[PATCH 6.7 04/61] KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests

Sasha Levin
2024-03-13T16:32:44Z

From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>

commit 2a0180129d726a4b953232175857d442651b55a0 upstream.

Mitigation for RFDS requires RFDS_CLEAR capability which is enumerated
by MSR_IA32_ARCH_CAPABILITIES bit 27. If the host has it set, export it
to guests so that they can deploy the mitigation.

RFDS_NO indicates that the system is not vulnerable to RFDS, export it
to guests so that they don't deploy the mitigation unnecessarily. When
the host is not affected by X86_BUG_RFDS, but has RFDS_NO=0, synthesize
RFDS_NO to the guest.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/x86.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 468870450b8ba..8021c62b0e7b0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1620,7 +1620,8 @@ static bool kvm_is_immutable_feature_msr(u32 msr)
ARCH_CAP_SKIP_VMENTRY_L1DFLUSH | ARCH_CAP_SSB_NO | ARCH_CAP_MDS_NO | \
ARCH_CAP_PSCHANGE_MC_NO | ARCH_CAP_TSX_CTRL_MSR | ARCH_CAP_TAA_NO | \
ARCH_CAP_SBDR_SSDP_NO | ARCH_CAP_FBSDP_NO | ARCH_CAP_PSDP_NO | \
- ARCH_CAP_FB_CLEAR | ARCH_CAP_RRSBA | ARCH_CAP_PBRSB_NO | ARCH_CAP_GDS_NO)
+ ARCH_CAP_FB_CLEAR | ARCH_CAP_RRSBA | ARCH_CAP_PBRSB_NO | ARCH_CAP_GDS_NO | \
+ ARCH_CAP_RFDS_NO | ARCH_CAP_RFDS_CLEAR)

static u64 kvm_get_arch_capabilities(void)
{
@@ -1652,6 +1653,8 @@ static u64 kvm_get_arch_capabilities(void)
data |= ARCH_CAP_SSB_NO;
if (!boot_cpu_has_bug(X86_BUG_MDS))
data |= ARCH_CAP_MDS_NO;
+ if (!boot_cpu_has_bug(X86_BUG_RFDS))
+ data |= ARCH_CAP_RFDS_NO;

if (!boot_cpu_has(X86_FEATURE_RTM)) {
/*
--
2.43.0