diff options
| author | Roman Kagan <rkagan@virtuozzo.com> | 2017-06-22 16:51:01 +0300 |
|---|---|---|
| committer | Radim Krčmář <rkrcmar@redhat.com> | 2017-07-13 17:41:04 +0200 |
| commit | efc479e6900c22bad9a2b649d13405ed9cde2d53 (patch) | |
| tree | 517b287129af96017f2aad22e7dd352ce725cbe6 /arch/x86/kvm/hyperv.c | |
| parent | a826faf108e2d855929342268e68c43ba667379a (diff) | |
kvm: x86: hyperv: add KVM_CAP_HYPERV_SYNIC2
There is a flaw in the Hyper-V SynIC implementation in KVM: when message
page or event flags page is enabled by setting the corresponding msr,
KVM zeroes it out. This is problematic because on migration the
corresponding MSRs are loaded on the destination, so the content of
those pages is lost.
This went unnoticed so far because the only user of those pages was
in-KVM hyperv synic timers, which could continue working despite that
zeroing.
Newer QEMU uses those pages for Hyper-V VMBus implementation, and
zeroing them breaks the migration.
Besides, in newer QEMU the content of those pages is fully managed by
QEMU, so zeroing them is undesirable even when writing the MSRs from the
guest side.
To support this new scheme, introduce a new capability,
KVM_CAP_HYPERV_SYNIC2, which, when enabled, makes sure that the synic
pages aren't zeroed out in KVM.
Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Diffstat (limited to 'arch/x86/kvm/hyperv.c')
| -rw-r--r-- | arch/x86/kvm/hyperv.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index ebae57ac5902..a8084406707e 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -221,7 +221,8 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic, synic->version = data; break; case HV_X64_MSR_SIEFP: - if (data & HV_SYNIC_SIEFP_ENABLE) + if ((data & HV_SYNIC_SIEFP_ENABLE) && !host && + !synic->dont_zero_synic_pages) if (kvm_clear_guest(vcpu->kvm, data & PAGE_MASK, PAGE_SIZE)) { ret = 1; @@ -232,7 +233,8 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic, synic_exit(synic, msr); break; case HV_X64_MSR_SIMP: - if (data & HV_SYNIC_SIMP_ENABLE) + if ((data & HV_SYNIC_SIMP_ENABLE) && !host && + !synic->dont_zero_synic_pages) if (kvm_clear_guest(vcpu->kvm, data & PAGE_MASK, PAGE_SIZE)) { ret = 1; @@ -687,14 +689,17 @@ void kvm_hv_vcpu_init(struct kvm_vcpu *vcpu) stimer_init(&hv_vcpu->stimer[i], i); } -int kvm_hv_activate_synic(struct kvm_vcpu *vcpu) +int kvm_hv_activate_synic(struct kvm_vcpu *vcpu, bool dont_zero_synic_pages) { + struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu); + /* * Hyper-V SynIC auto EOI SINT's are * not compatible with APICV, so deactivate APICV */ kvm_vcpu_deactivate_apicv(vcpu); - vcpu_to_synic(vcpu)->active = true; + synic->active = true; + synic->dont_zero_synic_pages = dont_zero_synic_pages; return 0; } |