From: Andy Lutomirski <luto@kernel.org>
To: "Luck, Tony" <tony.luck@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>
Cc: "Yu, Fenghua" <fenghua.yu@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>, H Peter Anvin <hpa@zytor.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
Christoph Hellwig <hch@infradead.org>,
Peter Zijlstra <peterz@infradead.org>,
David Woodhouse <dwmw2@infradead.org>,
Lu Baolu <baolu.lu@linux.intel.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
Randy Dunlap <rdunlap@infradead.org>,
"Raj, Ashok" <ashok.raj@intel.com>,
"Pan, Jacob jun" <jacob.jun.pan@intel.com>,
"Jiang, Dave" <dave.jiang@intel.com>,
"Mehta, Sohil" <sohil.mehta@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>
Subject: Re: [PATCH] x86/cpufeatures: Force disable X86_FEATURE_ENQCMD and remove update_pasid()
Date: Thu, 3 Jun 2021 10:31:36 -0700 [thread overview]
Message-ID: <db552f51-76ee-b7f5-20f1-14f1c703d423@kernel.org> (raw)
In-Reply-To: <36866b38ec92425b879881a88acf547b@intel.com>
On 6/2/21 1:37 PM, Luck, Tony wrote:
>>> ... so on a PASID system, your trivial reproducer would theoretically
>>> fire the same way and corrupt FPU state just as well.
>>
>> This is worse and you can't selftest it because the IPI can just hit in
>> the middle of _any_ FPU state operation and corrupt state.
>
> That sounds like we should abandon the "IPI all the other threads
> to force enable the PASID for them" approach. It would just be a
> nightmare of papering over cracks when the IPI was delivered at
> some inconvenient moment when the recipient was in the middle
> of touching xsave state.
>
> I've told Fenghua to dig out the previous iteration of this patch where
> the plan was to lazily fix the PASID_MSR in other threads in the #GP
> handler.
Blech. Also this won't work for other PASID-like features.
I have a half-written patch to fix this up for real. Stay tuned.
> Seems like a better direction than trying to fix the IPI method. The virtualization
> folks will like this way more because IPI in guest causes a couple of VMEXIT
> so is somewhat expensive.
It happens at most once per PASID-using process.
next prev parent reply other threads:[~2021-06-03 17:31 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1600187413-163670-1-git-send-email-fenghua.yu@intel.com>
2020-09-15 16:30 ` [PATCH v8 2/9] iommu/vt-d: Change flags type to unsigned int in binding mm Fenghua Yu
2020-09-18 7:42 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2020-09-15 16:30 ` [PATCH v8 4/9] x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions Fenghua Yu
2020-09-18 7:42 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2020-09-15 16:30 ` [PATCH v8 5/9] x86/fpu/xstate: Add supervisor PASID state for ENQCMD feature Fenghua Yu
2020-09-18 7:42 ` [tip: x86/pasid] x86/fpu/xstate: Add supervisor PASID state for ENQCMD tip-bot2 for Yu-cheng Yu
2020-09-15 16:30 ` [PATCH v8 6/9] x86/msr-index: Define IA32_PASID MSR Fenghua Yu
2020-09-18 7:42 ` [tip: x86/pasid] x86/msr-index: Define an " tip-bot2 for Fenghua Yu
2020-09-15 16:30 ` [PATCH v8 9/9] x86/mmu: Allocate/free PASID Fenghua Yu
2020-09-18 7:42 ` [tip: x86/pasid] x86/mmu: Allocate/free a PASID tip-bot2 for Fenghua Yu
2021-05-29 9:17 ` [PATCH] x86/cpufeatures: Force disable X86_FEATURE_ENQCMD and remove update_pasid() Thomas Gleixner
2021-05-31 8:43 ` Borislav Petkov
2021-05-31 10:16 ` Thomas Gleixner
2021-06-02 20:37 ` Luck, Tony
2021-06-03 17:31 ` Andy Lutomirski [this message]
2021-06-09 17:32 ` Luck, Tony
2021-06-09 23:34 ` Andy Lutomirski
2021-06-25 15:46 ` Luck, Tony
2021-06-02 10:14 ` Borislav Petkov
2021-06-02 10:20 ` Thomas Gleixner
2021-06-03 11:20 ` Vinod Koul
2021-06-03 11:42 ` Borislav Petkov
2021-06-03 12:47 ` Vinod Koul
2021-06-03 14:33 ` Borislav Petkov
2021-06-02 19:49 ` [tip: x86/urgent] " tip-bot2 for Thomas Gleixner
2021-06-03 14:38 ` tip-bot2 for Thomas Gleixner
2020-09-16 8:06 ` [PATCH v8 0/9] x86: tag application address space for devices Joerg Roedel
2020-09-17 23:53 ` Fenghua Yu
[not found] ` <1600187413-163670-4-git-send-email-fenghua.yu@intel.com>
2020-09-17 7:53 ` [PATCH v8 3/9] Documentation/x86: Add documentation for SVA (Shared Virtual Addressing) Borislav Petkov
2020-09-17 14:56 ` Raj, Ashok
2020-09-17 17:18 ` Borislav Petkov
2020-09-17 17:22 ` Raj, Ashok
2020-09-17 17:30 ` Borislav Petkov
2020-09-18 16:22 ` Fenghua Yu
2020-09-18 7:42 ` [tip: x86/pasid] " tip-bot2 for Ashok Raj
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