Re: [PATCH 6.17.y 1/2] x86/resctrl: Refactor resctrl_arch_rmid_read()

[Babu Moger <bmoger@amd.com>]

Thank you for back-porting.


On 10/20/25 11:53, Sasha Levin wrote:
> From: Babu Moger <babu.moger@amd.com>
>
> [ Upstream commit 7c9ac605e202c4668e441fc8146a993577131ca1 ]
>
> resctrl_arch_rmid_read() adjusts the value obtained from MSR_IA32_QM_CTR to
> account for the overflow for MBM events and apply counter scaling for all the
> events. This logic is common to both reading an RMID and reading a hardware
> counter directly.
>
> Refactor the hardware value adjustment logic into get_corrected_val() to
> prepare for support of reading a hardware counter.
>
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
> Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com
> Stable-dep-of: 15292f1b4c55 ("x86/resctrl: Fix miscount of bandwidth event when reactivating previously unavailable RMID")
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>   arch/x86/kernel/cpu/resctrl/monitor.c | 38 ++++++++++++++++-----------
>   1 file changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index c261558276cdd..cff5bcaddf42f 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -224,24 +224,13 @@ static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr, unsigned int width)
>   	return chunks >> shift;
>   }
>   
> -int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
> -			   u32 unused, u32 rmid, enum resctrl_event_id eventid,
> -			   u64 *val, void *ignored)
> +static u64 get_corrected_val(struct rdt_resource *r, struct rdt_mon_domain *d,
> +			     u32 rmid, enum resctrl_event_id eventid, u64 msr_val)
>   {
>   	struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
>   	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> -	int cpu = cpumask_any(&d->hdr.cpu_mask);
>   	struct arch_mbm_state *am;
> -	u64 msr_val, chunks;
> -	u32 prmid;
> -	int ret;
> -
> -	resctrl_arch_rmid_read_context_check();
> -
> -	prmid = logical_rmid_to_physical_rmid(cpu, rmid);
> -	ret = __rmid_read_phys(prmid, eventid, &msr_val);
> -	if (ret)
> -		return ret;
> +	u64 chunks;
>   
>   	am = get_arch_mbm_state(hw_dom, rmid, eventid);
>   	if (am) {
> @@ -253,7 +242,26 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
>   		chunks = msr_val;
>   	}
>   
> -	*val = chunks * hw_res->mon_scale;
> +	return chunks * hw_res->mon_scale;
> +}
> +
> +int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
> +			   u32 unused, u32 rmid, enum resctrl_event_id eventid,
> +			   u64 *val, void *ignored)
> +{
> +	int cpu = cpumask_any(&d->hdr.cpu_mask);
> +	u64 msr_val;
> +	u32 prmid;
> +	int ret;
> +
> +	resctrl_arch_rmid_read_context_check();
> +
> +	prmid = logical_rmid_to_physical_rmid(cpu, rmid);
> +	ret = __rmid_read_phys(prmid, eventid, &msr_val);
> +	if (ret)
> +		return ret;
> +
> +	*val = get_corrected_val(r, d, rmid, eventid, msr_val);
>   
>   	return 0;
>   }