[RFC] Add support for KVM_GET_XSAVE2 ioctls
#261
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
roypat
requested review from
acatangiu,
alxiord,
andreeaflorescu,
lauralt,
sameo and
JonathanWoollett-Light
as code owners
roypat
force-pushed
the
kvm_get_xsave2
branch
5 times, most recently
from
1422be7 to
d9a5bf6
Compare
Since Linux 5.17, the `kvm_xsave` struct has a flexible array member (FAM) at the end, which can be retrieved using the `KVM_GET_XSAVE2` ioctl [1]. What makes this FAM special is that the length is not stored in the header, but has to be retrieved via `KVM_CHECK_CAPABILITY(KVM_CAP_XSAVE2)`, which returns the total size of the `kvm_xsave` struct (e.g. the traditional 4096 byte header + the size of the FAM). Thus, to support `KVM_GET_XSAVE2`, we first need to check the capability on the VM fd, construct a FamStructWrapper of the correct size, and then call `KVM_GET_XSAVE2`. [1]: https://www.kernel.org/doc/html/latest/virt/kvm/api.html#kvm-get-xsave2 Signed-off-by: Patrick Roy <[email protected]>
|
cc @likebreath since iirc you were looking into a post-5.17 solution for kvm_xsave, too |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Since Linux 5.17, the
kvm_xsavestruct has a flexible array member (FAM) at the end, which can be retrieved using theKVM_GET_XSAVE2ioctl [1]. What makes this FAM special is that the length is not stored in the header, but has to be retrieved viaKVM_CHECK_CAPABILITY(KVM_CAP_XSAVE2), which returns the total size of thekvm_xsavestruct (e.g. the traditional 4096 byte header + the size of the FAM). Thus, to supportKVM_GET_XSAVE2, we first need to check the capability on the VM fd, construct a FamStructWrapper of the correct size, and then callKVM_GET_XSAVE2.I'm marking this as "RFC" because I'm not quite sure how to best deal the combination of "check capability on VM FD" and "do ioctl on vcpu FD". In this patch, I simply add a
VmFdparameter toVcpu::get_xsave2, but that's kinda ugly. Alternatively, we could store a reference to the VM file descriptor inside eachVcpustructure, but that'd be a larger change. What do people think about this?(also, this PR needs rust-vmm/kvm-bindings#104, because Rust apparently only type checks type aliases at use-sites instead of definition-site, meaning I did not notice that I forgot to implementDefaultforkvm_xsave2when working on the new kvm-bindings release. That's why the CI is failing here for now)Requirements
Before submitting your PR, please make sure you addressed the following
requirements:
git commit -s), and the commit message has max 60 characters for thesummary and max 75 characters for each description line.
test.
Release" section of CHANGELOG.md (if no such section exists, please create one).
unsafecode is properly documented.