Eduardo Habkost <ehabk...@redhat.com> writes:
> On Thu, Apr 22, 2021 at 06:11:24PM +0200, Vitaly Kuznetsov wrote:
>> KVM_GET_SUPPORTED_HV_CPUID was made a system wide ioctl which can be called
>> prior to creating vCPUs and we are going to use that to expand Hyper-V cpu
>> features early. Use it when it is supported by KVM.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
>> ---
>> target/i386/kvm/kvm.c | 17 +++++++++++++----
>> 1 file changed, 13 insertions(+), 4 deletions(-)
>>
>> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
>> index feec9f25ba12..5d08f3a39ef7 100644
>> --- a/target/i386/kvm/kvm.c
>> +++ b/target/i386/kvm/kvm.c
>> @@ -928,7 +928,8 @@ static struct {
>> },
>> };
>>
>> -static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max)
>> +static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max,
>> + bool do_sys_ioctl)
>> {
>> struct kvm_cpuid2 *cpuid;
>> int r, size;
>> @@ -937,7 +938,11 @@ static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState
>> *cs, int max)
>> cpuid = g_malloc0(size);
>> cpuid->nent = max;
>>
>> - r = kvm_vcpu_ioctl(cs, KVM_GET_SUPPORTED_HV_CPUID, cpuid);
>> + if (do_sys_ioctl) {
>> + r = kvm_ioctl(kvm_state, KVM_GET_SUPPORTED_HV_CPUID, cpuid);
>> + } else {
>> + r = kvm_vcpu_ioctl(cs, KVM_GET_SUPPORTED_HV_CPUID, cpuid);
>> + }
>> if (r == 0 && cpuid->nent >= max) {
>> r = -E2BIG;
>> }
>> @@ -964,13 +969,17 @@ static struct kvm_cpuid2
>> *get_supported_hv_cpuid(CPUState *cs)
>> /* 0x40000000..0x40000005, 0x4000000A, 0x40000080..0x40000080 leaves */
>> int max = 10;
>> int i;
>> + bool do_sys_ioctl;
>> +
>> + do_sys_ioctl =
>> + kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID) > 0;
>>
>> /*
>> * When the buffer is too small, KVM_GET_SUPPORTED_HV_CPUID fails with
>> * -E2BIG, however, it doesn't report back the right size. Keep
>> increasing
>> * it and re-trying until we succeed.
>> */
>> - while ((cpuid = try_get_hv_cpuid(cs, max)) == NULL) {
>> + while ((cpuid = try_get_hv_cpuid(cs, max, do_sys_ioctl)) == NULL) {
>> max++;
>> }
>>
>> @@ -980,7 +989,7 @@ static struct kvm_cpuid2
>> *get_supported_hv_cpuid(CPUState *cs)
>> * information early, just check for the capability and set the bit
>> * manually.
>> */
>> - if (kvm_check_extension(cs->kvm_state,
>> + if (!do_sys_ioctl && kvm_check_extension(cs->kvm_state,
>> KVM_CAP_HYPERV_ENLIGHTENED_VMCS) > 0) {
>
> Oh, this conditional replaces the comment I suggested in patch
> 10/19. It makes it obvious that the hack can be deleted if we
> remove support for the VCPU ioctl.
>
> So, when exactly will we be able to delete the VCPU ioctl code
> and support only the system ioctl?
When QEMU drops support for kernels < 5.11? Note, current RHEL8 already
supports system version so we're talking about upstream kernels/Ubuntu
LTS/...
I remember there was a list of supported kernels for QEMU somewhere but
don't seem to be able to find it quickly, could you maybe point me in
the right direction?
>
> Reviewed-by: Eduardo Habkost <ehabk...@redhat.com>
>
Thanks!
>> for (i = 0; i < cpuid->nent; i++) {
>> if (cpuid->entries[i].function == HV_CPUID_ENLIGHTMENT_INFO) {
>> --
>> 2.30.2
>>
--
Vitaly
