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Shutemov" Cc: Sean Christopherson , Thomas Gleixner , Ingo Molnar , Dave Hansen , x86@kernel.org, "Rafael J. Wysocki" , Peter Zijlstra , Adrian Hunter , Kuppuswamy Sathyanarayanan , Elena Reshetova , Jun Nakajima , Rick Edgecombe , Tom Lendacky , Ashish Kalra , Kai Huang , Baoquan He , kexec@lists.infradead.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCHv10 05/18] x86/kexec: Keep CR4.MCE set during kexec for TDX guest Message-ID: <20240430125744.GQZjDqyM3k_peEw-bc@fat_crate.local> References: <20240409113010.465412-1-kirill.shutemov@linux.intel.com> <20240409113010.465412-6-kirill.shutemov@linux.intel.com> <3q6jv3g4tezybmd667mqxio7ty22akxv7okrznmzx3tju2u4qo@2alzjkbgm2lh> <20240428171111.GKZi6DLy_ZwuZsZdFq@fat_crate.local> <20240429144454.GHZi-yZkD0boKk5N17@fat_crate.local> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Mon, Apr 29, 2024 at 06:16:54PM +0300, Kirill A. Shutemov wrote: > Yes, that's what happens in current upstream. Let's rewrite that commit message then: "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 that early. Therefore, make sure the CR4.MCE setting is preserved over kexec too and avoid raising any #VEs." without that bit about TDX guests might be allowed to clear CR4.MCE which is only confusing and unnecessary. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette