KVM: x86: Propagate AMD's IbrsSameMode to the guest

If IBRS provides same mode (kernel/user or host/guest) protection on the
host, then by definition it also provides same mode protection in the
guest. In fact, all different modes from the guest's perspective are the
same mode from the host's perspective anyway.

Propagate IbrsSameMode to the guests.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Reviewed-by: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20250221163352.3818347-3-yosry.ahmed@linux.dev
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e92263fbbad681db0859bc7bb3ce5be7e29d6bff..f678cbda6ebf5a008446db83bba42cb662342e86 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1093,6 +1093,7 @@ void kvm_set_cpu_caps(void)
                F(AMD_SSB_NO),
                F(AMD_STIBP),
                F(AMD_STIBP_ALWAYS_ON),
+               F(AMD_IBRS_SAME_MODE),
                F(AMD_PSFD),
                F(AMD_IBPB_RET),
        );