linux-kernel - Re: [PATCH 1/2] x86/kexec: Preserve CR4.MCE during kexec

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Message-ID: <bcaf4b7121e20ba27dd2cc2b347feb35ae7bfa53.camel@intel.com>
Date:   Thu, 16 Feb 2023 01:49:39 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "Hansen, Dave" <dave.hansen@...el.com>
CC:     "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>
Subject: Re: [PATCH 1/2] x86/kexec: Preserve CR4.MCE during kexec

On Tue, 2023-02-14 at 02:48 +0300, Kirill A. Shutemov wrote:
> TDX guests are not allowed to clear CR4.MCE. Attempt to clear it
> leads
> to #VE.
> 
> Preserve the flag during kexec.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

I wonder whats going on with the pre-existing switching between eax and
rax in this code for the cr0 and cr4 manipulations. Do you know what
the reason is?

Also, for a simple non-tdx kexec regression test:
Tested-by: Rick Edgecombe <rick.p.edgecombe@...el.com>