To date, VMM-directed TSC synchronization and migration has been a bit
messy. KVM has some baked-in heuristics around TSC writes to infer if
the VMM is attempting to synchronize. This is problematic, as it depends
on host userspace writing to the guest's TSC within 1 second of the last
write.
A much cleaner approach to configuring the guest's views of the TSC is to
simply migrate the TSC offset for every vCPU. Offsets are idempotent,
and thus not subject to change depending on when the VMM actually
reads/writes values from/to KVM. The VMM can then read the TSC once with
KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when
the guest is paused.
Cc: David Matlack <dmatlack@google.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210916181538.968978-8-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
As warned with make htmldocs:
.../Documentation/virt/kvm/devices/vcpu.rst:70: WARNING: Malformed table.
Text in column margin in table line 2.
======= ======================================================
-ENODEV: PMUv3 not supported or GIC not initialized
-ENXIO: PMUv3 not properly configured or in-kernel irqchip not
configured as required prior to calling this attribute
-EBUSY: PMUv3 already initialized
-EINVAL: Invalid filter range
======= ======================================================
The ':' character for two lines are above the size of the column.
Besides that, other tables at the file doesn't use ':', so
just drop them.
While here, also fix this warning also introduced at the same patch:
.../Documentation/virt/kvm/devices/vcpu.rst:88: WARNING: Block quote ends without a blank line; unexpected unindent.
By marking the C code as a literal block.
Fixes: 8be86a5eec ("KVM: arm64: Document PMU filtering API")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/b5385dd0213f1f070667925bf7a807bf5270ba78.1601616399.git.mchehab+huawei@kernel.org
KVM_ARM_VCPU_PMU_V3_IRQ returns -EFAULT if get_user() fails when reading
the interrupt number from kvm_device_attr.addr.
KVM_ARM_VCPU_PMU_V3_INIT returns the error value from kvm_vgic_set_owner().
kvm_arm_pmu_v3_init() checks that the vgic has been initialized and the
interrupt number is valid, but kvm_vgic_set_owner() can still return the
error code -EEXIST if another device has already claimed the interrupt.
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Link: https://lore.kernel.org/r/20200924123731.268177-2-alexandru.elisei@arm.com
Add a small blurb describing how the event filtering API gets used.
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
- Use title markups;
- adjust indentation and add blank lines as needed;
- adjust tables to match ReST accepted formats;
- use :field: markups;
- mark code blocks as such.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
