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SubjectRe: [PATCH] Add MCE support to KVM
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On Thu, 2009-04-09 at 23:50 +0800, Avi Kivity wrote:
> Huang Ying wrote:
> > +int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> > +{
> > + switch (msr) {
> > + case MSR_EFER:
> > + set_efer(vcpu, data);
> > break;
> > case MSR_IA32_DEBUGCTLMSR:
> > if (!data) {
> > @@ -807,6 +828,8 @@ int kvm_set_msr_common(struct kvm_vcpu *
> > break;
> > }
> > default:
> > + if (!set_msr_mce(vcpu, msr, data))
> > + break;
> > pr_unimpl(vcpu, "unhandled wrmsr: 0x%x data %llx\n", msr, data);
> > return 1;
> > }
> >
>
> Is there any reason you split kvm_set_msr_common() into two functions?

I want to group MCE related MSR together. And most MCE MSR read/write
need to access vcpu->arch.mcg_xxx or vcpu->arch_mce_banks, So I think
use a MCE specific function would be cleaner.

But It seems that something as follow would be better.

kvm_set_msr_comm()
{
switch (msr) {
case MSR_IA32_P5_MC_ADDR:
case MSR_IA32_P5_MC_TYPE:
case MSR_IA32_MCG_CAP:
case MSR_IA32_MCG_CTL:
case MSR_IA32_MCG_STATUS:
case MSR_IA32_MC0_CTL ... MSR_IA32_MC0_MISC + 4 * KVM_MCE_MAX_BANK:
set_msr_mce();
break;
...
}
...
}
> > +
> > +int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> > +{
> > + u64 data;
> > +
> > + switch (msr) {
> > + case 0xc0010010: /* SYSCFG */
> > + case 0xc0010015: /* HWCR */
> >
>
> Please use MSR_ constants (add them if they don't exist yet).

In fact, this is not added by me. But I can change this by the way.

> >
> > +static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
> > + u64 mcg_cap)
> > +{
> > + int r;
> > + unsigned bank_num = mcg_cap & 0xff, bank;
> > + u64 *banks;
> > +
> > + r = -EINVAL;
> > + if (!bank_num)
> > + goto out;
> > + r = -ENOMEM;
> > + banks = kzalloc(bank_num * sizeof(u64) * 4, GFP_KERNEL);
> >
>
> If banks is already allocated, you'll leak it.

Yes. I will fix this.

> Why not always allocate it on vcpu setup?

Because the MCE bank number is not fixed, it is based on mcg_cap from
user space.

> > +static int kvm_vcpu_ioctl_x86_set_mce(struct kvm_vcpu *vcpu,
> > + struct kvm_x86_mce *mce)
> > +{
> > + u64 mcg_cap = vcpu->arch.mcg_cap;
> > + unsigned bank_num = mcg_cap & 0xff;
> > + u64 *banks = vcpu->arch.mce_banks;
> > +
> > + if (mce->bank >= bank_num || !(mce->status & MCI_STATUS_VAL))
> > + return -EINVAL;
> > + /*
> > + * if IA32_MCG_CTL is not all 1s, the uncorrected error
> > + * reporting is disabled
> > + */
> > + if ((mce->status & MCI_STATUS_UC) && (mcg_cap & MCG_CTL_P) &&
> > + vcpu->arch.mcg_ctl != ~(u64)0)
> > + return 0;
> > + banks += 4 * mce->bank;
> > + /*
> > + * if IA32_MCi_CTL is not all 1s, the uncorrected error
> > + * reporting is disabled for the bank
> > + */
> > + if ((mce->status & MCI_STATUS_UC) && banks[0] != ~(u64)0)
> > + return 0;
> > + if (mce->status & MCI_STATUS_UC) {
> > + u64 status = mce->status;
> > + if ((vcpu->arch.mcg_status & MCG_STATUS_MCIP) ||
> > + !(vcpu->arch.cr4 & X86_CR4_MCE)) {
> > + printk(KERN_DEBUG "kvm: set_mce: "
> > + "injects mce exception while "
> > + "previous one is in progress!\n");
> > + set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
> > + return 0;
> > + }
> > + if (banks[1] & MCI_STATUS_VAL)
> > + status |= MCI_STATUS_OVER;
> > + banks[1] = mce->status;
> > + banks[2] = mce->addr;
> > + banks[3] = mce->misc;
> > + vcpu->arch.mcg_status = mce->mcg_status;
> > + kvm_queue_exception(vcpu, MC_VECTOR);
> > + } else if (!(banks[1] & MCI_STATUS_VAL) ||
> > + (!(banks[1] & MCI_STATUS_UC) &&
> > + !((mcg_cap & MCG_TES_P) && ((banks[1]>>53) & 0x3) < 2))) {
> > + u64 status = mce->status;
> > + if (banks[1] & MCI_STATUS_VAL)
> > + status |= MCI_STATUS_OVER;
> > + banks[1] = mce->status;
> > + banks[2] = mce->addr;
> > + banks[3] = mce->misc;
> > + } else
> > + banks[1] |= MCI_STATUS_OVER;
> > + return 0;
> > +}
> >
>
> Can userspace just use KVM_SET_MSR for this?

In addition to assigning MSR, we have some other logic for MCE, such as
BANK reporting disabling, overwriting rules, triple fault for UC MCE
during MCIP. So I think we need some dedicate interface.

> > + case KVM_X86_SETUP_MCE: {
> > + u64 mcg_cap;
> > +
> > + r = -EFAULT;
> > + if (copy_from_user(&mcg_cap, argp, sizeof mcg_cap))
> > + goto out;
> > + /*
> > + * extended machine-check state registers and CMCI are
> > + * not supported.
> > + */
> > + mcg_cap &= ~(MCG_EXT_P|MCG_CMCI_P);
> >
>
> Instead of silently dropping, should return an error.
>
> > + if (copy_to_user(argp, &mcg_cap, sizeof mcg_cap))
> > + goto out;
> >
>
> And not copy.

This is designed as some kind of feature negotiating. Use space request
MCE features via mcg_cap, kernel space remove un-supported features and
return the resulting mcg_cap.

>
> > #define KVM_TRC_SHIFT 16
> > /*
> > * kvm trace categories
> > @@ -528,6 +540,9 @@ struct kvm_irq_routing {
> > #define KVM_NMI _IO(KVMIO, 0x9a)
> > /* Available with KVM_CAP_SET_GUEST_DEBUG */
> > #define KVM_SET_GUEST_DEBUG _IOW(KVMIO, 0x9b, struct kvm_guest_debug)
> > +/* MCE for x86 */
> > +#define KVM_X86_SETUP_MCE _IOWR(KVMIO, 0x9a, __u64)
> > +#define KVM_X86_SET_MCE _IOW(KVMIO, 0x9b, struct kvm_x86_mce)
> >
>
> Please add a KVM_CAP_ to advertise this capability.

Yes. I will do this.

Best Regards,
Huang Ying

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