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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>
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@ -1972,6 +1972,23 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
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}
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break;
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}
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case KVM_CPUID_SIGNATURE: {
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char signature[12] = "KVMKVMKVM\0\0";
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u32 *sigptr = (u32 *)signature;
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entry->eax = 0;
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entry->ebx = sigptr[0];
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entry->ecx = sigptr[1];
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entry->edx = sigptr[2];
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break;
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}
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case KVM_CPUID_FEATURES:
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entry->eax = (1 << KVM_FEATURE_CLOCKSOURCE) |
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(1 << KVM_FEATURE_NOP_IO_DELAY) |
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(1 << KVM_FEATURE_CLOCKSOURCE2);
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entry->ebx = 0;
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entry->ecx = 0;
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entry->edx = 0;
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break;
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case 0x80000000:
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entry->eax = min(entry->eax, 0x8000001a);
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break;
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@ -2018,6 +2035,23 @@ static int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
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for (func = 0x80000001; func <= limit && nent < cpuid->nent; ++func)
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do_cpuid_ent(&cpuid_entries[nent], func, 0,
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&nent, cpuid->nent);
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r = -E2BIG;
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if (nent >= cpuid->nent)
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goto out_free;
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do_cpuid_ent(&cpuid_entries[nent], KVM_CPUID_SIGNATURE, 0, &nent,
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cpuid->nent);
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r = -E2BIG;
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if (nent >= cpuid->nent)
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goto out_free;
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do_cpuid_ent(&cpuid_entries[nent], KVM_CPUID_FEATURES, 0, &nent,
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cpuid->nent);
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r = -E2BIG;
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if (nent >= cpuid->nent)
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goto out_free;
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