On Wed, Nov 06, 2024, Mario Limonciello wrote: > On 11/6/2024 09:03, Sean Christopherson wrote: > > +KVM, given that this quite obviously affects KVM... > > > > On Tue, Nov 05, 2024, Mario Limonciello wrote: > > > From: Mario Limonciello <mario.limonciello@xxxxxxx> > > > > > > A number of Zen4 client SoCs advertise the ability to use virtualized > > > VMLOAD/VMSAVE, but using these instructions is reported to be a cause > > > of a random host reboot. > > > > > > These instructions aren't intended to be advertised on Zen4 client > > > so clear the capability. > > > > > > Cc: stable@xxxxxxxxxxxxxxx > > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=219009 > > > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx> > > > --- > > > arch/x86/kernel/cpu/amd.c | 11 +++++++++++ > > > 1 file changed, 11 insertions(+) > > > > > > diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c > > > index 015971adadfc7..ecd42c2b3242e 100644 > > > --- a/arch/x86/kernel/cpu/amd.c > > > +++ b/arch/x86/kernel/cpu/amd.c > > > @@ -924,6 +924,17 @@ static void init_amd_zen4(struct cpuinfo_x86 *c) > > > { > > > if (!cpu_has(c, X86_FEATURE_HYPERVISOR)) > > > msr_set_bit(MSR_ZEN4_BP_CFG, MSR_ZEN4_BP_CFG_SHARED_BTB_FIX_BIT); > > > + > > > + /* > > > + * These Zen4 SoCs advertise support for virtualized VMLOAD/VMSAVE > > > + * in some BIOS versions but they can lead to random host reboots. > > > > Uh, CPU bug? Erratum? > > BIOS bug. Those shouldn't have been advertised. Why not? "but they can lead to random host reboots" is a description of the symptom, not an explanation for why KVM is unable to use a feature that is apparently support by the CPU. And if the CPU doesn't actually support virtualized VMLOAD/VMSAVE, then this is a much bigger problem, because it means KVM is effectively giving the guest read and write access to all of host memory.
