From: Peter Zijlstra <peterz@infradead.org>
To: Dongli Si <kvmx86@gmail.com>
Cc: joro@8bytes.org, liam.merwick@oracle.com, kim.phillips@amd.com,
mingo@kernel.org, acme@kernel.org, mark.rutland@arm.com,
alexander.shishkin@linux.intel.com, jolsa@kernel.org,
namhyung@kernel.org, tglx@linutronix.de, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] perf/x86/amd: Don't touch the Host-only bit inside the guest hypervisor
Date: Thu, 24 Mar 2022 11:42:17 +0100 [thread overview]
Message-ID: <20220324104217.GE8939@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20220320002106.1800166-1-sidongli1997@gmail.com>
On Sun, Mar 20, 2022 at 08:21:06AM +0800, Dongli Si wrote:
> @@ -1027,7 +1028,8 @@ void amd_pmu_enable_virt(void)
> {
> struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
>
> - cpuc->perf_ctr_virt_mask = 0;
> + if (hypervisor_is_type(X86_HYPER_NATIVE))
> + cpuc->perf_ctr_virt_mask = 0;
So I had to go and read the original commit to figure out wth this code
is supposed to be doing. I'm thinking this all can use a wee comment.
Also, the above is very ambiguous as to what it does. Specifically if we
don't set perf_ctr_virt_mask, then what is the actual value (yes, I
know, but its not very clear is it). Also, if we don't in fact change
perf_ctr_virt_mask then these following two lines:
>
> /* Reload all events */
> amd_pmu_disable_all();
amd_pmu_enable_all(0);
are somewhat completely pointless, no?
So can we please get a patch that clarifies things instead of making
things even more obscure?
next prev parent reply other threads:[~2022-03-24 10:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-20 0:21 [PATCH v4] perf/x86/amd: Don't touch the Host-only bit inside the guest hypervisor Dongli Si
2022-03-24 10:42 ` Peter Zijlstra [this message]
2022-03-27 10:56 ` Dongli Si
2022-03-28 14:03 ` Peter Zijlstra
2022-04-01 8:29 ` Dongli Si
2022-04-01 13:06 ` Peter Zijlstra
2022-04-11 13:40 ` Dongli Si
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