From patchwork Fri Jun 14 09:58:51 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Kirill A. 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Shutemov" To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "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 , "H. Peter Anvin" , "Kirill A. Shutemov" , "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 Subject: [PATCHv12 06/19] x86/kexec: Keep CR4.MCE set during kexec for TDX guest Date: Fri, 14 Jun 2024 12:58:51 +0300 Message-ID: <20240614095904.1345461-7-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240614095904.1345461-1-kirill.shutemov@linux.intel.com> References: <20240614095904.1345461-1-kirill.shutemov@linux.intel.com> Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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. 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 8b8922de3765..042c9a0334e9 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 /* Flush the TLB (needed?) */ movq %r9, %cr3