linux-kernel - Re: [PATCH v2] x86/kexec: Add EFI config table identity mapping for kexec kernel

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Message-ID: <20230713100459.GEZK/MS69XbphJa+tN@fat_crate.local>
Date:   Thu, 13 Jul 2023 12:04:59 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tao Liu <ltao@...hat.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, ardb@...nel.org,
        linux-kernel@...r.kernel.org, bhe@...hat.com, dyoung@...hat.com,
        kexec@...ts.infradead.org, linux-efi@...r.kernel.org
Subject: Re: [PATCH v2] x86/kexec: Add EFI config table identity mapping for
 kexec kernel

On Thu, Jun 01, 2023 at 03:20:44PM +0800, Tao Liu wrote:
>  arch/x86/kernel/machine_kexec_64.c | 35 ++++++++++++++++++++++++++----
>  1 file changed, 31 insertions(+), 4 deletions(-)

Ok, pls try this totally untested thing.

Thx.

---
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 09dc8c187b3c..fefe27b2af85 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -404,13 +404,20 @@ void sev_enable(struct boot_params *bp)
 	if (bp)
 		bp->cc_blob_address = 0;
 
+	/* Check for the SME/SEV support leaf */
+	eax = 0x80000000;
+	ecx = 0;
+	native_cpuid(&eax, &ebx, &ecx, &edx);
+	if (eax < 0x8000001f)
+		return;
+
 	/*
 	 * Setup/preliminary detection of SNP. This will be sanity-checked
 	 * against CPUID/MSR values later.
 	 */
 	snp = snp_init(bp);
 
-	/* Check for the SME/SEV support leaf */
+	/* Recheck the SME/SEV support leaf */
 	eax = 0x80000000;
 	ecx = 0;
 	native_cpuid(&eax, &ebx, &ecx, &edx);


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette