From ee80fb1dca07f2e222b3c880db5e9bdc66494a95 Mon Sep 17 00:00:00 2001 From: Sean Christopherson 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 Cc: Tom Lendacky Reviewed-by: Thomas Gleixner Link: https://lore.kernel.org/r/20221130233650.1404148-3-seanjc@google.com Signed-off-by: Sean Christopherson Signed-off-by: Greg Kroah-Hartman --- 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 fda3e7747c22..8eefa3386d8c 100644 --- a/arch/x86/include/asm/virtext.h +++ b/arch/x86/include/asm/virtext.h @@ -120,7 +120,21 @@ static inline void cpu_svm_disable(void) wrmsrl(MSR_VM_HSAVE_PA, 0); rdmsrl(MSR_EFER, efer); - wrmsrl(MSR_EFER, efer & ~EFER_SVME); + 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); + } } /** Makes sure SVM is disabled, if it is supported on the CPU