From: Dave Hansen <dave.hansen@intel.com>
To: Wyes Karny <wyes.karny@amd.com>, linux-kernel@vger.kernel.org
Cc: Lewis.Carroll@amd.com, Mario.Limonciello@amd.com,
gautham.shenoy@amd.com, Ananth.Narayan@amd.com, bharata@amd.com,
len.brown@intel.com, x86@kernel.org, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
hpa@zytor.com, peterz@infradead.org, chang.seok.bae@intel.com,
keescook@chromium.org, metze@samba.org,
zhengqi.arch@bytedance.com, mark.rutland@arm.com, puwen@hygon.cn,
rafael.j.wysocki@intel.com, andrew.cooper3@citrix.com,
jing2.liu@intel.com, jmattson@google.com,
pawan.kumar.gupta@linux.intel.com
Subject: Re: [PATCH v2 2/3] x86: Remove vendor checks from prefer_mwait_c1_over_halt
Date: Fri, 6 May 2022 08:52:03 -0700 [thread overview]
Message-ID: <1a806ced-4bb9-c18f-e614-75e9d9722d08@intel.com> (raw)
In-Reply-To: <fa4e26df-d2e7-7b13-a961-4f741b319e79@amd.com>
On 5/6/22 02:42, Wyes Karny wrote:
>
> So, if CPUID.05H:ECX[0] = 0, MWAIT extensions are not available (not allowed) and hence
> it is safe to use MWAIT with EAX=0,ECX=0. Otherwise, we have to check CPUID.05H:EDX[bit 7:4]
> to get the number of C1 substates and this should be greater than equal to 1.
Ahh, I misread the comment. I was confusing the CPUID leaf ECX data
with the use of ECX hints to MWAIT.
Could you add maybe a sentence or two more in that comment to help
clarify the situation?
next prev parent reply other threads:[~2022-05-06 15:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-05 10:48 [PATCH v2 0/3] x86: Prefer MWAIT over HALT on AMD processors Wyes Karny
2022-05-05 10:48 ` [PATCH v2 1/3] x86: Use HALT in default_idle when idle=nomwait cmdline arg is passed Wyes Karny
2022-05-05 17:13 ` Dave Hansen
2022-05-06 11:23 ` Wyes Karny
2022-05-05 11:01 ` [PATCH v2 2/3] x86: Remove vendor checks from prefer_mwait_c1_over_halt Wyes Karny
2022-05-05 17:04 ` Dave Hansen
2022-05-06 9:42 ` Wyes Karny
2022-05-06 15:52 ` Dave Hansen [this message]
2022-05-06 18:19 ` Wyes Karny
2022-05-05 11:04 ` [PATCH v2 3/3] x86: Fix comment for X86_FEATURE_ZEN Wyes Karny
2022-05-05 17:10 ` Dave Hansen
2022-05-05 18:55 ` Wyes Karny
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