linux-kernel - Re: [PATCH RESEND V2 1/2] x86/mce: Fix missing address mask in recovery for errors in TDX/SEAM non-root mode

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Message-ID: <20250819213247.GJaKTtf1er-Ced_mzP@fat_crate.local>
Date: Tue, 19 Aug 2025 23:32:47 +0200
From: Borislav Petkov <bp@...en8.de>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>, pbonzini@...hat.com,
	seanjc@...gle.com, vannapurve@...gle.com,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	H Peter Anvin <hpa@...or.com>, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	rick.p.edgecombe@...el.com, kai.huang@...el.com,
	reinette.chatre@...el.com, xiaoyao.li@...el.com,
	tony.lindgren@...ux.intel.com, binbin.wu@...ux.intel.com,
	ira.weiny@...el.com, isaku.yamahata@...el.com,
	Fan Du <fan.du@...el.com>, Yazen Ghannam <yazen.ghannam@....com>,
	yan.y.zhao@...el.com, chao.gao@...el.com
Subject: Re: [PATCH RESEND V2 1/2] x86/mce: Fix missing address mask in
 recovery for errors in TDX/SEAM non-root mode

On Tue, Aug 19, 2025 at 07:24:34PM +0300, Adrian Hunter wrote:
> Commit 8a01ec97dc066 ("x86/mce: Mask out non-address bits from machine
> check bank") introduced a new #define MCI_ADDR_PHYSADDR for the mask of
> valid physical address bits within the machine check bank address register.
> 
> This is particularly needed in the case of errors in TDX/SEAM non-root mode
> because the reported address contains the TDX KeyID.  Refer to TDX and
> TME-MK documentation for more information about KeyIDs.
> 
> Commit 7911f145de5fe ("x86/mce: Implement recovery for errors in TDX/SEAM
> non-root mode") uses the address to mark the affected page as poisoned, but
> omits to use the aforementioned mask.
> 
> Investigation of user space expectations has concluded it would be more
> correct for the address to contain only address bits in the first place.
> Refer https://lore.kernel.org/r/807ff02d-7af0-419d-8d14-a4d6c5d5420d@intel.com
> 
> Mask the address when it is read from the machine check bank address
> register.  Do not use MCI_ADDR_PHYSADDR because that will be removed in a
> later patch.

Why is this patch talking about TDX-something but doing "global" changes to
mce.addr?

Why don't you simply do a TDX-specific masking out when you're running on
in TDX env and leave the rest as is?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette