linux-kernel - RE: [PATCH v7] x86/mce: retrieve poison range from hardware

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Message-ID: <SJ1PR11MB6083C23BE7762FAC64717FABFC709@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Tue, 23 Aug 2022 16:58:05 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>, "chu, jane" <jane.chu@...cle.com>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch@....de" <hch@....de>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>
Subject: RE: [PATCH v7] x86/mce: retrieve poison range from hardware

> What I'm missing from this text here is, what *is* the mce->misc LSB
> field in human speak? What does that field denote?

The SDM says:

 Recoverable Address LSB (bits 5:0): The lowest valid recoverable address bit. Indicates the position of the least
 significant bit (LSB) of the recoverable error address. For example, if the processor logs bits [43:9] of the
 address, the LSB sub-field in IA32_MCi_MISC is 01001b (9 decimal). For this example, bits [8:0] of the
 recoverable error address in IA32_MCi_ADDR should be ignored.

So in human speak "how much data did you lose". "6" is a common value saying a cache line (2<<6 == 64)
was lost. Sometimes you see "12' (2<<12 == 4096) for a whole page lost.

-Tony