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[92.26.98.202]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-422f641a64bsm2618385e9.46.2024.06.12.16.06.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Jun 2024 16:06:08 -0700 (PDT) Message-ID: Date: Thu, 13 Jun 2024 00:06:07 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv11 05/19] x86/relocate_kernel: Use named labels for less confusion To: "Kirill A. Shutemov" , "H. Peter Anvin" Cc: Borislav Petkov , Nikolay Borisov , 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 , "Kalra, Ashish" , Sean Christopherson , "Huang, Kai" , Ard Biesheuvel , Baoquan He , "K. Y. Srinivasan" , Haiyang Zhang , kexec@lists.infradead.org, linux-hyperv@vger.kernel.org, linux-acpi@vger.kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org References: <20240528095522.509667-1-kirill.shutemov@linux.intel.com> <20240528095522.509667-6-kirill.shutemov@linux.intel.com> <1e1d1aea-7346-4022-9f5f-402d171adfda@suse.com> <748d3b70-60b4-44e0-bd81-9117f1ab699d@zytor.com> <20240604091503.GQZl7bF14qTSAjqUhN@fat_crate.local> <5c8b3ee9-64c2-4ff3-9cca-ba2672b9635e@zytor.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; keydata= xsFNBFLhNn8BEADVhE+Hb8i0GV6mihnnr/uiQQdPF8kUoFzCOPXkf7jQ5sLYeJa0cQi6Penp VtiFYznTairnVsN5J+ujSTIb+OlMSJUWV4opS7WVNnxHbFTPYZVQ3erv7NKc2iVizCRZ2Kxn srM1oPXWRic8BIAdYOKOloF2300SL/bIpeD+x7h3w9B/qez7nOin5NzkxgFoaUeIal12pXSR Q354FKFoy6Vh96gc4VRqte3jw8mPuJQpfws+Pb+swvSf/i1q1+1I4jsRQQh2m6OTADHIqg2E ofTYAEh7R5HfPx0EXoEDMdRjOeKn8+vvkAwhviWXTHlG3R1QkbE5M/oywnZ83udJmi+lxjJ5 YhQ5IzomvJ16H0Bq+TLyVLO/VRksp1VR9HxCzItLNCS8PdpYYz5TC204ViycobYU65WMpzWe LFAGn8jSS25XIpqv0Y9k87dLbctKKA14Ifw2kq5OIVu2FuX+3i446JOa2vpCI9GcjCzi3oHV e00bzYiHMIl0FICrNJU0Kjho8pdo0m2uxkn6SYEpogAy9pnatUlO+erL4LqFUO7GXSdBRbw5 gNt25XTLdSFuZtMxkY3tq8MFss5QnjhehCVPEpE6y9ZjI4XB8ad1G4oBHVGK5LMsvg22PfMJ ISWFSHoF/B5+lHkCKWkFxZ0gZn33ju5n6/FOdEx4B8cMJt+cWwARAQABzSlBbmRyZXcgQ29v cGVyIDxhbmRyZXcuY29vcGVyM0BjaXRyaXguY29tPsLBegQTAQgAJAIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUCWKD95wIZAQAKCRBlw/kGpdefoHbdD/9AIoR3k6fKl+RFiFpyAhvO 59ttDFI7nIAnlYngev2XUR3acFElJATHSDO0ju+hqWqAb8kVijXLops0gOfqt3VPZq9cuHlh IMDquatGLzAadfFx2eQYIYT+FYuMoPZy/aTUazmJIDVxP7L383grjIkn+7tAv+qeDfE+txL4 SAm1UHNvmdfgL2/lcmL3xRh7sub3nJilM93RWX1Pe5LBSDXO45uzCGEdst6uSlzYR/MEr+5Z JQQ32JV64zwvf/aKaagSQSQMYNX9JFgfZ3TKWC1KJQbX5ssoX/5hNLqxMcZV3TN7kU8I3kjK mPec9+1nECOjjJSO/h4P0sBZyIUGfguwzhEeGf4sMCuSEM4xjCnwiBwftR17sr0spYcOpqET ZGcAmyYcNjy6CYadNCnfR40vhhWuCfNCBzWnUW0lFoo12wb0YnzoOLjvfD6OL3JjIUJNOmJy RCsJ5IA/Iz33RhSVRmROu+TztwuThClw63g7+hoyewv7BemKyuU6FTVhjjW+XUWmS/FzknSi dAG+insr0746cTPpSkGl3KAXeWDGJzve7/SBBfyznWCMGaf8E2P1oOdIZRxHgWj0zNr1+ooF /PzgLPiCI4OMUttTlEKChgbUTQ+5o0P080JojqfXwbPAyumbaYcQNiH1/xYbJdOFSiBv9rpt TQTBLzDKXok86M7BTQRS4TZ/ARAAkgqudHsp+hd82UVkvgnlqZjzz2vyrYfz7bkPtXaGb9H4 Rfo7mQsEQavEBdWWjbga6eMnDqtu+FC+qeTGYebToxEyp2lKDSoAsvt8w82tIlP/EbmRbDVn 7bhjBlfRcFjVYw8uVDPptT0TV47vpoCVkTwcyb6OltJrvg/QzV9f07DJswuda1JH3/qvYu0p vjPnYvCq4NsqY2XSdAJ02HrdYPFtNyPEntu1n1KK+gJrstjtw7KsZ4ygXYrsm/oCBiVW/OgU g/XIlGErkrxe4vQvJyVwg6YH653YTX5hLLUEL1NS4TCo47RP+wi6y+TnuAL36UtK/uFyEuPy wwrDVcC4cIFhYSfsO0BumEI65yu7a8aHbGfq2lW251UcoU48Z27ZUUZd2Dr6O/n8poQHbaTd 6bJJSjzGGHZVbRP9UQ3lkmkmc0+XCHmj5WhwNNYjgbbmML7y0fsJT5RgvefAIFfHBg7fTY/i kBEimoUsTEQz+N4hbKwo1hULfVxDJStE4sbPhjbsPCrlXf6W9CxSyQ0qmZ2bXsLQYRj2xqd1 bpA+1o1j2N4/au1R/uSiUFjewJdT/LX1EklKDcQwpk06Af/N7VZtSfEJeRV04unbsKVXWZAk uAJyDDKN99ziC0Wz5kcPyVD1HNf8bgaqGDzrv3TfYjwqayRFcMf7xJaL9xXedMcAEQEAAcLB XwQYAQgACQUCUuE2fwIbDAAKCRBlw/kGpdefoG4XEACD1Qf/er8EA7g23HMxYWd3FXHThrVQ HgiGdk5Yh632vjOm9L4sd/GCEACVQKjsu98e8o3ysitFlznEns5EAAXEbITrgKWXDDUWGYxd pnjj2u+GkVdsOAGk0kxczX6s+VRBhpbBI2PWnOsRJgU2n10PZ3mZD4Xu9kU2IXYmuW+e5KCA vTArRUdCrAtIa1k01sPipPPw6dfxx2e5asy21YOytzxuWFfJTGnVxZZSCyLUO83sh6OZhJkk b9rxL9wPmpN/t2IPaEKoAc0FTQZS36wAMOXkBh24PQ9gaLJvfPKpNzGD8XWR5HHF0NLIJhgg 4ZlEXQ2fVp3XrtocHqhu4UZR4koCijgB8sB7Tb0GCpwK+C4UePdFLfhKyRdSXuvY3AHJd4CP 4JzW0Bzq/WXY3XMOzUTYApGQpnUpdOmuQSfpV9MQO+/jo7r6yPbxT7CwRS5dcQPzUiuHLK9i nvjREdh84qycnx0/6dDroYhp0DFv4udxuAvt1h4wGwTPRQZerSm4xaYegEFusyhbZrI0U9tJ B8WrhBLXDiYlyJT6zOV2yZFuW47VrLsjYnHwn27hmxTC/7tvG3euCklmkn9Sl9IAKFu29RSo d5bD8kMSCYsTqtTfT6W4A3qHGvIDta3ptLYpIAOD2sY3GYq2nf3Bbzx81wZK14JdDDHUX2Rs 6+ahAA== In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240612_160614_005589_FDDDE027 X-CRM114-Status: GOOD ( 17.77 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 12/06/2024 10:22 am, Kirill A. Shutemov wrote: > On Tue, Jun 11, 2024 at 11:26:17AM -0700, H. Peter Anvin wrote: >> On 6/4/24 08:21, Kirill A. Shutemov wrote: >>> From b45fe48092abad2612c2bafbb199e4de80c99545 Mon Sep 17 00:00:00 2001 >>> From: "Kirill A. Shutemov" >>> Date: Fri, 10 Feb 2023 12:53:11 +0300 >>> Subject: [PATCHv11.1 06/19] x86/kexec: Keep CR4.MCE set during kexec for TDX guest >>> >>> 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 >>> --- >>> arch/x86/kernel/relocate_kernel_64.S | 17 ++++++++++------- >>> 1 file changed, 10 insertions(+), 7 deletions(-) >>> >>> diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S >>> index 085eef5c3904..9c2cf70c5f54 100644 >>> --- a/arch/x86/kernel/relocate_kernel_64.S >>> +++ b/arch/x86/kernel/relocate_kernel_64.S >>> @@ -5,6 +5,8 @@ >>> */ >>> #include >>> +#include >>> +#include >>> #include >>> #include >>> #include >>> @@ -145,14 +147,15 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) >>> * Set cr4 to a known state: >>> * - physical address extension enabled >>> * - 5-level paging, if it was enabled before >>> + * - Machine check exception on TDX guest, if it was enabled before. >>> + * Clearing MCE might not be allowed in TDX guests, depending on setup. >>> + * >>> + * Use R13 that contains the original CR4 value, read in relocate_kernel(). >>> + * PAE is always set in the original CR4. >>> */ >>> - movl $X86_CR4_PAE, %eax >>> - testq $X86_CR4_LA57, %r13 >>> - jz .Lno_la57 >>> - orl $X86_CR4_LA57, %eax >>> -.Lno_la57: >>> - >>> - movq %rax, %cr4 >>> + andl $(X86_CR4_PAE | X86_CR4_LA57), %r13d >>> + ALTERNATIVE "", __stringify(orl $X86_CR4_MCE, %r13d), X86_FEATURE_TDX_GUEST >>> + movq %r13, %cr4 >> If this is the case, I don't really see a reason to clear MCE per se as I'm >> guessing a machine check here will be fatal anyway? It just changes the >> method of death. > Andrew had a strong opinion on method of death here. > > https://lore.kernel.org/all/1144340e-dd95-ee3b-dabb-579f9a65b3c7@citrix.com Not sure if I intended it to come across that strongly, but given a choice, the !CR4.MCE death is cleaner because at least you're not interpreting garbage and trying to use it as a valid IDT. ~Andrew _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec