diff options
| author | Sean Christopherson | 2022-11-30 23:36:48 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2023-03-10 09:34:13 +0100 |
| commit | c4765c973c1d83964cea75881d83040cfa4109da (patch) | |
| tree | a679569954b828a99ac41a747e4e86a08bc220f6 | |
| parent | b261024d7ea8aebfd1ac4a36d5d1ae0a62f1a97e (diff) | |
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>
| -rw-r--r-- | arch/x86/include/asm/virtext.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h index 8757078d4442..3b12e6b99412 100644 --- a/arch/x86/include/asm/virtext.h +++ b/arch/x86/include/asm/virtext.h @@ -126,7 +126,21 @@ 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 |