On 20.05.2022 15:37, Roger Pau Monne wrote:
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -3007,6 +3007,8 @@ static const struct lbr_info {
> { MSR_GM_LASTBRANCH_0_FROM_IP, NUM_MSR_GM_LASTBRANCH_FROM_TO },
> { MSR_GM_LASTBRANCH_0_TO_IP, NUM_MSR_GM_LASTBRANCH_FROM_TO },
> { 0, 0 }
> +}, no_lbr[] = {
> + {0, 0}
> };
Instead of introducing this and ...
> @@ -3070,6 +3072,21 @@ static const struct lbr_info *last_branch_msr_get(void)
> /* Goldmont */
> case 0x5c: case 0x5f:
> return gm_lbr;
> +
> + default:
> + if ( cpu_has_pdcm )
> + {
> + uint64_t cap;
> +
> + rdmsrl(MSR_IA32_PERF_CAPABILITIES, cap);
> + if ( (cap & MSR_IA32_PERF_CAP_LBR_FORMAT) == 0x3f )
> + /*
> + * On processors that do not support model-specific LBRs,
> + * PERF_CAPABILITIES.LBR_FMT will have the value 0x3f.
> + */
> + return no_lbr;
... doing this MSR read every time, can't you store a mask value
once during boot, which you apply to msr_content ...
> @@ -3521,6 +3538,8 @@ static int cf_check vmx_msr_write_intercept(
> return X86EMUL_OKAY;
> }
>
> + if ( lbr->count )
> + {
> for ( ; lbr->count; lbr++ )
> {
> unsigned int i;
... ahead of the bigger if() enclosing this code (thus also avoiding
the need to re-indent)?
Jan
