On Thu, Jun 03, 2021 at 01:48:31PM +0200, Vitaly Kuznetsov wrote:
> To make Hyper-V features appear in e.g. QMP query-cpu-model-expansion we
> need to expand and set the corresponding CPUID leaves early. Modify
> x86_cpu_get_supported_feature_word() to call newly intoduced Hyper-V
> specific kvm_hv_get_supported_cpuid() instead of
> kvm_arch_get_supported_cpuid(). We can't use kvm_arch_get_supported_cpuid()
> as Hyper-V specific CPUID leaves intersect with KVM's.
>
> Note, early expansion will only happen when KVM supports system wide
> KVM_GET_SUPPORTED_HV_CPUID ioctl (KVM_CAP_SYS_HYPERV_CPUID).
>
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
> ---
> target/i386/cpu.c | 4 ++++
> target/i386/kvm/kvm-stub.c | 5 +++++
> target/i386/kvm/kvm.c | 24 ++++++++++++++++++++----
> target/i386/kvm/kvm_i386.h | 1 +
> 4 files changed, 30 insertions(+), 4 deletions(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index b2d8e5713911..159b7aa8f073 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -5990,6 +5990,10 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
> if (env->cpuid_xlevel2 == UINT32_MAX) {
> env->cpuid_xlevel2 = env->cpuid_min_xlevel2;
> }
> +
> + if (kvm_enabled()) {
> + kvm_hyperv_expand_features(cpu, errp);
> + }
> }
>
> /*
> diff --git a/target/i386/kvm/kvm-stub.c b/target/i386/kvm/kvm-stub.c
> index 92f49121b8fa..f6e7e4466e1a 100644
> --- a/target/i386/kvm/kvm-stub.c
> +++ b/target/i386/kvm/kvm-stub.c
> @@ -39,3 +39,8 @@ bool kvm_hv_vpindex_settable(void)
> {
> return false;
> }
> +
> +bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
> +{
> + abort();
> +}
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index a5f8553af921..650fdd970d6e 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -1217,13 +1217,22 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs,
> uint32_t func, int reg)
> * of 'hv_passthrough' mode and fills the environment with all supported
> * Hyper-V features.
> */
> -static bool hyperv_expand_features(CPUState *cs, Error **errp)
> +bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
> {
> - X86CPU *cpu = X86_CPU(cs);
> + CPUState *cs = CPU(cpu);
>
> if (!hyperv_enabled(cpu))
> return true;
>
> + /*
> + * When kvm_hyperv_expand_features is called at CPU feature expansion
> + * time per-CPU kvm_state is not available yet so we can only proceed
> + * when KVM_CAP_SYS_HYPERV_CPUID is supported.
> + */
> + if (!cs->kvm_state &&
> + !kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID))
> + return true;
> +
> if (cpu->hyperv_passthrough) {
> cpu->hyperv_vendor_id[0] =
> hv_cpuid_get_host(cs, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, R_EBX);
> @@ -1565,8 +1574,15 @@ int kvm_arch_init_vcpu(CPUState *cs)
>
> env->apic_bus_freq = KVM_APIC_BUS_FREQUENCY;
>
> - /* Paravirtualization CPUIDs */
> - if (!hyperv_expand_features(cs, &local_err)) {
> + /*
> + * kvm_hyperv_expand_features() is called here for the second time in
> case
> + * KVM_CAP_SYS_HYPERV_CPUID is not supported. While we can't possibly
> handle
> + * 'query-cpu-model-expansion' in this case as we don't have a KVM vCPU
> to
> + * check which Hyper-V enlightenments are supported and which are not, we
> + * can still proceed and check/expand Hyper-V enlightenments here so
> legacy
> + * behavior is preserved.
> + */
Issue we might need to solve later: how can management software
differentiate "Hyper-V enlightenments are not supported at all"
from "we can't tell you which Hyper-V enlightenments are
available because KVM_CAP_SYS_HYPERV_CPUID is unavailable"?
> + if (!kvm_hyperv_expand_features(cpu, &local_err)) {
> error_report_err(local_err);
> return -ENOSYS;
> }
> diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
> index dc725083891c..54667b35f09c 100644
> --- a/target/i386/kvm/kvm_i386.h
> +++ b/target/i386/kvm/kvm_i386.h
> @@ -47,6 +47,7 @@ bool kvm_has_x2apic_api(void);
> bool kvm_has_waitpkg(void);
>
> bool kvm_hv_vpindex_settable(void);
> +bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);
>
> uint64_t kvm_swizzle_msi_ext_dest_id(uint64_t address);
Reviewed-by: Eduardo Habkost <[email protected]>
--
Eduardo
