Re: [RFC PATCH v2 12/34] x86/msr: Remove pmu_msr_{read,write}()

["Mi, Dapeng" <dapeng1.mi@linux.intel.com>]

On 4/22/2025 4:21 PM, Xin Li (Intel) wrote:
> As pmu_msr_{read,write}() are now wrappers of pmu_msr_chk_emulated(),
> remove them and use pmu_msr_chk_emulated() directly.
>
> While at it, convert the data type of MSR index to u32 in functions
> called in pmu_msr_chk_emulated().
>
> Suggested-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Signed-off-by: Xin Li (Intel) <xin@zytor.com>
> ---
>  arch/x86/xen/enlighten_pv.c | 17 ++++++++++-------
>  arch/x86/xen/pmu.c          | 24 ++++--------------------
>  arch/x86/xen/xen-ops.h      |  3 +--
>  3 files changed, 15 insertions(+), 29 deletions(-)
>
> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> index 1418758b57ff..b5a8bceb5f56 100644
> --- a/arch/x86/xen/enlighten_pv.c
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -1089,8 +1089,9 @@ static void xen_write_cr4(unsigned long cr4)
>  static u64 xen_do_read_msr(unsigned int msr, int *err)
>  {
>  	u64 val = 0;	/* Avoid uninitialized value for safe variant. */
> +	bool emulated;
>  
> -	if (pmu_msr_read(msr, &val, err))
> +	if (pmu_msr_chk_emulated(msr, &val, true, &emulated) && emulated)

ah, here it is.

Could we merge this patch and previous patch into a single patch? It's
unnecessary to just modify the pmu_msr_read()/pmu_msr_write() in previous
patch and delete them immediately. It just wastes the effort.


>  		return val;
>  
>  	if (err)
> @@ -1133,6 +1134,7 @@ static void xen_do_write_msr(unsigned int msr, unsigned int low,
>  			     unsigned int high, int *err)
>  {
>  	u64 val;
> +	bool emulated;
>  
>  	switch (msr) {
>  	case MSR_FS_BASE:
> @@ -1162,12 +1164,13 @@ static void xen_do_write_msr(unsigned int msr, unsigned int low,
>  	default:
>  		val = (u64)high << 32 | low;
>  
> -		if (!pmu_msr_write(msr, val)) {
> -			if (err)
> -				*err = native_write_msr_safe(msr, low, high);
> -			else
> -				native_write_msr(msr, low, high);
> -		}
> +		if (pmu_msr_chk_emulated(msr, &val, false, &emulated) && emulated)
> +			return;
> +
> +		if (err)
> +			*err = native_write_msr_safe(msr, low, high);
> +		else
> +			native_write_msr(msr, low, high);
>  	}
>  }
>  
> diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c
> index 95caae97a394..afb02f43ee3f 100644
> --- a/arch/x86/xen/pmu.c
> +++ b/arch/x86/xen/pmu.c
> @@ -128,7 +128,7 @@ static inline uint32_t get_fam15h_addr(u32 addr)
>  	return addr;
>  }
>  
> -static inline bool is_amd_pmu_msr(unsigned int msr)
> +static bool is_amd_pmu_msr(u32 msr)
>  {
>  	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
>  	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
> @@ -194,8 +194,7 @@ static bool is_intel_pmu_msr(u32 msr_index, int *type, int *index)
>  	}
>  }
>  
> -static bool xen_intel_pmu_emulate(unsigned int msr, u64 *val, int type,
> -				  int index, bool is_read)
> +static bool xen_intel_pmu_emulate(u32 msr, u64 *val, int type, int index, bool is_read)
>  {
>  	uint64_t *reg = NULL;
>  	struct xen_pmu_intel_ctxt *ctxt;
> @@ -257,7 +256,7 @@ static bool xen_intel_pmu_emulate(unsigned int msr, u64 *val, int type,
>  	return false;
>  }
>  
> -static bool xen_amd_pmu_emulate(unsigned int msr, u64 *val, bool is_read)
> +static bool xen_amd_pmu_emulate(u32 msr, u64 *val, bool is_read)
>  {
>  	uint64_t *reg = NULL;
>  	int i, off = 0;
> @@ -298,8 +297,7 @@ static bool xen_amd_pmu_emulate(unsigned int msr, u64 *val, bool is_read)
>  	return false;
>  }
>  
> -static bool pmu_msr_chk_emulated(unsigned int msr, uint64_t *val, bool is_read,
> -				 bool *emul)
> +bool pmu_msr_chk_emulated(u32 msr, u64 *val, bool is_read, bool *emul)
>  {
>  	int type, index = 0;
>  
> @@ -313,20 +311,6 @@ static bool pmu_msr_chk_emulated(unsigned int msr, uint64_t *val, bool is_read,
>  	return true;
>  }
>  
> -bool pmu_msr_read(u32 msr, u64 *val)
> -{
> -	bool emulated;
> -
> -	return pmu_msr_chk_emulated(msr, val, true, &emulated) && emulated;
> -}
> -
> -bool pmu_msr_write(u32 msr, u64 val)
> -{
> -	bool emulated;
> -
> -	return pmu_msr_chk_emulated(msr, &val, false, &emulated) && emulated;
> -}
> -
>  static u64 xen_amd_read_pmc(int counter)
>  {
>  	struct xen_pmu_amd_ctxt *ctxt;
> diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
> index a1875e10be31..fde9f9d7415f 100644
> --- a/arch/x86/xen/xen-ops.h
> +++ b/arch/x86/xen/xen-ops.h
> @@ -271,8 +271,7 @@ void xen_pmu_finish(int cpu);
>  static inline void xen_pmu_init(int cpu) {}
>  static inline void xen_pmu_finish(int cpu) {}
>  #endif
> -bool pmu_msr_read(u32 msr, u64 *val);
> -bool pmu_msr_write(u32 msr, u64 val);
> +bool pmu_msr_chk_emulated(u32 msr, u64 *val, bool is_read, bool *emul);
>  int pmu_apic_update(uint32_t reg);
>  u64 xen_read_pmc(int counter);
>