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From:   Thomas Gleixner <tglx@linutronix.de>
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
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Subject: [patch] x86/smpboot: Disable parallel bootup if cc_vendor != NONE
In-Reply-To: <87jzwqjeey.ffs@tglx>
References: <20230508181633.089804905@linutronix.de>
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Date:   Tue, 30 May 2023 14:09:17 +0200
Message-ID: <87cz2ija1e.ffs@tglx>
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The decision to allow parallel bringup of secondary CPUs checks
CC_ATTR_GUEST_STATE_ENCRYPT to detect encrypted guests. Those cannot use
parallel bootup because accessing the local APIC is intercepted and raises
a #VC or #VE, which cannot be handled at that point.

The check works correctly, but only for AMD encrypted guests. TDX does not
set that flag.

Check for cc_vendor != CC_VENDOR_NONE instead. That might be overbroad, but
definitely works for both AMD and Intel.

Fixes: 0c7ffa32dbd6 ("x86/smpboot/64: Implement arch_cpuhp_init_parallel_bringup() and enable it")
Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/smpboot.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1282,7 +1282,7 @@ bool __init arch_cpuhp_init_parallel_bri
 	 * Intel-TDX has a secure RDMSR hypercall, but that needs to be
 	 * implemented seperately in the low level startup ASM code.
 	 */
-	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) {
+	if (cc_get_vendor() != CC_VENDOR_NONE) {
 		pr_info("Parallel CPU startup disabled due to guest state encryption\n");
 		return false;
 	}