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As long as we had purely EL1 VMs, we could easily update the number
of guest-visible counters by letting userspace write to PMCR_EL0.N.
With VMs started at EL2, PMCR_EL1.N only reflects MDCR_EL2.HPMN,
and we don't have a good way to limit it.
For this purpose, introduce a new PMUv3 attribute that allows
limiting the maximum number of counters. This requires the explicit
selection of a PMU.
Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
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Stephen reports that 'make htmldocs' spits out a warning
("Documentation/virt/kvm/devices/vcpu.rst:147: WARNING: Definition
list ends without a blank line; unexpected unindent.").
Fix it by keeping all the timer attributes on a single line.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Marc Zyngier <maz@kernel.org>
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Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241217142321.763801-13-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
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This includes table format and using reST labels for
cross-referencing to vcpu.rst.
Suggested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Usama Arif <usama.arif@bytedance.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221103131210.3603385-1-usama.arif@bytedance.com
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* kvm-arm64/misc-5.18:
: .
: Misc fixes for KVM/arm64 5.18:
:
: - Drop unused kvm parameter to kvm_psci_version()
:
: - Implement CONFIG_DEBUG_LIST at EL2
:
: - Make CONFIG_ARM64_ERRATUM_2077057 default y
:
: - Only do the interrupt dance if we have exited because of an interrupt
:
: - Remove traces of 32bit ARM host support from the documentation
: .
Documentation: KVM: Update documentation to indicate KVM is arm64-only
KVM: arm64: Only open the interrupt window on exit due to an interrupt
KVM: arm64: Enable Cortex-A510 erratum 2077057 by default
Signed-off-by: Marc Zyngier <maz@kernel.org>
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KVM support for 32-bit ARM hosts (KVM/arm) has been removed from the
kernel since commit 541ad0150ca4 ("arm: Remove 32bit KVM host
support"). There still exists some remnants of the old architecture in
the KVM documentation.
Remove all traces of 32-bit host support from the documentation. Note
that AArch32 guests are still supported.
Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220308172856.2997250-1-oupton@google.com
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Userspace can assign a PMU to a VCPU with the KVM_ARM_VCPU_PMU_V3_SET_PMU
device ioctl. If the VCPU is scheduled on a physical CPU which has a
different PMU, the perf events needed to emulate a guest PMU won't be
scheduled in and the guest performance counters will stop counting. Treat
it as an userspace error and refuse to run the VCPU in this situation.
Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220127161759.53553-7-alexandru.elisei@arm.com
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When KVM creates an event and there are more than one PMUs present on the
system, perf_init_event() will go through the list of available PMUs and
will choose the first one that can create the event. The order of the PMUs
in this list depends on the probe order, which can change under various
circumstances, for example if the order of the PMU nodes change in the DTB
or if asynchronous driver probing is enabled on the kernel command line
(with the driver_async_probe=armv8-pmu option).
Another consequence of this approach is that on heteregeneous systems all
virtual machines that KVM creates will use the same PMU. This might cause
unexpected behaviour for userspace: when a VCPU is executing on the
physical CPU that uses this default PMU, PMU events in the guest work
correctly; but when the same VCPU executes on another CPU, PMU events in
the guest will suddenly stop counting.
Fortunately, perf core allows user to specify on which PMU to create an
event by using the perf_event_attr->type field, which is used by
perf_init_event() as an index in the radix tree of available PMUs.
Add the KVM_ARM_VCPU_PMU_V3_CTRL(KVM_ARM_VCPU_PMU_V3_SET_PMU) VCPU
attribute to allow userspace to specify the arm_pmu that KVM will use when
creating events for that VCPU. KVM will make no attempt to run the VCPU on
the physical CPUs that share the PMU, leaving it up to userspace to manage
the VCPU threads' affinity accordingly.
To ensure that KVM doesn't expose an asymmetric system to the guest, the
PMU set for one VCPU will be used by all other VCPUs. Once a VCPU has run,
the PMU cannot be changed in order to avoid changing the list of available
events for a VCPU, or to change the semantics of existing events.
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220127161759.53553-6-alexandru.elisei@arm.com
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Userspace can specify which events a guest is allowed to use with the
KVM_ARM_VCPU_PMU_V3_FILTER attribute. The list of allowed events can be
identified by a guest from reading the PMCEID{0,1}_EL0 registers.
Changing the PMU event filter after a VCPU has run can cause reads of the
registers performed before the filter is changed to return different values
than reads performed with the new event filter in place. The architecture
defines the two registers as read-only, and this behaviour contradicts
that.
Keep track when the first VCPU has run and deny changes to the PMU event
filter to prevent this from happening.
Signed-off-by: Marc Zyngier <maz@kernel.org>
[ Alexandru E: Added commit message, updated ioctl documentation ]
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220127161759.53553-2-alexandru.elisei@arm.com
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Introduce a KVM selftest to verify that userspace manipulation of the
TSC (via the new vCPU attribute) results in the correct behavior within
the guest.
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Message-Id: <20210916181555.973085-6-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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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>
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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: 8be86a5eec04 ("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
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Update the description of the PMU KVM_{GET, SET}_DEVICE_ATTR error codes
to be a better match for the code that returns them.
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/20200924123731.268177-3-alexandru.elisei@arm.com
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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
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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>
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Several references got broken due to txt to ReST conversion.
Several of them can be automatically fixed with:
scripts/documentation-file-ref-check --fix
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org> # hwtracing/coresight/Kconfig
Reviewed-by: Paul E. McKenney <paulmck@kernel.org> # memory-barrier.txt
Acked-by: Alex Shi <alex.shi@linux.alibaba.com> # translations/zh_CN
Acked-by: Federico Vaga <federico.vaga@vaga.pv.it> # translations/it_IT
Acked-by: Marc Zyngier <maz@kernel.org> # kvm/arm64
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/6f919ddb83a33b5f2a63b6b5f0575737bb2b36aa.1586881715.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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- 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>
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