Re: [PATCH v7 11/26] KVM: x86: Add kvm_msr_{read,write}() helpers

[Maxim Levitsky <mlevitsk@redhat.com>]

On Fri, 2023-11-24 at 00:53 -0500, Yang Weijiang wrote:
> Wrap __kvm_{get,set}_msr() into two new helpers for KVM usage and use the
> helpers to replace existing usage of the raw functions.
> kvm_msr_{read,write}() are KVM-internal helpers, i.e. used when KVM needs
> to get/set a MSR value for emulating CPU behavior, i.e., host_initiated ==
> %true in the helpers.
> 
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  3 ++-
>  arch/x86/kvm/cpuid.c            |  2 +-
>  arch/x86/kvm/x86.c              | 16 +++++++++++++---
>  3 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 5cfa18aaf33f..499bd42e3a32 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1966,9 +1966,10 @@ void kvm_prepare_emulation_failure_exit(struct kvm_vcpu *vcpu);
>  
>  void kvm_enable_efer_bits(u64);
>  bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer);
> -int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data, bool host_initiated);
>  int kvm_emulate_msr_read(struct kvm_vcpu *vcpu, u32 index, u64 *data);
>  int kvm_emulate_msr_write(struct kvm_vcpu *vcpu, u32 index, u64 data);
> +int kvm_msr_read(struct kvm_vcpu *vcpu, u32 index, u64 *data);
> +int kvm_msr_write(struct kvm_vcpu *vcpu, u32 index, u64 data);
>  int kvm_emulate_rdmsr(struct kvm_vcpu *vcpu);
>  int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu);
>  int kvm_emulate_as_nop(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index d0315e469d92..0351e311168a 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -1527,7 +1527,7 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
>  		*edx = entry->edx;
>  		if (function == 7 && index == 0) {
>  			u64 data;
> -		        if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) &&
> +		        if (!kvm_msr_read(vcpu, MSR_IA32_TSX_CTRL, &data) &&
>  			    (data & TSX_CTRL_CPUID_CLEAR))
>  				*ebx &= ~(F(RTM) | F(HLE));
>  		} else if (function == 0x80000007) {
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 16b4f2dd138a..360f4b8a4944 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1917,8 +1917,8 @@ static int kvm_set_msr_ignored_check(struct kvm_vcpu *vcpu,
>   * Returns 0 on success, non-0 otherwise.
>   * Assumes vcpu_load() was already called.
>   */
> -int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data,
> -		  bool host_initiated)
> +static int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data,
> +			 bool host_initiated)
>  {
>  	struct msr_data msr;
>  	int ret;
> @@ -1944,6 +1944,16 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data,
>  	return ret;
>  }
>  
> +int kvm_msr_write(struct kvm_vcpu *vcpu, u32 index, u64 data)
> +{
> +	return __kvm_set_msr(vcpu, index, data, true);
> +}
> +
> +int kvm_msr_read(struct kvm_vcpu *vcpu, u32 index, u64 *data)
> +{
> +	return __kvm_get_msr(vcpu, index, data, true);
> +}
> +
>  static int kvm_get_msr_ignored_check(struct kvm_vcpu *vcpu,
>  				     u32 index, u64 *data, bool host_initiated)
>  {
> @@ -12224,7 +12234,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>  						  MSR_IA32_MISC_ENABLE_BTS_UNAVAIL;
>  
>  		__kvm_set_xcr(vcpu, 0, XFEATURE_MASK_FP);
> -		__kvm_set_msr(vcpu, MSR_IA32_XSS, 0, true);
> +		kvm_msr_write(vcpu, MSR_IA32_XSS, 0);
>  	}
>  
>  	/* All GPRs except RDX (handled below) are zeroed on RESET/INIT. */

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
	Maxim Levitsky