Re: [PATCH 1/2] KVM: VMX: Keep registers read/write consistent with definition

[Paolo Bonzini <pbonzini@redhat.com>]

On 22/04/21 11:34, Yang Zhong wrote:
> The kvm_cache_regs.h file has defined inline functions for those general
> purpose registers and pointer register read/write operations, we need keep
> those related registers operations consistent with header file definition
> in the VMX side.
> 
> Signed-off-by: Yang Zhong <yang.zhong@intel.com>
> ---
>   arch/x86/kvm/vmx/vmx.c | 11 ++++++-----
>   1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 29b40e092d13..d56505fc7a71 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2266,10 +2266,10 @@ static void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
>   
>   	switch (reg) {
>   	case VCPU_REGS_RSP:
> -		vcpu->arch.regs[VCPU_REGS_RSP] = vmcs_readl(GUEST_RSP);
> +		kvm_rsp_write(vcpu, vmcs_readl(GUEST_RSP));
>   		break;
>   	case VCPU_REGS_RIP:
> -		vcpu->arch.regs[VCPU_REGS_RIP] = vmcs_readl(GUEST_RIP);
> +		kvm_rip_write(vcpu, vmcs_readl(GUEST_RIP));
>   		break;

This is on purpose, because you don't want to mark those register dirty.

Likewise, in the case below it's more confusing to go through the helper 
because it checks kvm_register_is_available and calls vmx_cache_reg if 
false.

Because these functions are the once that handle the caching, it makes 
sense for them not to use the helpers.

Paolo

>   	case VCPU_EXREG_PDPTR:
>   		if (enable_ept)
> @@ -4432,7 +4432,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>   
>   	vmx->msr_ia32_umwait_control = 0;
>   
> -	vmx->vcpu.arch.regs[VCPU_REGS_RDX] = get_rdx_init_val();
> +	kvm_rdx_write(&vmx->vcpu, get_rdx_init_val());
>   	vmx->hv_deadline_tsc = -1;
>   	kvm_set_cr8(vcpu, 0);
>   
> @@ -6725,9 +6725,10 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
>   	WARN_ON_ONCE(vmx->nested.need_vmcs12_to_shadow_sync);
>   
>   	if (kvm_register_is_dirty(vcpu, VCPU_REGS_RSP))
> -		vmcs_writel(GUEST_RSP, vcpu->arch.regs[VCPU_REGS_RSP]);
> +		vmcs_writel(GUEST_RSP, kvm_rsp_read(vcpu));
> +
>   	if (kvm_register_is_dirty(vcpu, VCPU_REGS_RIP))
> -		vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]);
> +		vmcs_writel(GUEST_RIP, kvm_rip_read(vcpu));
>   
>   	cr3 = __get_current_cr3_fast();
>   	if (unlikely(cr3 != vmx->loaded_vmcs->host_state.cr3)) {
>