linux-kernel - Re: [PATCH 1/2] x86/mce: Fix missing address mask in recovery for errors in TDX/SEAM non-root mode

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Message-ID: <79eca29a-8ba4-4ad9-b2e0-54d8e668f731@intel.com>
Date: Fri, 27 Jun 2025 09:33:18 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>,
 "Hunter, Adrian" <adrian.hunter@...el.com>
Cc: "Annapurve, Vishal" <vannapurve@...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" <x86@...nel.org>, H Peter Anvin <hpa@...or.com>,
 "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
 "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
 "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
 "Huang, Kai" <kai.huang@...el.com>,
 "Chatre, Reinette" <reinette.chatre@...el.com>,
 "Li, Xiaoyao" <xiaoyao.li@...el.com>,
 "tony.lindgren@...ux.intel.com" <tony.lindgren@...ux.intel.com>,
 "binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>,
 "Yamahata, Isaku" <isaku.yamahata@...el.com>,
 "Zhao, Yan Y" <yan.y.zhao@...el.com>, "Gao, Chao" <chao.gao@...el.com>,
 "pbonzini@...hat.com" <pbonzini@...hat.com>,
 "seanjc@...gle.com" <seanjc@...gle.com>
Subject: Re: [PATCH 1/2] x86/mce: Fix missing address mask in recovery for
 errors in TDX/SEAM non-root mode

On 6/27/25 09:24, Luck, Tony wrote:
> We've been sending a combined key+address in the "mce->addr" to
> user space for a while. Has anyone built infrastructure on top of that?

I'm not sure they can do anything useful with an address that has the
KeyID in the first place. The partitioning scheme is in an MSR, so
they'd need to be doing silly gymnastics to even decode the address.

Userspace can deal with the KeyID not being in the address. It's been
the default for ages. So, if we take it back out, I'd expect it fixes
more things than it breaks.

So, yeah, we should carefully consider it. But it still 100% looks like
the right thing to me to detangle the KeyID and physical address in the ABI.