[RFC] Add support for KVM_GET_XSAVE2 ioctls
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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]>
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cc @likebreath since iirc you were looking into a post-5.17 solution for kvm_xsave, too |
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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
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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.