linux-kernel - Re: [PATCH] perf/x86/intel/uncore: Enable uncore on vCPUs when using uncore discovery

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Message-ID: <73e999cd-93c3-49e0-bac2-0e2c6efe4110@linux.intel.com>
Date: Tue, 24 Sep 2024 09:51:01 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: 陈培鸿(乘鸿) <chenpeihong.cph@...baba-inc.com>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>, Thomas Gleixner
 <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86 <x86@...nel.org>,
 "H. Peter Anvin" <hpa@...or.com>,
 linux-perf-users <linux-perf-users@...r.kernel.org>,
 linux-kernel <linux-kernel@...r.kernel.org>
Cc: 郑翔(正翔) <zx283061@...baba-inc.com>,
 赵生龙 <shenglong.zsl@...baba-inc.com>
Subject: Re: [PATCH] perf/x86/intel/uncore: Enable uncore on vCPUs when using
 uncore discovery

On 2024-09-23 10:47 p.m., 陈培鸿(乘鸿) wrote:
> With uncore discovery, kvm can choose to expose a subset of
> uncore related MSRs it wants to guest by emulate the uncore
> discovery device. 

I don't hear that the KVM has started to support uncore vPMU.
Can you please point me to patches?

The default of uncore_no_discover is 0. So it bypasses the HYPERVISOR
check unless the user specially sets the value. It could be a problem
for the earlier platforms which don't support discovery
table. How do you plan to emulate the devices on earlier platforms?

Thanks,
Kan
> So we can enable uncore on virtualized CPUs
> when uncore discovery is using.
> Signed-off-by: Cheng Hong <chenpeihong.cph@...baba-inc.com>
> ---
>  arch/x86/events/intel/uncore.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index d98fac567684..33776df95aa4 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -1920,7 +1920,7 @@ static int __init intel_uncore_init(void)
>  struct intel_uncore_init_fun *uncore_init;
>  int pret = 0, cret = 0, mret = 0, ret;
> - if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
> + if (uncore_no_discover && boot_cpu_has(X86_FEATURE_HYPERVISOR))
>  return -ENODEV;
>  __uncore_max_dies =