On Fri, Apr 24, 2020 at 02:37:41PM +0300, Jon Doron wrote:
> Simlify the code to define a new cpuid leaf group by enabled feature.
>
> This also fixes a bug in which the max cpuid leaf was always set to
> HYPERV_CPUID_NESTED_FEATURES regardless if nesting is supported or not.
I'm not sure the bug is there. My understanding is that
HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS is supposed to provide the range
of leaves that return meaningful information.
HYPERV_CPUID_NESTED_FEATURES *can* return meaningful information
regardless of whether nested virt is active.
So I'd rather skip reducing the returned set if !evmcs_ver. The
returned set is sparse in .function anyway; anything that isn't there
will just return zeros to the guest.
Changing the cpuid is also guest-visible so care must be taken with
this.
> Any new CPUID group needs to consider the max leaf and be added in the
> correct order, in this method there are two rules:
> 1. Each cpuid leaf group must be order in an ascending order
> 2. The appending for the cpuid leafs by features also needs to happen by
> ascending order.
It looks like unnecessary complication. I think all you need to do to
simplify adding new leaves is to add a macro to hyperv-tlfs.h, say,
HYPERV_CPUID_MAX_PRESENT_LEAF, define it to
HYPERV_CPUID_NESTED_FEATURES, and redefine once another leaf is added
(compat may need to be taken care of).
Thanks,
Roman.
> Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> Signed-off-by: Jon Doron <arilou@xxxxxxxxx>
> ---
> arch/x86/kvm/hyperv.c | 46 ++++++++++++++++++++++++++++++-------------
> 1 file changed, 32 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index bcefa9d4e57e..ab3e9dbcabbe 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1785,27 +1785,45 @@ int kvm_vm_ioctl_hv_eventfd(struct kvm *kvm, struct kvm_hyperv_eventfd *args)
> return kvm_hv_eventfd_assign(kvm, args->conn_id, args->fd);
> }
>
> +/* Must be sorted in ascending order by function */
> +static struct kvm_cpuid_entry2 core_cpuid_entries[] = {
> + { .function = HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS },
> + { .function = HYPERV_CPUID_INTERFACE },
> + { .function = HYPERV_CPUID_VERSION },
> + { .function = HYPERV_CPUID_FEATURES },
> + { .function = HYPERV_CPUID_ENLIGHTMENT_INFO },
> + { .function = HYPERV_CPUID_IMPLEMENT_LIMITS },
> +};
> +
> +static struct kvm_cpuid_entry2 evmcs_cpuid_entries[] = {
> + { .function = HYPERV_CPUID_NESTED_FEATURES },
> +};
> +
> +#define HV_MAX_CPUID_ENTRIES \
> + (ARRAY_SIZE(core_cpuid_entries) +\
> + ARRAY_SIZE(evmcs_cpuid_entries))
> +
> int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
> struct kvm_cpuid_entry2 __user *entries)
> {
> uint16_t evmcs_ver = 0;
> - struct kvm_cpuid_entry2 cpuid_entries[] = {
> - { .function = HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS },
> - { .function = HYPERV_CPUID_INTERFACE },
> - { .function = HYPERV_CPUID_VERSION },
> - { .function = HYPERV_CPUID_FEATURES },
> - { .function = HYPERV_CPUID_ENLIGHTMENT_INFO },
> - { .function = HYPERV_CPUID_IMPLEMENT_LIMITS },
> - { .function = HYPERV_CPUID_NESTED_FEATURES },
> - };
> - int i, nent = ARRAY_SIZE(cpuid_entries);
> + struct kvm_cpuid_entry2 cpuid_entries[HV_MAX_CPUID_ENTRIES];
> + int i, nent = 0;
> +
> + /* Set the core cpuid entries required for Hyper-V */
> + memcpy(&cpuid_entries[nent], &core_cpuid_entries,
> + sizeof(core_cpuid_entries));
> + nent = ARRAY_SIZE(core_cpuid_entries);
>
> if (kvm_x86_ops.nested_get_evmcs_version)
> evmcs_ver = kvm_x86_ops.nested_get_evmcs_version(vcpu);
>
> - /* Skip NESTED_FEATURES if eVMCS is not supported */
> - if (!evmcs_ver)
> - --nent;
> + if (evmcs_ver) {
> + /* EVMCS is enabled, add the required EVMCS CPUID leafs */
> + memcpy(&cpuid_entries[nent], &evmcs_cpuid_entries,
> + sizeof(evmcs_cpuid_entries));
> + nent += ARRAY_SIZE(evmcs_cpuid_entries);
> + }
>
> if (cpuid->nent < nent)
> return -E2BIG;
> @@ -1821,7 +1839,7 @@ int kvm_vcpu_ioctl_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
> case HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS:
> memcpy(signature, "Linux KVM Hv", 12);
>
> - ent->eax = HYPERV_CPUID_NESTED_FEATURES;
> + ent->eax = cpuid_entries[nent - 1].function;
> ent->ebx = signature[0];
> ent->ecx = signature[1];
> ent->edx = signature[2];
> --
> 2.24.1
>
