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KVM: x86/xen: Documentation updates and clarifications

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Most notably, the KVM_XEN_EVTCHN_RESET feature had escaped documentation
entirely. Along with how to turn most stuff off on SHUTDOWN_soft_reset.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20221226120320.1125390-6-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Woodhouse 2022-12-26 12:03:20 +00:00 committed by Paolo Bonzini
parent b0305c1e0e
commit af2808906a
1 changed files with 26 additions and 15 deletions
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41
Documentation/virt/kvm/api.rst
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@ -5343,9 +5343,9 @@ KVM_XEN_ATTR_TYPE_SHARED_INFO
32 vCPUs in the shared_info page, KVM does not automatically do so
and instead requires that KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO be used
explicitly even when the vcpu_info for a given vCPU resides at the
"default" location in the shared_info page. This is because KVM is
not aware of the Xen CPU id which is used as the index into the
vcpu_info[] array, so cannot know the correct default location.
"default" location in the shared_info page. This is because KVM may
not be aware of the Xen CPU id which is used as the index into the
vcpu_info[] array, so may know the correct default location.
Note that the shared info page may be constantly written to by KVM;
it contains the event channel bitmap used to deliver interrupts to
@ -5356,23 +5356,29 @@ KVM_XEN_ATTR_TYPE_SHARED_INFO
any vCPU has been running or any event channel interrupts can be
routed to the guest.
Setting the gfn to KVM_XEN_INVALID_GFN will disable the shared info
page.
KVM_XEN_ATTR_TYPE_UPCALL_VECTOR
Sets the exception vector used to deliver Xen event channel upcalls.
This is the HVM-wide vector injected directly by the hypervisor
(not through the local APIC), typically configured by a guest via
HVM_PARAM_CALLBACK_IRQ.
HVM_PARAM_CALLBACK_IRQ. This can be disabled again (e.g. for guest
SHUTDOWN_soft_reset) by setting it to zero.
KVM_XEN_ATTR_TYPE_EVTCHN
This attribute is available when the KVM_CAP_XEN_HVM ioctl indicates
support for KVM_XEN_HVM_CONFIG_EVTCHN_SEND features. It configures
an outbound port number for interception of EVTCHNOP_send requests
from the guest. A given sending port number may be directed back
to a specified vCPU (by APIC ID) / port / priority on the guest,
or to trigger events on an eventfd. The vCPU and priority can be
changed by setting KVM_XEN_EVTCHN_UPDATE in a subsequent call,
but other fields cannot change for a given sending port. A port
mapping is removed by using KVM_XEN_EVTCHN_DEASSIGN in the flags
field.
from the guest. A given sending port number may be directed back to
a specified vCPU (by APIC ID) / port / priority on the guest, or to
trigger events on an eventfd. The vCPU and priority can be changed
by setting KVM_XEN_EVTCHN_UPDATE in a subsequent call, but but other
fields cannot change for a given sending port. A port mapping is
removed by using KVM_XEN_EVTCHN_DEASSIGN in the flags field. Passing
KVM_XEN_EVTCHN_RESET in the flags field removes all interception of
outbound event channels. The values of the flags field are mutually
exclusive and cannot be combined as a bitmask.
KVM_XEN_ATTR_TYPE_XEN_VERSION
This attribute is available when the KVM_CAP_XEN_HVM ioctl indicates
@ -5388,7 +5394,7 @@ KVM_XEN_ATTR_TYPE_RUNSTATE_UPDATE_FLAG
support for KVM_XEN_HVM_CONFIG_RUNSTATE_UPDATE_FLAG. It enables the
XEN_RUNSTATE_UPDATE flag which allows guest vCPUs to safely read
other vCPUs' vcpu_runstate_info. Xen guests enable this feature via
the VM_ASST_TYPE_runstate_update_flag of the HYPERVISOR_vm_assist
the VMASST_TYPE_runstate_update_flag of the HYPERVISOR_vm_assist
hypercall.
4.127 KVM_XEN_HVM_GET_ATTR
@ -5446,15 +5452,18 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO
As with the shared_info page for the VM, the corresponding page may be
dirtied at any time if event channel interrupt delivery is enabled, so
userspace should always assume that the page is dirty without relying
on dirty logging.
on dirty logging. Setting the gpa to KVM_XEN_INVALID_GPA will disable
the vcpu_info.
KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
Sets the guest physical address of an additional pvclock structure
for a given vCPU. This is typically used for guest vsyscall support.
Setting the gpa to KVM_XEN_INVALID_GPA will disable the structure.
KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR
Sets the guest physical address of the vcpu_runstate_info for a given
vCPU. This is how a Xen guest tracks CPU state such as steal time.
Setting the gpa to KVM_XEN_INVALID_GPA will disable the runstate area.
KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT
Sets the runstate (RUNSTATE_running/_runnable/_blocked/_offline) of
@ -5487,7 +5496,8 @@ KVM_XEN_VCPU_ATTR_TYPE_TIMER
This attribute is available when the KVM_CAP_XEN_HVM ioctl indicates
support for KVM_XEN_HVM_CONFIG_EVTCHN_SEND features. It sets the
event channel port/priority for the VIRQ_TIMER of the vCPU, as well
as allowing a pending timer to be saved/restored.
as allowing a pending timer to be saved/restored. Setting the timer
port to zero disables kernel handling of the singleshot timer.
KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR
This attribute is available when the KVM_CAP_XEN_HVM ioctl indicates
@ -5495,7 +5505,8 @@ KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR
per-vCPU local APIC upcall vector, configured by a Xen guest with
the HVMOP_set_evtchn_upcall_vector hypercall. This is typically
used by Windows guests, and is distinct from the HVM-wide upcall
vector configured with HVM_PARAM_CALLBACK_IRQ.
vector configured with HVM_PARAM_CALLBACK_IRQ. It is disabled by
setting the vector to zero.
4.129 KVM_XEN_VCPU_GET_ATTR