Is this interface supposed to support changing MSR handing at runtime
or is the ioctl only meant to be called prior to KVM_RUN?
Thanks,
Richard
On Wed, Oct 28, 2009 at 1:23 PM, David Windsor <dwindsor@xxxxxxxxx> wrote:
>
> Hi,
>
> I've encountered a situation in which I would like to allow userspace
> to set the MSRs which KVM should not emulate and instead implement
> these as no-ops.
>
> I have not seen any work in this space, furthermore there is an item
> on the KVM TODO that is very similar to what I'm trying to do.
>
> The userspace interface is an extension of kvm_vcpu_ioctl, adding the
> KVM_SET_MSRS_NOOP flag. It takes a struct kvm_msrs as a list of which
> MSRs should be no-ops and adds the field noop to struct kvm_msr_entry.
> This patch only affects vmx, but if the approach is sane, I can
> extend it to support svm as well.
>
>
>
> diff -purN linux-2.6.32-rc5/arch/x86/include/asm/kvm.h
> linux-2.6.32-rc5-kvm-msrs-noop/arch/x86/include/asm/kvm.h
> --- linux-2.6.32-rc5/arch/x86/include/asm/kvm.h 2009-10-15
> 20:41:50.000000000 -0400
> +++ linux-2.6.32-rc5-kvm-msrs-noop/arch/x86/include/asm/kvm.h 2009-10-27
> 22:44:58.000000000 -0400
> @@ -144,6 +144,7 @@ struct kvm_msr_entry {
> __u32 index;
> __u32 reserved;
> __u64 data;
> + __u8 noop;
> };
>
> /* for KVM_GET_MSRS and KVM_SET_MSRS */
> diff -purN linux-2.6.32-rc5/arch/x86/include/asm/kvm_host.h
> linux-2.6.32-rc5-kvm-msrs-noop/arch/x86/include/asm/kvm_host.h
> --- linux-2.6.32-rc5/arch/x86/include/asm/kvm_host.h 2009-10-15
> 20:41:50.000000000 -0400
> +++ linux-2.6.32-rc5-kvm-msrs-noop/arch/x86/include/asm/kvm_host.h
> 2009-10-27
> 22:44:58.000000000 -0400
> @@ -481,6 +481,7 @@ struct kvm_x86_ops {
> struct kvm_guest_debug *dbg);
> int (*get_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata);
> int (*set_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
> + int (*set_msr_noop)(struct kvm_vcpu *vcpu, u32 msr_index);
> u64 (*get_segment_base)(struct kvm_vcpu *vcpu, int seg);
> void (*get_segment)(struct kvm_vcpu *vcpu,
> struct kvm_segment *var, int seg);
> diff -purN linux-2.6.32-rc5/arch/x86/kvm/vmx.c
> linux-2.6.32-rc5-kvm-msrs-noop/arch/x86/kvm/vmx.c
> --- linux-2.6.32-rc5/arch/x86/kvm/vmx.c 2009-10-15 20:41:50.000000000 -0400
> +++ linux-2.6.32-rc5-kvm-msrs-noop/arch/x86/kvm/vmx.c 2009-10-27
> 22:44:58.000000000 -0400
> @@ -983,6 +983,13 @@ static int vmx_get_msr(struct kvm_vcpu *
> return -EINVAL;
> }
>
> + msr = find_msr_entry(to_vmx(vcpu), msr_index);
> + if (msr) {
> + if (msr->noop) {
> + return 0;
> + }
> + }
> +
> switch (msr_index) {
> #ifdef CONFIG_X86_64
> case MSR_FS_BASE:
> @@ -1032,6 +1039,13 @@ static int vmx_set_msr(struct kvm_vcpu *
> u64 host_tsc;
> int ret = 0;
>
> + msr = find_msr_entry(to_vmx(vcpu), msr_index);
> + if (msr) {
> + if (msr->noop) {
> + return ret;
> + }
> + }
> +
> switch (msr_index) {
> case MSR_EFER:
> vmx_load_host_state(vmx);
> @@ -1078,6 +1092,21 @@ static int vmx_set_msr(struct kvm_vcpu *
> return ret;
> }
>
> +static int vmx_set_msr_noop(struct kvm_vcpu *vcpu, u32 msr)
> +{
> + struct kvm_msr_entry *m;
> +
> + if (!vcpu)
> + return -1;
> +
> + m = find_msr_entry(to_vmx(vcpu), msr);
> + if (!m)
> + return -1;
> +
> + m->noop = 1;
> + return 0;
> +}
> +
> static void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
> {
> __set_bit(reg, (unsigned long *)&vcpu->arch.regs_avail);
> @@ -3942,6 +3971,7 @@ static struct kvm_x86_ops vmx_x86_ops =
> .set_guest_debug = set_guest_debug,
> .get_msr = vmx_get_msr,
> .set_msr = vmx_set_msr,
> + .set_msr_noop = vmx_set_msr_noop,
> .get_segment_base = vmx_get_segment_base,
> .get_segment = vmx_get_segment,
> .set_segment = vmx_set_segment,
> diff -purN linux-2.6.32-rc5/arch/x86/kvm/x86.c
> linux-2.6.32-rc5-kvm-msrs-noop/arch/x86/kvm/x86.c
> --- linux-2.6.32-rc5/arch/x86/kvm/x86.c 2009-10-15 20:41:50.000000000 -0400
> +++ linux-2.6.32-rc5-kvm-msrs-noop/arch/x86/kvm/x86.c 2009-10-27
> 22:44:58.000000000 -0400
> @@ -975,6 +975,31 @@ int kvm_get_msr(struct kvm_vcpu *vcpu, u
> return kvm_x86_ops->get_msr(vcpu, msr_index, pdata);
> }
>
> +static int kvm_set_msrs_noop(struct kvm_vcpu *vcpu, struct kvm_msrs
> __user *user_msrs)
> +{
> + int i, r;
> + int size;
> + struct kvm_msrs msrs;
> + struct kvm_msr_entry *entries;
> +
> + if (copy_from_user(&msrs, user_msrs, sizeof msrs))
> + goto out;
> +
> + size = sizeof(struct kvm_msr_entry) * msrs.nmsrs;
> + if (copy_from_user(entries, user_msrs->entries, size))
> + goto out;
> +
> + for (i = 0; i < msrs.nmsrs; i++) {
> + r = kvm_x86_ops->set_msr_noop(vcpu, entries[i].index);
> + if (r)
> + goto out;
> + }
> +
> + return 0;
> +out:
> + return -1;
> +}
> +
> static int get_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> {
> u64 *p = (u64 *)&vcpu->arch.mtrr_state.fixed_ranges;
> @@ -1864,6 +1889,9 @@ long kvm_arch_vcpu_ioctl(struct file *fi
> case KVM_SET_MSRS:
> r = msr_io(vcpu, argp, do_set_msr, 0);
> break;
> + case KVM_SET_MSRS_NOOP:
> + r = kvm_set_msrs_noop(vcpu, argp);
> + break;
> case KVM_TPR_ACCESS_REPORTING: {
> struct kvm_tpr_access_ctl tac;
>
> diff -purN linux-2.6.32-rc5/include/linux/kvm.h
> linux-2.6.32-rc5-kvm-msrs-noop/include/linux/kvm.h
> --- linux-2.6.32-rc5/include/linux/kvm.h 2009-10-15
> 20:41:50.000000000 -0400
> +++ linux-2.6.32-rc5-kvm-msrs-noop/include/linux/kvm.h 2009-10-27
> 22:46:36.000000000 -0400
> @@ -593,6 +593,7 @@ struct kvm_irqfd {
> #define KVM_X86_SETUP_MCE _IOW(KVMIO, 0x9c, __u64)
> #define KVM_X86_GET_MCE_CAP_SUPPORTED _IOR(KVMIO, 0x9d, __u64)
> #define KVM_X86_SET_MCE _IOW(KVMIO, 0x9e, struct kvm_x86_mce)
> +#define KVM_SET_MSRS_NOOP _IOW(KVMIO, 0x9f, struct kvm_msrs)
>
> /*
> * Deprecated interfaces
> --
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