linux-kernel - Re: [PATCHv11 06/19] x86/kexec: Keep CR4.MCE set during kexec for TDX guest

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Date: Wed, 29 May 2024 14:39:33 +0300
From: Nikolay Borisov <nik.borisov@...e.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
 Elena Reshetova <elena.reshetova@...el.com>,
 Jun Nakajima <jun.nakajima@...el.com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Tom Lendacky <thomas.lendacky@....com>, "Kalra, Ashish"
 <ashish.kalra@....com>, Sean Christopherson <seanjc@...gle.com>,
 "Huang, Kai" <kai.huang@...el.com>, Ard Biesheuvel <ardb@...nel.org>,
 Baoquan He <bhe@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
 "K. Y. Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, kexec@...ts.infradead.org,
 linux-hyperv@...r.kernel.org, linux-acpi@...r.kernel.org,
 linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv11 06/19] x86/kexec: Keep CR4.MCE set during kexec for TDX
 guest

On 28.05.24 г. 12:55 ч., Kirill A. Shutemov wrote:
> TDX guests run with MCA enabled (CR4.MCE=1b) from the very start. If
> that bit is cleared during CR4 register reprogramming during boot or
> kexec flows, a #VE exception will be raised which the guest kernel
> cannot handle it.
> 
> Therefore, make sure the CR4.MCE setting is preserved over kexec too and
> avoid raising any #VEs.
> 
> The change doesn't affect non-TDX-guest environments.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>