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[2/3] x86/kvm: Implement MSR_HWCR support

Message ID 20180622095101.32587-3-bp@alien8.de (mailing list archive)
State New, archived
Headers show

Commit Message

Borislav Petkov June 22, 2018, 9:51 a.m. UTC 
From: Borislav Petkov <bp@suse.de>

The hardware configuration register has some useful bits which can be
used by guests. Implement McStatusWrEn which can be used by guests when
injecting MCEs with the in-kernel mce-inject module.

For that, we need to set bit 18 - McStatusWrEn - first, before writing
the MCi_STATUS registers (otherwise we #GP).

Add the required machinery to do so.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/kvm/svm.c | 12 +++++++++---
 arch/x86/kvm/x86.c | 34 +++++++++++++++++++++++++++++++---
 2 files changed, 40 insertions(+), 6 deletions(-)

Comments

Radim Krčmář June 22, 2018, 6:52 p.m. UTC | #1 
2018-06-22 11:51+0200, Borislav Petkov:
> From: Borislav Petkov <bp@suse.de>
> 
> The hardware configuration register has some useful bits which can be
> used by guests. Implement McStatusWrEn which can be used by guests when
> injecting MCEs with the in-kernel mce-inject module.
> 
> For that, we need to set bit 18 - McStatusWrEn - first, before writing
> the MCi_STATUS registers (otherwise we #GP).
> 
> Add the required machinery to do so.
> 
> Signed-off-by: Borislav Petkov <bp@suse.de>
> ---
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> @@ -2146,6 +2146,30 @@ static void kvmclock_sync_fn(struct work_struct *work)
>  					KVMCLOCK_SYNC_PERIOD);
>  }
>  
> +/*
> + * On AMD, HWCR[McStatusWrEn] controls whether setting MCi_STATUS results in #GP.
> + */
> +static bool __set_mci_status(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> +{
> +	if (guest_cpuid_is_amd(vcpu)) {
> +		struct msr_data tmp;
> +
> +		tmp.index = MSR_K7_HWCR;
> +
> +		if (kvm_x86_ops->get_msr(vcpu, &tmp))
> +			return false;
> +
> +		/* McStatusWrEn enabled? */
> +		if (tmp.data & BIT_ULL(18))
> +			return true;
> +	}
> +
> +	if (!msr_info->host_initiated && msr_info->data != 0)
> +		return false;

msr_info->host_initiated is always going to return true, so it would be
better to put it outside of __set_mci_status.

Maybe we could just write the whole logic inline, otherwise I'd call it
something like mci_status_is_writeable.

>  static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  {
>  	u64 mcg_cap = vcpu->arch.mcg_cap;
> @@ -2176,9 +2200,13 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  			if ((offset & 0x3) == 0 &&
>  			    data != 0 && (data | (1 << 10)) != ~(u64)0)
>  				return -1;
> -			if (!msr_info->host_initiated &&
> -				(offset & 0x3) == 1 && data != 0)
> -				return -1;
> +
> +			/* MCi_STATUS */
> +			if ((offset & 0x3) == 1) {
> +				if (!__set_mci_status(vcpu, msr_info))
> +					return -1;
> +			}

			if (!msr_info->host_initiated &&
			    (offset & 0x3) == 1 && data != 0) {
				struct msr_data tmp = {.index = MSR_K7_HWCR};

				if (!guest_cpuid_is_amd(vcpu) ||
				    !kvm_x86_ops->get_msr(vcpu, &tmp) ||
				    !(tmp.data & BIT_ULL(18)))
					return -1;
			}

> +
>  			vcpu->arch.mce_banks[offset] = data;
>  			break;
>  		}
> -- 
> 2.17.0.582.gccdcbd54c
>
Borislav Petkov June 22, 2018, 7:09 p.m. UTC | #2 
On Fri, Jun 22, 2018 at 08:52:38PM +0200, Radim Krčmář wrote:
> msr_info->host_initiated is always going to return true, so it would be
> better to put it outside of __set_mci_status.
> 
> Maybe we could just write the whole logic inline, otherwise I'd call it
> something like mci_status_is_writeable.
> 
> >  static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >  {
> >  	u64 mcg_cap = vcpu->arch.mcg_cap;
> > @@ -2176,9 +2200,13 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >  			if ((offset & 0x3) == 0 &&
> >  			    data != 0 && (data | (1 << 10)) != ~(u64)0)
> >  				return -1;
> > -			if (!msr_info->host_initiated &&
> > -				(offset & 0x3) == 1 && data != 0)
> > -				return -1;
> > +
> > +			/* MCi_STATUS */
> > +			if ((offset & 0x3) == 1) {
> > +				if (!__set_mci_status(vcpu, msr_info))
> > +					return -1;
> > +			}
> 
> 			if (!msr_info->host_initiated &&
> 			    (offset & 0x3) == 1 && data != 0) {
> 				struct msr_data tmp = {.index = MSR_K7_HWCR};
> 
> 				if (!guest_cpuid_is_amd(vcpu) ||
> 				    !kvm_x86_ops->get_msr(vcpu, &tmp) ||
> 				    !(tmp.data & BIT_ULL(18)))
> 					return -1;

Don't you feel it is cleaner if all the MCi_STATUS checking is done in
a separate function? The indentation level and the bunch of checks in
set_msr_mce() make it hard to read while having a separate function
separates it and makes it easier to follow.

I mean, you're the maintainer but if I may give a suggestion, moving the
whole logic into a separate function would be more readable.

And then do:

	if (!msr_info->host_initiated) {
		if (check_mci_status(...))
			return -1;
	}

Something like that...
Radim Krčmář June 22, 2018, 7:22 p.m. UTC | #3 
2018-06-22 21:09+0200, Borislav Petkov:
> On Fri, Jun 22, 2018 at 08:52:38PM +0200, Radim Krčmář wrote:
> > msr_info->host_initiated is always going to return true, so it would be
> > better to put it outside of __set_mci_status.
> > 
> > Maybe we could just write the whole logic inline, otherwise I'd call it
> > something like mci_status_is_writeable.
> > 
> > >  static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > >  {
> > >  	u64 mcg_cap = vcpu->arch.mcg_cap;
> > > @@ -2176,9 +2200,13 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > >  			if ((offset & 0x3) == 0 &&
> > >  			    data != 0 && (data | (1 << 10)) != ~(u64)0)
> > >  				return -1;
> > > -			if (!msr_info->host_initiated &&
> > > -				(offset & 0x3) == 1 && data != 0)
> > > -				return -1;
> > > +
> > > +			/* MCi_STATUS */
> > > +			if ((offset & 0x3) == 1) {
> > > +				if (!__set_mci_status(vcpu, msr_info))
> > > +					return -1;
> > > +			}
> > 
> > 			if (!msr_info->host_initiated &&
> > 			    (offset & 0x3) == 1 && data != 0) {
> > 				struct msr_data tmp = {.index = MSR_K7_HWCR};
> > 
> > 				if (!guest_cpuid_is_amd(vcpu) ||
> > 				    !kvm_x86_ops->get_msr(vcpu, &tmp) ||
> > 				    !(tmp.data & BIT_ULL(18)))
> > 					return -1;
> 
> Don't you feel it is cleaner if all the MCi_STATUS checking is done in
> a separate function? The indentation level and the bunch of checks in
> set_msr_mce() make it hard to read while having a separate function
> separates it and makes it easier to follow.

Yes, I feel the same.

> I mean, you're the maintainer but if I may give a suggestion, moving the
> whole logic into a separate function would be more readable.
> 
> And then do:
> 
> 	if (!msr_info->host_initiated) {
> 		if (check_mci_status(...))
> 			return -1;
> 	}
> 
> Something like that...

Much better, thanks.
diff mbox

Patch

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 72e60daf3ab8..623be0034f7d 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -251,6 +251,9 @@  struct vcpu_svm {
 
 	/* which host CPU was used for running this vcpu */
 	unsigned int last_cpu;
+
+	/* MSRC001_0015 Hardware Configuration */
+	u64 msr_hwcr;
 };
 
 /*
@@ -4154,7 +4157,7 @@  static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		msr_info->data = svm->msr_decfg;
 		break;
 	case MSR_K7_HWCR:
-		msr_info->data = 0;
+		msr_info->data = svm->msr_hwcr;
 		break;
 	default:
 		return kvm_get_msr_common(vcpu, msr_info);
@@ -4364,8 +4367,11 @@  static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		data &= ~(u64)0x40;	/* ignore flush filter disable */
 		data &= ~(u64)0x100;	/* ignore ignne emulation enable */
 		data &= ~(u64)0x8;	/* ignore TLB cache disable */
-		data &= ~(u64)0x40000;  /* ignore Mc status write enable */
-		if (data != 0) {
+
+		/* Handle McStatusWrEn */
+		if (data == BIT_ULL(18)) {
+			svm->msr_hwcr = data;
+		} else if (data != 0) {
 			vcpu_unimpl(vcpu, "unimplemented HWCR wrmsr: 0x%llx\n",
 				    data);
 			return 1;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3bf721c22124..80452b0f0e8c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2146,6 +2146,30 @@  static void kvmclock_sync_fn(struct work_struct *work)
 					KVMCLOCK_SYNC_PERIOD);
 }
 
+/*
+ * On AMD, HWCR[McStatusWrEn] controls whether setting MCi_STATUS results in #GP.
+ */
+static bool __set_mci_status(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
+{
+	if (guest_cpuid_is_amd(vcpu)) {
+		struct msr_data tmp;
+
+		tmp.index = MSR_K7_HWCR;
+
+		if (kvm_x86_ops->get_msr(vcpu, &tmp))
+			return false;
+
+		/* McStatusWrEn enabled? */
+		if (tmp.data & BIT_ULL(18))
+			return true;
+	}
+
+	if (!msr_info->host_initiated && msr_info->data != 0)
+		return false;
+
+	return true;
+}
+
 static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
 	u64 mcg_cap = vcpu->arch.mcg_cap;
@@ -2176,9 +2200,13 @@  static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			if ((offset & 0x3) == 0 &&
 			    data != 0 && (data | (1 << 10)) != ~(u64)0)
 				return -1;
-			if (!msr_info->host_initiated &&
-				(offset & 0x3) == 1 && data != 0)
-				return -1;
+
+			/* MCi_STATUS */
+			if ((offset & 0x3) == 1) {
+				if (!__set_mci_status(vcpu, msr_info))
+					return -1;
+			}
+
 			vcpu->arch.mce_banks[offset] = data;
 			break;
 		}