Messages in this thread | | | Date | Tue, 14 Dec 2021 07:18:57 +0100 | Subject | Re: [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl | From | Paolo Bonzini <> |
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On 12/14/21 07:06, Wang, Wei W wrote: > On Monday, December 13, 2021 5:24 PM, Paolo Bonzini wrote: >> There is no need for struct kvm_xsave2, because there is no need for a "size" >> argument. >> >> - KVM_GET_XSAVE2 *is* needed, and it can expect a buffer as big as the return >> value of KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) > > Why would KVM_GET_XSAVE2 still be needed in this case? > > I'm thinking it would also be possible to reuse KVM_GET_XSAVE: > > - If userspace calls to KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2), > then KVM knows that the userspace is a new version and it works with larger xsave buffer using the "size" that it returns via KVM_CAP_XSAVE2. > So we can add a flag "kvm->xsave2_enabled", which gets set upon userspace checks KVM_CAP_XSAVE2.
You can use KVM_ENABLE_CAP(KVM_CAP_XSAVE2) for that, yes. In that case you don't need KVM_GET_XSAVE2.
Paolo
> - On KVM_GET_XSAVE, if "kvm->xsave2_enabled" is set, > then KVM allocates buffer to load xstates and copies the loaded xstates data to the userspace buffer > using the "size" that was returned to userspace on KVM_CAP_XSAVE2. > If "kvm->xsave2_enabled" isn't set, using the legacy "4KB" size. > > Thanks, > Wei >
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