UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

KVM: Document the interaction between KVM_CAP_HALT_POLL and halt_poll_ns 

Clarify the existing documentation about how KVM_CAP_HALT_POLL and
halt_poll_ns interact to make it clear that VMs using KVM_CAP_HALT_POLL
ignore halt_poll_ns.

Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20221201195249.3369720-3-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Matlack 2022-12-01 11:52:49 -08:00 committed by Paolo Bonzini
parent b8b43a4c2e
commit 34e30ebbe4
2 changed files with 19 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
Documentation/virt/kvm/api.rst
View File

@ -7213,14 +7213,13 @@ veto the transition.
:Parameters: args[0] is the maximum poll time in nanoseconds
:Returns: 0 on success; -1 on error
This capability overrides the kvm module parameter halt_poll_ns for the
target VM.
KVM_CAP_HALT_POLL overrides the kvm.halt_poll_ns module parameter to set the
maximum halt-polling time for all vCPUs in the target VM. This capability can
be invoked at any time and any number of times to dynamically change the
maximum halt-polling time.
VCPU polling allows a VCPU to poll for wakeup events instead of immediately
scheduling during guest halts. The maximum time a VCPU can spend polling is
controlled by the kvm module parameter halt_poll_ns. This capability allows
the maximum halt time to specified on a per-VM basis, effectively overriding
the module parameter for the target VM.
See Documentation/virt/kvm/halt-polling.rst for more information on halt
polling.
7.21 KVM_CAP_X86_USER_SPACE_MSR
-------------------------------

13
Documentation/virt/kvm/halt-polling.rst
View File

@ -119,6 +119,19 @@ These module parameters can be set from the debugfs files in:
Note: that these module parameters are system wide values and are not able to
be tuned on a per vm basis.
Any changes to these parameters will be picked up by new and existing vCPUs the
next time they halt, with the notable exception of VMs using KVM_CAP_HALT_POLL
(see next section).
KVM_CAP_HALT_POLL
=================
KVM_CAP_HALT_POLL is a VM capability that allows userspace to override halt_poll_ns
on a per-VM basis. VMs using KVM_CAP_HALT_POLL ignore halt_poll_ns completely (but
still obey halt_poll_ns_grow, halt_poll_ns_grow_start, and halt_poll_ns_shrink).
See Documentation/virt/kvm/api.rst for more information on this capability.
Further Notes
=============