linux-kernel - Re: [PATCH v2 09/18] x86/resctrl: Allow resctrl_arch_rmid

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Date:   Mon, 23 Jan 2023 14:54:53 +0100
From:   Peter Newman <peternewman@...gle.com>
To:     James Morse <james.morse@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        shameerali.kolothum.thodi@...wei.com,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        carl@...amperecomputing.com, lcherian@...vell.com,
        bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
        xingxin.hx@...nanolis.org, baolin.wang@...ux.alibaba.com,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>
Subject: Re: [PATCH v2 09/18] x86/resctrl: Allow resctrl_arch_rmid_read() to sleep

Hi James,

On Fri, Jan 13, 2023 at 6:56 PM James Morse <james.morse@....com> wrote:
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index d309b830aeb2..d6ae4b713801 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -206,17 +206,19 @@ 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_domain *d,
> -                          u32 closid, u32 rmid, enum resctrl_event_id eventid,
> -                          u64 *val)
> +struct __rmid_read_arg
>  {
> -       struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> -       struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
> -       struct arch_mbm_state *am;
> -       u64 msr_val, chunks;
> +       u32 rmid;
> +       enum resctrl_event_id eventid;
>
> -       if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask))
> -               return -EINVAL;
> +       u64 msr_val;
> +};
> +
> +static void __rmid_read(void *arg)
> +{
> +       enum resctrl_event_id eventid = ((struct __rmid_read_arg *)arg)->eventid;
> +       u32 rmid = ((struct __rmid_read_arg *)arg)->rmid;
> +       u64 msr_val;
>
>         /*
>          * As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured
> @@ -229,6 +231,28 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
>         wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
>         rdmsrl(MSR_IA32_QM_CTR, msr_val);
>
> +       ((struct __rmid_read_arg *)arg)->msr_val = msr_val;
> +}
> +
> +int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
> +                          u32 closid, u32 rmid, enum resctrl_event_id eventid,
> +                          u64 *val)
> +{
> +       struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> +       struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
> +       struct __rmid_read_arg arg;
> +       struct arch_mbm_state *am;
> +       u64 msr_val, chunks;
> +       int err;
> +
> +       arg.rmid = rmid;
> +       arg.eventid = eventid;
> +
> +       err = smp_call_function_any(&d->cpu_mask, __rmid_read, &arg, true);
> +       if (err)
> +               return err;
> +
> +       msr_val = arg.msr_val;

These changes are conflicting now after v6.2-rc4 due to my recent
changes in resctrl_arch_rmid_read(), which include my own
reintroduction of __rmid_read():

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=2a81160d29d65b5876ab3f824fda99ae0219f05e

Fortunately it looks like our respective versions of __rmid_read()
aren't too much different from the original, but __rmid_read() does
have a new call site in resctrl_arch_reset_rmid() to record initial
event counts.

-Peter