Hyper-V TLFS specifies this enlightenment as:
"NoNonArchitecturalCoreSharing - Indicates that a virtual processor will never
share a physical core with another virtual processor, except for virtual
processors that are reported as sibling SMT threads. This can be used as an
optimization to avoid the performance overhead of STIBP".
However, STIBP is not the only implication. It was found that Hyper-V on
KVM doesn't pass MD_CLEAR bit to its guests if it doesn't see
NoNonArchitecturalCoreSharing bit.
KVM reports NoNonArchitecturalCoreSharing in KVM_GET_SUPPORTED_HV_CPUID to
indicate that SMT on the host is impossible (not supported of forcefully
disabled).
Implement NoNonArchitecturalCoreSharing support in QEMU as tristate:
'off' - the feature is disabled (default)
'on' - the feature is enabled. This is only safe if vCPUS are properly
pinned and correct topology is exposed. As CPU pinning is done outside
of QEMU the enablement decision will be made on a higher level.
'auto' - copy KVM setting. As during live migration SMT settings on the
source and destination host may differ this requires us to add a migration
blocker.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20191018163908.10246-1-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Hyper-V on KVM can only use Synthetic timers with Direct Mode (opting for
an interrupt instead of VMBus message). This new capability is only
announced in KVM_GET_SUPPORTED_HV_CPUID.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20190517141924.19024-10-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Adds a new CPU flag to enable the Enlightened VMCS KVM feature.
QEMU enables KVM_CAP_HYPERV_ENLIGHTENED_VMCS and gets back the
version to be advertised in lower 16 bits of CPUID.0x4000000A:EAX.
Suggested-by: Ladi Prosek <lprosek@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20181022165506.30332-3-vkuznets@redhat.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Some parts of the Hyper-V hypervisor-guest interface appear to be
target-independent, so move them into a proper header.
Not that Hyper-V ARM64 emulation is around the corner but it seems more
conveninent to have most of Hyper-V and VMBus target-independent, and
allows to avoid conflicts with inclusion of arch-specific headers down
the road in VMBus implementation.
Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
Message-Id: <20180921082041.29380-2-rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Hyper-V PV IPI support is merged to KVM, enable the feature in Qemu. When
enabled, this allows Windows guests to send IPIs to other vCPUs with a
single hypercall even when there are >64 vCPUs in the request.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Message-Id: <20181009130853.6412-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add support for Hyper-V TLB flush which recently got added to KVM.
Just like regular Hyper-V we announce HV_EX_PROCESSOR_MASKS_RECOMMENDED
regardless of how many vCPUs we have. Windows is 'smart' and uses less
expensive non-EX Hypercall whenever possible (when it wants to flush TLB
for all vCPUs or the maximum vCPU index in the vCPU set requires flushing
is less than 64).
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20180610184927.19309-1-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
KVM recently gained support for Hyper-V Reenlightenment MSRs which are
required to make KVM-on-Hyper-V enable TSC page clocksource to its guests
when INVTSC is not passed to it (and it is not passed by default in Qemu
as it effectively blocks migration).
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20180411115036.31832-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The definitions for Hyper-V emulation are currently taken from a header
imported from the Linux kernel.
However, as these describe a third-party protocol rather than a kernel
API, it probably wasn't a good idea to publish it in the kernel uapi.
This patch introduces a header that provides all the necessary
definitions, superseding the one coming from the kernel.
The new header supports (temporary) coexistence with the kernel one.
The constants explicitly named in the Hyper-V specification (e.g. msr
numbers) are defined in a non-conflicting way. Other constants and
types have got new names.
While at this, the protocol data structures are defined in a more
conventional way, without bitfields, enums, and excessive unions.
The code using this stuff is adjusted, too; it can now be built both
with and without the kernel header in the tree.
Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
Message-Id: <20170713201522.13765-2-rkagan@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Vitaly Kuznetsov
Roman Kagan