SPDX-FileCopyrightText: 2022 Sean Christopherson <seanjc@google.com>
SPDX-License-Identifier: GPL-2.0-only
Revert the following patch:
From ddfd117714014cebe7b5d008fdec8eaec620cba1 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Wed, 30 Nov 2022 23:36:48 +0000
Subject: [PATCH] x86/virt: Force GIF=1 prior to disabling SVM (for reboot
flows)
commit 6a3236580b0b1accc3976345e723104f74f6f8e6 upstream.
Set GIF=1 prior to disabling SVM to ensure that INIT is recognized if the
kernel is disabling SVM in an emergency, e.g. if the kernel is about to
jump into a crash kernel or may reboot without doing a full CPU RESET.
If GIF is left cleared, the new kernel (or firmware) will be unabled to
awaken APs. Eat faults on STGI (due to EFER.SVME=0) as it's possible
that SVM could be disabled via NMI shootdown between reading EFER.SVME
and executing STGI.
Link: https://lore.kernel.org/all/cbcb6f35-e5d7-c1c9-4db9-fe5cc4de579a@amd.com
Cc: stable@vger.kernel.org
Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20221130233650.1404148-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/include/asm/virtext.h | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h
index 0116b2ee9e64f..4699acd602af4 100644
--- linux-4.14.336/arch/x86/include/asm/virtext.h
+++ linux-4.14.336/arch/x86/include/asm/virtext.h
@@ -114,21 +114,7 @@ static inline void cpu_svm_disable(void)
wrmsrl(MSR_VM_HSAVE_PA, 0);
rdmsrl(MSR_EFER, efer);
- if (efer & EFER_SVME) {
- /*
- * Force GIF=1 prior to disabling SVM to ensure INIT and NMI
- * aren't blocked, e.g. if a fatal error occurred between CLGI
- * and STGI. Note, STGI may #UD if SVM is disabled from NMI
- * context between reading EFER and executing STGI. In that
- * case, GIF must already be set, otherwise the NMI would have
- * been blocked, so just eat the fault.
- */
- asm_volatile_goto("1: stgi\n\t"
- _ASM_EXTABLE(1b, %l[fault])
- ::: "memory" : fault);
-fault:
- wrmsrl(MSR_EFER, efer & ~EFER_SVME);
- }
+ wrmsrl(MSR_EFER, efer & ~EFER_SVME);
}
/** Makes sure SVM is disabled, if it is supported on the CPU