linux-kernel - Re: [PATCH 2/2] KVM: TDX: Do not clear poisoned pages

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Message-ID: <2c8075f0-2817-4895-a509-bcf1a0771bff@intel.com>
Date: Wed, 25 Jun 2025 09:57:07 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Tony Luck <tony.luck@...el.com>, pbonzini@...hat.com, seanjc@...gle.com,
 Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, H Peter Anvin <hpa@...or.com>, linux-edac@...r.kernel.org,
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 kirill.shutemov@...ux.intel.com, kai.huang@...el.com,
 reinette.chatre@...el.com, xiaoyao.li@...el.com,
 tony.lindgren@...ux.intel.com, binbin.wu@...ux.intel.com,
 isaku.yamahata@...el.com, yan.y.zhao@...el.com, chao.gao@...el.com,
 Vishal Annapurve <vannapurve@...gle.com>, rick.p.edgecombe@...el.com
Subject: Re: [PATCH 2/2] KVM: TDX: Do not clear poisoned pages

On 6/25/25 09:42, Adrian Hunter wrote:
> On 25/06/2025 19:31, Dave Hansen wrote:
>> On 6/25/25 09:25, Adrian Hunter wrote:
>>>> IIUC, even if movdir64b stores contents on hwpoisoned pages, it's not
>>>> going to cause any trouble.
>>> No.  PageHWPoison(page) means the page should not be touched.  It must
>>> be freed back to the allocator where it will never be allocated again.
>>
>> What's the end-user-visible effect if the page is touched in this
>> specific function in this specific way (with movdir64b)?
>>
>> In other words, what does this patch do for end users?
> 
> We have another patch that clarifies that.  It turns out we need
> to clear pages (MOVDIR64B) only if the platform has the so-called
> partial-write errata X86_BUG_TDX_PW_MCE.
> 
> It was decided to deal with that issue separately, but maybe it
> needs to bundled in the same patch set, now that the discussion
> has moved in that direction?

It sure sounds like it to me.