On Thu, 2020-10-01 at 15:05 +0200, Vitaly Kuznetsov wrote:
> As a preparatory step to allocating vcpu->arch.cpuid_entries dynamically
> make kvm_check_cpuid() check work with an arbitrary 'struct kvm_cpuid_entry2'
> array.
>
> Currently, when kvm_check_cpuid() fails we reset vcpu->arch.cpuid_nent to
> 0 and this is kind of weird, i.e. one would expect CPUIDs to remain
> unchanged when KVM_SET_CPUID[2] call fails.
Since this specific patch doesn't fix this, maybe move this chunk to following patches,
or to the cover letter?
>
> No functional change intended. It would've been possible to move the updated
> kvm_check_cpuid() in kvm_vcpu_ioctl_set_cpuid2() and check the supplied
> input before we start updating vcpu->arch.cpuid_entries/nent but we
> can't do the same in kvm_vcpu_ioctl_set_cpuid() as we'll have to copy
> 'struct kvm_cpuid_entry' entries first. The change will be made when
> vcpu->arch.cpuid_entries[] array becomes allocated dynamically.
>
> Suggested-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> arch/x86/kvm/cpuid.c | 38 +++++++++++++++++++++++---------------
> 1 file changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 37c3668a774f..529348ddedc1 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -54,7 +54,24 @@ static u32 xstate_required_size(u64 xstate_bv, bool compacted)
>
> #define F feature_bit
>
> -static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
> +static inline struct kvm_cpuid_entry2 *cpuid_entry2_find(
> + struct kvm_cpuid_entry2 *entries, int nent, u32 function, u32 index)
> +{
> + struct kvm_cpuid_entry2 *e;
> + int i;
> +
> + for (i = 0; i < nent; i++) {
> + e = &entries[i];
> +
> + if (e->function == function && (e->index == index ||
> + !(e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX)))
> + return e;
> + }
> +
> + return NULL;
> +}
> +
> +static int kvm_check_cpuid(struct kvm_cpuid_entry2 *entries, int nent)
> {
> struct kvm_cpuid_entry2 *best;
>
> @@ -62,7 +79,7 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
> * The existing code assumes virtual address is 48-bit or 57-bit in the
> * canonical address checks; exit if it is ever changed.
> */
> - best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
> + best = cpuid_entry2_find(entries, nent, 0x80000008, 0);
> if (best) {
> int vaddr_bits = (best->eax & 0xff00) >> 8;
>
> @@ -220,7 +237,7 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
> vcpu->arch.cpuid_entries[i].padding[2] = 0;
> }
> vcpu->arch.cpuid_nent = cpuid->nent;
> - r = kvm_check_cpuid(vcpu);
> + r = kvm_check_cpuid(vcpu->arch.cpuid_entries, cpuid->nent);
> if (r) {
> vcpu->arch.cpuid_nent = 0;
> kvfree(cpuid_entries);
> @@ -250,7 +267,7 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
> cpuid->nent * sizeof(struct kvm_cpuid_entry2)))
> goto out;
> vcpu->arch.cpuid_nent = cpuid->nent;
> - r = kvm_check_cpuid(vcpu);
> + r = kvm_check_cpuid(vcpu->arch.cpuid_entries, cpuid->nent);
> if (r) {
> vcpu->arch.cpuid_nent = 0;
> goto out;
> @@ -940,17 +957,8 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
> struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
> u32 function, u32 index)
> {
> - struct kvm_cpuid_entry2 *e;
> - int i;
> -
> - for (i = 0; i < vcpu->arch.cpuid_nent; ++i) {
> - e = &vcpu->arch.cpuid_entries[i];
> -
> - if (e->function == function && (e->index == index ||
> - !(e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX)))
> - return e;
> - }
> - return NULL;
> + return cpuid_entry2_find(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent,
> + function, index);
> }
> EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);
>
Other than minor note to the commit message, this looks fine, so
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
