Handle host initiated FRED MSR access requests to allow FRED context
to be set/get from user level.
During VM save/restore and live migration, FRED context needs to be
saved/restored, which requires FRED MSRs to be accessed from a user
level application, e.g., Qemu.
Note, handling of MSR_IA32_FRED_SSP0, i.e., MSR_IA32_PL0_SSP, is not
added yet, which is done in the KVM CET patch set.
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
---
Changes since v1:
* Use kvm_cpu_cap_has() instead of cpu_feature_enabled() (Chao Gao).
* Fail host requested FRED MSRs access if KVM cannot virtualize FRED
(Chao Gao).
* Handle the case FRED MSRs are valid but KVM cannot virtualize FRED
(Chao Gao).
* Add sanity checks when writing to FRED MSRs.
---
arch/x86/kvm/vmx/vmx.c | 72 ++++++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 47 +++++++++++++++++++++++++++
2 files changed, 119 insertions(+)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 264378c3b784..ee61d2c25cb0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1420,6 +1420,24 @@ static void vmx_write_guest_kernel_gs_base(struct vcpu_vmx *vmx, u64 data)
preempt_enable();
vmx->msr_guest_kernel_gs_base = data;
}
+
+static u64 vmx_read_guest_fred_rsp0(struct vcpu_vmx *vmx)
+{
+ preempt_disable();
+ if (vmx->guest_state_loaded)
+ vmx->msr_guest_fred_rsp0 = read_msr(MSR_IA32_FRED_RSP0);
+ preempt_enable();
+ return vmx->msr_guest_fred_rsp0;
+}
+
+static void vmx_write_guest_fred_rsp0(struct vcpu_vmx *vmx, u64 data)
+{
+ preempt_disable();
+ if (vmx->guest_state_loaded)
+ wrmsrl(MSR_IA32_FRED_RSP0, data);
+ preempt_enable();
+ vmx->msr_guest_fred_rsp0 = data;
+}
#endif
void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu,
@@ -2019,6 +2037,33 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_KERNEL_GS_BASE:
msr_info->data = vmx_read_guest_kernel_gs_base(vmx);
break;
+ case MSR_IA32_FRED_RSP0:
+ msr_info->data = vmx_read_guest_fred_rsp0(vmx);
+ break;
+ case MSR_IA32_FRED_RSP1:
+ msr_info->data = vmcs_read64(GUEST_IA32_FRED_RSP1);
+ break;
+ case MSR_IA32_FRED_RSP2:
+ msr_info->data = vmcs_read64(GUEST_IA32_FRED_RSP2);
+ break;
+ case MSR_IA32_FRED_RSP3:
+ msr_info->data = vmcs_read64(GUEST_IA32_FRED_RSP3);
+ break;
+ case MSR_IA32_FRED_STKLVLS:
+ msr_info->data = vmcs_read64(GUEST_IA32_FRED_STKLVLS);
+ break;
+ case MSR_IA32_FRED_SSP1:
+ msr_info->data = vmcs_read64(GUEST_IA32_FRED_SSP1);
+ break;
+ case MSR_IA32_FRED_SSP2:
+ msr_info->data = vmcs_read64(GUEST_IA32_FRED_SSP2);
+ break;
+ case MSR_IA32_FRED_SSP3:
+ msr_info->data = vmcs_read64(GUEST_IA32_FRED_SSP3);
+ break;
+ case MSR_IA32_FRED_CONFIG:
+ msr_info->data = vmcs_read64(GUEST_IA32_FRED_CONFIG);
+ break;
#endif
case MSR_EFER:
return kvm_get_msr_common(vcpu, msr_info);
@@ -2226,6 +2271,33 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
vmx_update_exception_bitmap(vcpu);
}
break;
+ case MSR_IA32_FRED_RSP0:
+ vmx_write_guest_fred_rsp0(vmx, data);
+ break;
+ case MSR_IA32_FRED_RSP1:
+ vmcs_write64(GUEST_IA32_FRED_RSP1, data);
+ break;
+ case MSR_IA32_FRED_RSP2:
+ vmcs_write64(GUEST_IA32_FRED_RSP2, data);
+ break;
+ case MSR_IA32_FRED_RSP3:
+ vmcs_write64(GUEST_IA32_FRED_RSP3, data);
+ break;
+ case MSR_IA32_FRED_STKLVLS:
+ vmcs_write64(GUEST_IA32_FRED_STKLVLS, data);
+ break;
+ case MSR_IA32_FRED_SSP1:
+ vmcs_write64(GUEST_IA32_FRED_SSP1, data);
+ break;
+ case MSR_IA32_FRED_SSP2:
+ vmcs_write64(GUEST_IA32_FRED_SSP2, data);
+ break;
+ case MSR_IA32_FRED_SSP3:
+ vmcs_write64(GUEST_IA32_FRED_SSP3, data);
+ break;
+ case MSR_IA32_FRED_CONFIG:
+ vmcs_write64(GUEST_IA32_FRED_CONFIG, data);
+ break;
#endif
case MSR_IA32_SYSENTER_CS:
if (is_guest_mode(vcpu))
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 363b1c080205..4e8d60f248e3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1451,6 +1451,9 @@ static const u32 msrs_to_save_base[] = {
MSR_STAR,
#ifdef CONFIG_X86_64
MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
+ MSR_IA32_FRED_RSP0, MSR_IA32_FRED_RSP1, MSR_IA32_FRED_RSP2,
+ MSR_IA32_FRED_RSP3, MSR_IA32_FRED_STKLVLS, MSR_IA32_FRED_SSP1,
+ MSR_IA32_FRED_SSP2, MSR_IA32_FRED_SSP3, MSR_IA32_FRED_CONFIG,
#endif
MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
MSR_IA32_FEAT_CTL, MSR_IA32_BNDCFGS, MSR_TSC_AUX,
@@ -1892,6 +1895,30 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data,
return 1;
data = (u32)data;
+ break;
+ case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG:
+ if (index != MSR_IA32_FRED_STKLVLS && is_noncanonical_address(data, vcpu))
+ return 1;
+ if ((index >= MSR_IA32_FRED_RSP0 && index <= MSR_IA32_FRED_RSP3) &&
+ (data & GENMASK_ULL(5, 0)))
+ return 1;
+ if ((index >= MSR_IA32_FRED_SSP1 && index <= MSR_IA32_FRED_SSP3) &&
+ (data & GENMASK_ULL(2, 0)))
+ return 1;
+
+ if (host_initiated) {
+ if (!kvm_cpu_cap_has(X86_FEATURE_FRED))
+ return 1;
+ } else {
+ /*
+ * Inject #GP upon FRED MSRs accesses from a non-FRED guest,
+ * which also ensures no malicious guest can write to FRED
+ * MSRs to corrupt host FRED MSRs.
+ */
+ if (!guest_can_use(vcpu, X86_FEATURE_FRED))
+ return 1;
+ }
+
break;
}
@@ -1936,6 +1963,22 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data,
!guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
return 1;
break;
+ case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG:
+ if (host_initiated) {
+ if (!kvm_cpu_cap_has(X86_FEATURE_FRED))
+ return 1;
+ } else {
+ /*
+ * Inject #GP upon FRED MSRs accesses from a non-FRED guest,
+ * which also ensures no malicious guest can write to FRED
+ * MSRs to corrupt host FRED MSRs.
+ */
+ if (!guest_can_use(vcpu, X86_FEATURE_FRED))
+ return 1;
+ }
+
+ break;
+
}
msr.index = index;
@@ -7364,6 +7407,10 @@ static void kvm_probe_msr_to_save(u32 msr_index)
if (!(kvm_get_arch_capabilities() & ARCH_CAP_TSX_CTRL_MSR))
return;
break;
+ case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG:
+ if (!kvm_cpu_cap_has(X86_FEATURE_FRED))
+ return;
+ break;
default:
break;
}
--
2.43.0
