KVM: x86: export paravirtual cpuid flags in KVM_GET_SUPPORTED_CPUID (84478c82) · Commits · 戴 / test

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>

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;

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