, "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"
#else
, "eax", "ebx", "edx"
, "ebx", "ecx", "edx", "edi", "esi"
#endif
);