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[2001:b011:380f:3c42:1844:8b0c:6a55:1ec2]) by smtp.gmail.com with ESMTPSA id 127sm20201005pfy.56.2019.10.01.08.47.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 01 Oct 2019 08:47:12 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3594.4.18\)) Subject: Re: [PATCH] x86/hpet: Disable HPET on Intel Coffe Lake From: Kai-Heng Feng In-Reply-To: Date: Tue, 1 Oct 2019 23:47:09 +0800 Cc: Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , harry.pan@intel.com, x86@kernel.org, LKML , Dave Hansen Content-Transfer-Encoding: 8BIT Message-Id: References: <20190829091232.15065-1-kai.heng.feng@canonical.com> <793CCD4F-35E0-46B9-B5D4-3D3233BA5D35@canonical.com> To: Thomas Gleixner X-Mailer: Apple Mail (2.3594.4.18) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, > On Aug 30, 2019, at 03:45, Thomas Gleixner wrote: > > On Thu, 29 Aug 2019, Kai-Heng Feng wrote: >> at 20:13, Thomas Gleixner wrote: >>> On Thu, 29 Aug 2019, Kai-Heng Feng wrote: >>> >>>> Some Coffee Lake platforms have skewed HPET timer once the SoCs entered >>>> PC10, and marked TSC as unstable clocksource as result. >>> >>> So here you talk about Coffee Lake and in the patch you use KABYLAKE. >> >> Coffeelake has the same model number as Kabylake. > > Yeah, just a bit more text explaining that would be helpful. > >>>> +static const struct x86_cpu_id hpet_blacklist[] __initconst = { >>>> + { X86_VENDOR_INTEL, 6, INTEL_FAM6_KABYLAKE_MOBILE }, >>>> + { X86_VENDOR_INTEL, 6, INTEL_FAM6_KABYLAKE_DESKTOP }, >>> >>> So this disables HPET on all Kaby Lake variants not just on the affected >>> Coffee Lakes. I know that I rejected the initial patch with the random >>> stepping cutoff... >>> >>> https://lore.kernel.org/lkml/alpine.DEB.2.21.1904081403220.1748@nanos.tec.linutronix.de >>> >>> In the other attempt to 'fix' this I asked for clarification, but silence >>> from Intel after this: >>> >>> https://lore.kernel.org/lkml/alpine.DEB.2.21.1905182015320.3019@nanos.tec.linutronix.de >>> >>> Can Intel please provide some useful information about this finally? >> >> Hopefully Intel can provide more info. >> >> I know we should find the root cause rather than stopping at "it’s a firmware >> bug”, but users are already affected by this issue [1]. >> Is there any better short-term workaround? > > Not really. And if Intel stays silent, I'm just going to apply it as is > along with a stable tag. Seems like there's still no updates from Intel. Can we have this patch in v5.4? Kai-Heng > > Thanks, > > tglx