[PATCH v5 08/19] KVM:x86: Report KVM supported CET MSRs as to-be-saved

Yang Weijiang
2023-08-03T07:37:29Z

Add all CET MSRs including the synthesized GUEST_SSP to report list.
PL{0,1,2}_SSP are independent to host XSAVE management with later
patches. MSR_IA32_U_CET and MSR_IA32_PL3_SSP are XSAVE-managed on
host side. MSR_IA32_S_CET/MSR_IA32_INT_SSP_TAB/MSR_KVM_GUEST_SSP
are not XSAVE-managed.

When CET IBT/SHSTK are enumerated to guest, both user and supervisor
modes should be supported for architechtural integrity, i.e., two
modes are supported as both or neither.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/include/uapi/asm/kvm_para.h | 1 +
arch/x86/kvm/x86.c | 10 ++++++++++
arch/x86/kvm/x86.h | 10 ++++++++++
3 files changed, 21 insertions(+)

diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 6e64b27b2c1e..7af465e4e0bd 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -58,6 +58,7 @@
#define MSR_KVM_ASYNC_PF_INT 0x4b564d06
#define MSR_KVM_ASYNC_PF_ACK 0x4b564d07
#define MSR_KVM_MIGRATION_CONTROL 0x4b564d08
+#define MSR_KVM_GUEST_SSP 0x4b564d09

struct kvm_steal_time {
__u64 steal;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 82b9f14990da..d68ef87fe007 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1463,6 +1463,9 @@ static const u32 msrs_to_save_base[] = {

MSR_IA32_XFD, MSR_IA32_XFD_ERR,
MSR_IA32_XSS,
+ MSR_IA32_U_CET, MSR_IA32_S_CET,
+ MSR_IA32_PL0_SSP, MSR_IA32_PL1_SSP, MSR_IA32_PL2_SSP,
+ MSR_IA32_PL3_SSP, MSR_IA32_INT_SSP_TAB, MSR_KVM_GUEST_SSP,
};

static const u32 msrs_to_save_pmu[] = {
@@ -7214,6 +7217,13 @@ static void kvm_probe_msr_to_save(u32 msr_index)
if (!kvm_caps.supported_xss)
return;
break;
+ case MSR_IA32_U_CET:
+ case MSR_IA32_S_CET:
+ case MSR_KVM_GUEST_SSP:
+ case MSR_IA32_PL0_SSP ... MSR_IA32_INT_SSP_TAB:
+ if (!kvm_is_cet_supported())
+ return;
+ break;
default:
break;
}
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 82e3dafc5453..6e6292915f8c 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -362,6 +362,16 @@ static inline bool kvm_mpx_supported(void)
== (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR);
}

+#define CET_XSTATE_MASK (XFEATURE_MASK_CET_USER)
+/*
+ * Shadow Stack and Indirect Branch Tracking feature enabling depends on
+ * whether host side CET user xstate bit is supported or not.
+ */
+static inline bool kvm_is_cet_supported(void)
+{
+ return (kvm_caps.supported_xss & CET_XSTATE_MASK) == CET_XSTATE_MASK;
+}
+
extern unsigned int min_timer_period_us;

extern bool enable_vmware_backdoor;
--
2.27.0