linux-kernel - Re: [PATCH v13 04/22] x86/cpu: Detect TDX partial write machine check erratum

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Date:   Mon, 11 Sep 2023 12:39:52 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Raj, Ashok" <ashok.raj@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "nik.borisov@...e.com" <nik.borisov@...e.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v13 04/22] x86/cpu: Detect TDX partial write machine check
 erratum

On Fri, 2023-09-08 at 08:22 -0700, Dave Hansen wrote:
> On 8/25/23 05:14, Kai Huang wrote:
> > TDX memory has integrity and confidentiality protections.  Violations of
> > this integrity protection are supposed to only affect TDX operations and
> > are never supposed to affect the host kernel itself.  In other words,
> > the host kernel should never, itself, see machine checks induced by the
> > TDX integrity hardware.
> 
> This is missing one thing: alluding to how this will be used.  We might
> do that by saying: "To prepare for _____, add ______."
> 
> But that's a minor nit.

Thanks for suggestion.

I thought I somehow mentioned at last in the changelog:

	With this erratum, there are additional things need to be done. 
Similar
	to other CPU bugs, use a CPU bug bit to indicate this erratum ...

Perhaps it's not clear.  How about below?

	With this erratum, there are additional things need to be done around
		kexec() and machine check handler.  To prepare for those changes, add a 		CPU bugbittoindicatethiserratum.Notethisbugreflectsthe		hardwarethusitisdetectedregardlessofwhetherthekernelisbuilt
	with TDX support or not.
> 
> ...
> > Signed-off-by: Kai Huang <kai.huang@...el.com>
> > Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Reviewed-by: David Hildenbrand <david@...hat.com>
> 
> Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>

Thanks!