[PATCH v5 6/8] KVM: x86: Add emulation for MSR_IA32_MCx_CTL2 MSRs.

Jue Wang
2022-06-10T17:12:02Z

This patch adds the emulation of IA32_MCi_CTL2 registers to KVM. A
separate mci_ctl2_banks array is used to keep the existing mce_banks
register layout intact.

In Machine Check Architecture, in addition to MCG_CMCI_P, bit 30 of
the per-bank register IA32_MCi_CTL2 controls whether Corrected Machine
Check error reporting is enabled.

Signed-off-by: Jue Wang <juew@google.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/x86.c | 130 ++++++++++++++++++++++----------
2 files changed, 92 insertions(+), 39 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4ff36610af6a..178b7e01bf8f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -806,6 +806,7 @@ struct kvm_vcpu_arch {
u64 mcg_ctl;
u64 mcg_ext_ctl;
u64 *mce_banks;
+ u64 *mci_ctl2_banks;

/* Cache MMIO info */
u64 mmio_gva;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 71d0e2a7b417..b18994907322 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3174,6 +3174,16 @@ static void kvmclock_sync_fn(struct work_struct *work)
KVMCLOCK_SYNC_PERIOD);
}

+/* These helpers are safe iff @msr is known to be an MCx bank MSR. */
+static bool is_mci_control_msr(u32 msr)
+{
+ return (msr & 3) == 0;
+}
+static bool is_mci_status_msr(u32 msr)
+{
+ return (msr & 3) == 1;
+}
+
/*
* On AMD, HWCR[McStatusWrEn] controls whether setting MCi_STATUS results in #GP.
*/
@@ -3192,6 +3202,7 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
unsigned bank_num = mcg_cap & 0xff;
u32 msr = msr_info->index;
u64 data = msr_info->data;
+ u32 offset, last_msr;

switch (msr) {
case MSR_IA32_MCG_STATUS:
@@ -3205,32 +3216,50 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
vcpu->arch.mcg_ctl = data;
break;
- default:
- if (msr >= MSR_IA32_MC0_CTL &&
- msr < MSR_IA32_MCx_CTL(bank_num)) {
- u32 offset = array_index_nospec(
- msr - MSR_IA32_MC0_CTL,
- MSR_IA32_MCx_CTL(bank_num) - MSR_IA32_MC0_CTL);
-
- /* only 0 or all 1s can be written to IA32_MCi_CTL
- * some Linux kernels though clear bit 10 in bank 4 to
- * workaround a BIOS/GART TBL issue on AMD K8s, ignore
- * this to avoid an uncatched #GP in the guest
- */
- if ((offset & 0x3) == 0 &&
- data != 0 && (data | (1 << 10)) != ~(u64)0)
- return -1;
-
- /* MCi_STATUS */
- if (!msr_info->host_initiated &&
- (offset & 0x3) == 1 && data != 0) {
- if (!can_set_mci_status(vcpu))
- return -1;
- }
+ case MSR_IA32_MC0_CTL2 ... MSR_IA32_MCx_CTL2(KVM_MAX_MCE_BANKS) - 1:
+ last_msr = MSR_IA32_MCx_CTL2(bank_num) - 1;
+ if (msr > last_msr)
+ return 1;

- vcpu->arch.mce_banks[offset] = data;
- break;
- }
+ if (!(mcg_cap & MCG_CMCI_P) && (data || !msr_info->host_initiated))
+ return 1;
+ /* An attempt to write a 1 to a reserved bit raises #GP */
+ if (data & ~(MCI_CTL2_CMCI_EN | MCI_CTL2_CMCI_THRESHOLD_MASK))
+ return 1;
+ offset = array_index_nospec(msr - MSR_IA32_MC0_CTL2,
+ last_msr + 1 - MSR_IA32_MC0_CTL2);
+ vcpu->arch.mci_ctl2_banks[offset] = data;
+ break;
+ case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
+ last_msr = MSR_IA32_MCx_CTL(bank_num) - 1;
+ if (msr > last_msr)
+ return 1;
+
+ /*
+ * Only 0 or all 1s can be written to IA32_MCi_CTL, all other
+ * values are architecturally undefined. But, some Linux
+ * kernels clear bit 10 in bank 4 to workaround a BIOS/GART TLB
+ * issue on AMD K8s, allow bit 10 to be clear when setting all
+ * other bits in order to avoid an uncaught #GP in the guest.
+ */
+ if (is_mci_control_msr(msr) &&
+ data != 0 && (data | (1 << 10)) != ~(u64)0)
+ return 1;
+
+ /*
+ * All CPUs allow writing 0 to MCi_STATUS MSRs to clear the MSR.
+ * AMD-based CPUs allow non-zero values, but if and only if
+ * HWCR[McStatusWrEn] is set.
+ */
+ if (!msr_info->host_initiated && is_mci_status_msr(msr) &&
+ data != 0 && !can_set_mci_status(vcpu))
+ return 1;
+
+ offset = array_index_nospec(msr - MSR_IA32_MC0_CTL,
+ last_msr + 1 - MSR_IA32_MC0_CTL);
+ vcpu->arch.mce_banks[offset] = data;
+ break;
+ default:
return 1;
}
return 0;
@@ -3514,7 +3543,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
}
break;
- case 0x200 ... 0x2ff:
+ case 0x200 ... MSR_IA32_MC0_CTL2 - 1:
+ case MSR_IA32_MCx_CTL2(KVM_MAX_MCE_BANKS) ... 0x2ff:
return kvm_mtrr_set_msr(vcpu, msr, data);
case MSR_IA32_APICBASE:
return kvm_set_apic_base(vcpu, msr_info);
@@ -3671,6 +3701,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_IA32_MCG_CTL:
case MSR_IA32_MCG_STATUS:
case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
+ case MSR_IA32_MC0_CTL2 ... MSR_IA32_MCx_CTL2(KVM_MAX_MCE_BANKS) - 1:
return set_msr_mce(vcpu, msr_info);

case MSR_K7_PERFCTR0 ... MSR_K7_PERFCTR3:
@@ -3775,6 +3806,7 @@ static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
u64 data;
u64 mcg_cap = vcpu->arch.mcg_cap;
unsigned bank_num = mcg_cap & 0xff;
+ u32 offset, last_msr;

switch (msr) {
case MSR_IA32_P5_MC_ADDR:
@@ -3792,16 +3824,27 @@ static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
case MSR_IA32_MCG_STATUS:
data = vcpu->arch.mcg_status;
break;
- default:
- if (msr >= MSR_IA32_MC0_CTL &&
- msr < MSR_IA32_MCx_CTL(bank_num)) {
- u32 offset = array_index_nospec(
- msr - MSR_IA32_MC0_CTL,
- MSR_IA32_MCx_CTL(bank_num) - MSR_IA32_MC0_CTL);
+ case MSR_IA32_MC0_CTL2 ... MSR_IA32_MCx_CTL2(KVM_MAX_MCE_BANKS) - 1:
+ last_msr = MSR_IA32_MCx_CTL2(bank_num) - 1;
+ if (msr > last_msr)
+ return 1;

- data = vcpu->arch.mce_banks[offset];
- break;
- }
+ if (!(mcg_cap & MCG_CMCI_P) && !host)
+ return 1;
+ offset = array_index_nospec(msr - MSR_IA32_MC0_CTL2,
+ last_msr + 1 - MSR_IA32_MC0_CTL2);
+ data = vcpu->arch.mci_ctl2_banks[offset];
+ break;
+ case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
+ last_msr = MSR_IA32_MCx_CTL(bank_num) - 1;
+ if (msr > last_msr)
+ return 1;
+
+ offset = array_index_nospec(msr - MSR_IA32_MC0_CTL,
+ last_msr + 1 - MSR_IA32_MC0_CTL);
+ data = vcpu->arch.mce_banks[offset];
+ break;
+ default:
return 1;
}
*pdata = data;
@@ -3898,7 +3941,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
break;
}
case MSR_MTRRcap:
- case 0x200 ... 0x2ff:
+ case 0x200 ... MSR_IA32_MC0_CTL2 - 1:
+ case MSR_IA32_MCx_CTL2(KVM_MAX_MCE_BANKS) ... 0x2ff:
return kvm_mtrr_get_msr(vcpu, msr_info->index, &msr_info->data);
case 0xcd: /* fsb frequency */
msr_info->data = 3;
@@ -4014,6 +4058,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_IA32_MCG_CTL:
case MSR_IA32_MCG_STATUS:
case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
+ case MSR_IA32_MC0_CTL2 ... MSR_IA32_MCx_CTL2(KVM_MAX_MCE_BANKS) - 1:
return get_msr_mce(vcpu, msr_info->index, &msr_info->data,
msr_info->host_initiated);
case MSR_IA32_XSS:
@@ -4769,9 +4814,12 @@ static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
/* Init IA32_MCG_CTL to all 1s */
if (mcg_cap & MCG_CTL_P)
vcpu->arch.mcg_ctl = ~(u64)0;
- /* Init IA32_MCi_CTL to all 1s */
- for (bank = 0; bank < bank_num; bank++)
+ /* Init IA32_MCi_CTL to all 1s, IA32_MCi_CTL2 to all 0s */
+ for (bank = 0; bank < bank_num; bank++) {
vcpu->arch.mce_banks[bank*4] = ~(u64)0;
+ if (mcg_cap & MCG_CMCI_P)
+ vcpu->arch.mci_ctl2_banks[bank] = 0;
+ }
vcpu->arch.apic->nr_lvt_entries =
KVM_APIC_MAX_NR_LVT_ENTRIES - !(mcg_cap & MCG_CMCI_P);

@@ -11228,7 +11276,9 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)

vcpu->arch.mce_banks = kcalloc(KVM_MAX_MCE_BANKS * 4, sizeof(u64),
GFP_KERNEL_ACCOUNT);
- if (!vcpu->arch.mce_banks)
+ vcpu->arch.mci_ctl2_banks = kcalloc(KVM_MAX_MCE_BANKS, sizeof(u64),
+ GFP_KERNEL_ACCOUNT);
+ if (!vcpu->arch.mce_banks || !vcpu->arch.mci_ctl2_banks)
goto fail_free_pio_data;
vcpu->arch.mcg_cap = KVM_MAX_MCE_BANKS;

@@ -11281,6 +11331,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
free_cpumask_var(vcpu->arch.wbinvd_dirty_mask);
fail_free_mce_banks:
kfree(vcpu->arch.mce_banks);
+ kfree(vcpu->arch.mci_ctl2_banks);
fail_free_pio_data:
free_page((unsigned long)vcpu->arch.pio_data);
fail_free_lapic:
@@ -11325,6 +11376,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
kvm_hv_vcpu_uninit(vcpu);
kvm_pmu_destroy(vcpu);
kfree(vcpu->arch.mce_banks);
+ kfree(vcpu->arch.mci_ctl2_banks);
kvm_free_lapic(vcpu);
idx = srcu_read_lock(&vcpu->kvm->srcu);
kvm_mmu_destroy(vcpu);
--
2.36.1.255.ge46751e96f-goog