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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>
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@ -6363,15 +6363,18 @@ static void vmx_update_hv_timer(struct kvm_vcpu *vcpu)
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vmx->loaded_vmcs->hv_timer_armed = false;
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}
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void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
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{
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if (unlikely(host_rsp != vmx->loaded_vmcs->host_state.rsp)) {
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vmx->loaded_vmcs->host_state.rsp = host_rsp;
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vmcs_writel(HOST_RSP, host_rsp);
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}
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}
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static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
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{
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unsigned long evmcs_rsp;
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vmx->__launched = vmx->loaded_vmcs->launched;
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evmcs_rsp = static_branch_unlikely(&enable_evmcs) ?
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(unsigned long)¤t_evmcs->host_rsp : 0;
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if (static_branch_unlikely(&vmx_l1d_should_flush))
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vmx_l1d_flush(vcpu);
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@ -6382,21 +6385,14 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
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/* Store host registers */
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"push %%" _ASM_BP " \n\t"
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"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* placeholder for guest RCX */
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"push %%" _ASM_CX " \n\t"
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"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* temporarily adjust RSP for CALL */
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"cmp %%" _ASM_SP ", (%%" _ASM_DI ") \n\t"
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"je 1f \n\t"
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"mov %%" _ASM_SP ", (%%" _ASM_DI ") \n\t"
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/* Avoid VMWRITE when Enlightened VMCS is in use */
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"test %%" _ASM_SI ", %%" _ASM_SI " \n\t"
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"jz 2f \n\t"
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"mov %%" _ASM_SP ", (%%" _ASM_SI ") \n\t"
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"jmp 1f \n\t"
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"2: \n\t"
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"mov $%c[HOST_RSP], %%" _ASM_DX " \n\t"
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__ex("vmwrite %%" _ASM_SP ", %%" _ASM_DX) "\n\t"
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"1: \n\t"
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"add $%c[wordsize], %%" _ASM_SP "\n\t" /* un-adjust RSP */
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"push %%" _ASM_ARG1 " \n\t"
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/* Adjust RSP to account for the CALL to vmx_vmenter(). */
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"lea -%c[wordsize](%%" _ASM_SP "), %%" _ASM_ARG2 " \n\t"
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"call vmx_update_host_rsp \n\t"
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/* Load the vcpu_vmx pointer to RCX. */
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"mov (%%" _ASM_SP "), %%" _ASM_CX " \n\t"
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/* Check if vmlaunch or vmresume is needed */
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"cmpb $0, %c[launched](%%" _ASM_CX ") \n\t"
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@ -6475,11 +6471,16 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
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"xor %%edi, %%edi \n\t"
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"xor %%ebp, %%ebp \n\t"
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"pop %%" _ASM_BP " \n\t"
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: ASM_CALL_CONSTRAINT, "=D"((int){0}), "=S"((int){0})
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: "c"(vmx), "D"(&vmx->loaded_vmcs->host_state.rsp), "S"(evmcs_rsp),
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: ASM_CALL_CONSTRAINT,
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#ifdef CONFIG_X86_64
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"=D"((int){0})
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: "D"(vmx),
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#else
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"=a"((int){0})
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: "a"(vmx),
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#endif
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[launched]"i"(offsetof(struct vcpu_vmx, __launched)),
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[fail]"i"(offsetof(struct vcpu_vmx, fail)),
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[HOST_RSP]"i"(HOST_RSP),
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[rax]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RAX])),
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[rbx]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RBX])),
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[rcx]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RCX])),
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@ -6500,10 +6501,10 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
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[wordsize]"i"(sizeof(ulong))
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: "cc", "memory"
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#ifdef CONFIG_X86_64
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, "rax", "rbx", "rdx"
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, "rax", "rbx", "rcx", "rdx", "rsi"
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, "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"
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#else
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, "eax", "ebx", "edx"
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, "ebx", "ecx", "edx", "edi", "esi"
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#endif
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);
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