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

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Date:   Mon, 6 Mar 2023 11:33:21 +0000
From:   James Morse <james.morse@....com>
To:     Peter Newman <peternewman@...gle.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 Peter,

On 23/01/2023 13:54, Peter Newman wrote:
> 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.

Yup, this is the normal headache when rebasing over other changes.
Thanks for fixing that thing - I thought the 'first' behaviour in the filesystem code
covered it, but clearly it doesn't.


Thanks,

James