Re: [PATCH v4 1/2] x86/vtx: add LBR_SELECT to the list of LBR MSRs

[Jan Beulich <jbeulich@xxxxxxxx>]

On 14.04.2021 06:40, Igor Druzhinin wrote:
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2915,14 +2915,16 @@ static const struct lbr_info {
>  }, nh_lbr[] = {
>      { MSR_IA32_LASTINTFROMIP,       1 },
>      { MSR_IA32_LASTINTTOIP,         1 },
> -    { MSR_C2_LASTBRANCH_TOS,        1 },
> +    { MSR_NHL_LBR_SELECT,           1 },
> +    { MSR_NHL_LASTBRANCH_TOS,       1 },
>      { MSR_P4_LASTBRANCH_0_FROM_LIP, NUM_MSR_P4_LASTBRANCH_FROM_TO },
>      { MSR_P4_LASTBRANCH_0_TO_LIP,   NUM_MSR_P4_LASTBRANCH_FROM_TO },
>      { 0, 0 }
>  }, sk_lbr[] = {
>      { MSR_IA32_LASTINTFROMIP,       1 },
>      { MSR_IA32_LASTINTTOIP,         1 },
> -    { MSR_SKL_LASTBRANCH_TOS,       1 },
> +    { MSR_NHL_LBR_SELECT,           1 },
> +    { MSR_NHL_LASTBRANCH_TOS,       1 },
>      { MSR_SKL_LASTBRANCH_0_FROM_IP, NUM_MSR_SKL_LASTBRANCH },
>      { MSR_SKL_LASTBRANCH_0_TO_IP,   NUM_MSR_SKL_LASTBRANCH },
>      { MSR_SKL_LASTBRANCH_0_INFO,    NUM_MSR_SKL_LASTBRANCH },
> @@ -2937,6 +2939,7 @@ static const struct lbr_info {
>  }, gm_lbr[] = {
>      { MSR_IA32_LASTINTFROMIP,       1 },
>      { MSR_IA32_LASTINTTOIP,         1 },
> +    { MSR_GM_LBR_SELECT,            1 },

What about Xeon Phi, Silvermont, and Airmont?

> --- a/xen/include/asm-x86/msr-index.h
> +++ b/xen/include/asm-x86/msr-index.h
> @@ -606,14 +606,18 @@
>  #define NUM_MSR_C2_LASTBRANCH_FROM_TO        4
>  #define NUM_MSR_ATOM_LASTBRANCH_FROM_TO      8
>  
> +/* Nehalem (and newer) last-branch recording */
> +#define MSR_NHL_LBR_SELECT           0x000001c8
> +#define MSR_NHL_LASTBRANCH_TOS               0x000001c9
> +
>  /* Skylake (and newer) last-branch recording */
> -#define MSR_SKL_LASTBRANCH_TOS               0x000001c9
>  #define MSR_SKL_LASTBRANCH_0_FROM_IP 0x00000680
>  #define MSR_SKL_LASTBRANCH_0_TO_IP   0x000006c0
>  #define MSR_SKL_LASTBRANCH_0_INFO    0x00000dc0
>  #define NUM_MSR_SKL_LASTBRANCH               32
>  
>  /* Goldmont last-branch recording */
> +#define MSR_GM_LBR_SELECT            0x000001c8
>  #define MSR_GM_LASTBRANCH_TOS                0x000001c9

Wouldn't it make sense to also re-use the NHL constants, like you
do for Skylake?

Jan