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Message-ID: <f020defb-df73-35ff-5d97-c07773bafb67@amd.com>
Date:   Fri, 23 Sep 2022 21:55:02 +0530
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Subject: Re: [PATCH v2] x86,acpi: Limit "Dummy wait" workaround to older AMD
 and Intel processors
Content-Language: en-US
To:     Borislav Petkov <bp@alien8.de>
Cc:     linux-kernel@vger.kernel.org, rafael@kernel.org, lenb@kernel.org,
        linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org,
        dave.hansen@linux.intel.com, tglx@linutronix.de, andi@lisas.de,
        puwen@hygon.cn, mario.limonciello@amd.com, peterz@infradead.org,
        rui.zhang@intel.com, gpiccoli@igalia.com,
        daniel.lezcano@linaro.org, ananth.narayan@amd.com,
        gautham.shenoy@amd.com, Calvin Ong <calvin.ong@amd.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        stable@vger.kernel.org
References: <20220923153801.9167-1-kprateek.nayak@amd.com>
 <Yy3U0fQ0GZYZnMa1@zn.tnic>
From:   K Prateek Nayak <kprateek.nayak@amd.com>
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Hello Boris,

On 9/23/2022 9:16 PM, Borislav Petkov wrote:
> On Fri, Sep 23, 2022 at 09:08:01PM +0530, K Prateek Nayak wrote:
>> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
>> index ef4775c6db01..fcd3617ed315 100644
>> --- a/arch/x86/include/asm/cpufeatures.h
>> +++ b/arch/x86/include/asm/cpufeatures.h
>> @@ -460,5 +460,6 @@
>>  #define X86_BUG_MMIO_UNKNOWN		X86_BUG(26) /* CPU is too old and its MMIO Stale Data status is unknown */
>>  #define X86_BUG_RETBLEED		X86_BUG(27) /* CPU is affected by RETBleed */
>>  #define X86_BUG_EIBRS_PBRSB		X86_BUG(28) /* EIBRS is vulnerable to Post Barrier RSB Predictions */
>> +#define X86_BUG_STPCLK			X86_BUG(29) /* STPCLK# signal does not get asserted in time during IOPORT based C-state entry */
> 
> What for?
> 
> Did you not see this thread?
> 
> https://lore.kernel.org/r/78d13a19-2806-c8af-573e-7f2625edfab8@intel.com
> 

Yes, I did see the patch, but Andreas replied to Dave's patch attached
in v1 saying that he had seen this issue with AMD Athlon on a VIA
chipset back in 2006. (https://lore.kernel.org/lkml/Yyy6l94G0O2B7Yh1@rhlx01.hs-esslingen.de/)
Therefore, Dave's patch is not sufficient.

Dave suggested the use of AMD vendor and family check, but Peter then
pointed out that we would also need the Hygon vendor check.

Hence I worked on the v2 which addressed these with the help of
X86_BUG_STPCLK so that we can avoid vendor specific checks inside the
common acpi code.
--
Thanks and Regards,
Prateek