From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: [PATCH 5/9] export paravirtual cpuid flags in KVM_GET_SUPPORTED_CPUID Date: Tue, 11 May 2010 12:17:43 -0400 Message-ID: <1273594667-17175-6-git-send-email-glommer@redhat.com> References: <1273594667-17175-1-git-send-email-glommer@redhat.com> <1273594667-17175-2-git-send-email-glommer@redhat.com> <1273594667-17175-3-git-send-email-glommer@redhat.com> <1273594667-17175-4-git-send-email-glommer@redhat.com> <1273594667-17175-5-git-send-email-glommer@redhat.com> Cc: linux-kernel@vger.kernel.org, avi@redhat.com, zamsden@redhat.com To: kvm@vger.kernel.org Return-path: In-Reply-To: <1273594667-17175-5-git-send-email-glommer@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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 --- arch/x86/kvm/x86.c | 34 ++++++++++++++++++++++++++++++++++ 1 files changed, 34 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index eb84947..a51b560 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1971,6 +1971,23 @@ 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; @@ -2017,6 +2034,23 @@ 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; -- 1.6.2.2