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KVM: x86: export paravirtual cpuid flags in KVM_GET_SUPPORTED_CPUID 

Right now, we were using individual KVM_CAP entities to communicate
userspace about which cpuids we support. This is suboptimal, since it
generates a delay between the feature arriving in the host, and
being available at the guest.

A much better mechanism is to list para features in KVM_GET_SUPPORTED_CPUID.
This makes userspace automatically aware of what we provide. And if we
ever add a new cpuid bit in the future, we have to do that again,
which create some complexity and delay in feature adoption.

Signed-off-by: Glauber Costa <glommer@redhat.com>
Acked-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Glauber Costa 2010-05-11 12:17:43 -04:00 committed by Avi Kivity
parent 0e6ac58acb
commit 84478c829d
1 changed files with 34 additions and 0 deletions
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34
arch/x86/kvm/x86.c
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@ -1972,6 +1972,23 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
}
break;
}
case KVM_CPUID_SIGNATURE: {
char signature[12] = "KVMKVMKVM\0\0";
u32 *sigptr = (u32 *)signature;
entry->eax = 0;
entry->ebx = sigptr[0];
entry->ecx = sigptr[1];
entry->edx = sigptr[2];
break;
}
case KVM_CPUID_FEATURES:
entry->eax = (1 << KVM_FEATURE_CLOCKSOURCE) |
(1 << KVM_FEATURE_NOP_IO_DELAY) |
(1 << KVM_FEATURE_CLOCKSOURCE2);
entry->ebx = 0;
entry->ecx = 0;
entry->edx = 0;
break;
case 0x80000000:
entry->eax = min(entry->eax, 0x8000001a);
break;
@ -2018,6 +2035,23 @@ static int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
for (func = 0x80000001; func <= limit && nent < cpuid->nent; ++func)
do_cpuid_ent(&cpuid_entries[nent], func, 0,
&nent, cpuid->nent);
r = -E2BIG;
if (nent >= cpuid->nent)
goto out_free;
do_cpuid_ent(&cpuid_entries[nent], KVM_CPUID_SIGNATURE, 0, &nent,
cpuid->nent);
r = -E2BIG;
if (nent >= cpuid->nent)
goto out_free;
do_cpuid_ent(&cpuid_entries[nent], KVM_CPUID_FEATURES, 0, &nent,
cpuid->nent);
r = -E2BIG;
if (nent >= cpuid->nent)
goto out_free;