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: <a000ac49-a671-49ff-8c5c-aa82930ff20c@intel.com>
Date: Thu, 21 Aug 2025 09:49:07 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Yazen Ghannam <yazen.ghannam@....com>, "Luck, Tony" <tony.luck@...el.com>
CC: Dave Hansen <dave.hansen@...ux.intel.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "seanjc@...gle.com" <seanjc@...gle.com>, "Annapurve,
 Vishal" <vannapurve@...gle.com>, Borislav Petkov <bp@...en8.de>, "Thomas
 Gleixner" <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.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>, "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>, "Weiny, Ira"
	<ira.weiny@...el.com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>, "Du,
 Fan" <fan.du@...el.com>, "Zhao, Yan Y" <yan.y.zhao@...el.com>, "Gao, Chao"
	<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 20/08/2025 20:56, Yazen Ghannam wrote:
> On Wed, Aug 20, 2025 at 04:12:28PM +0000, Luck, Tony wrote:
>>>>> For struct mce?  Maybe that should be 2 new fields:
>>>>>
>>>>>    __u64 addr;             /* Deprecated */
>>>>>    ...
>>>>>    __u64 mci_addr;         /* Bank's MCi_ADDR MSR */
>>>>>    __u64 phys_addr;        /* Physical address */
>>>>
>>>> Would "addr" keep the current (low bits masked, high bits preserved) value?
>>>
>>> Yeah, it wouldn't make much sense if phys_addr was the same as addr anyway.
>>> Not really thinking
>>
>> The other option (but a bad one) would be:
>>
>>         __u64 deprecated;       /* was "addr" */
>>         ...
>>         __u64 mci_addr;         /* Bank's MCi_ADDR MSR */
>>         __u64 phys_addr;        /* Physical address */
>>
>> which would be good to force cleanup in the kernel, but bad for preserving
>> ABI (since "struct mce" is visible to user space via /dev/mcelog).
>>
> 
> /dev/mcelog has been deprecated for a while.

There is also mce_record tracepoint

> 
> Is the mcelog app still in active development? Could it be updated to
> use trace events for MCE info?
> 
> You could also just fix up the address value in the mcelog notifier's
> copy. I believe it has its own cache separate from the MCE genpool.

Is there an advantage to fixing up later rather than when addr is
initially assigned?