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Commit 84478c82 authored by Glauber Costa's avatar Glauber Costa Committed by Avi Kivity
Browse files

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: default avatarGlauber Costa <glommer@redhat.com>
Acked-by: default avatarZachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 0e6ac58a

arch/x86/kvm/x86.c

+34 −0
Original line number Diff line number Diff line
@@ -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;