Messages in this thread | | | Date | Tue, 21 Dec 2021 09:45:24 +0100 | Subject | Re: [PATCH v2 18/23] kvm: x86: Get/set expanded xstate buffer | From | Paolo Bonzini <> |
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On 12/21/21 03:45, Wang, Wei W wrote: >> KVM_GET_XSAVE2 and KVM_SET_XSAVE respectively write and read as many >> bytes as are returned by KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2), when >> invoked on the vm file descriptor. Currently, >> KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) will only return a value that is >> greater than 4096 bytes if any dynamic features have been enabled with >> ``arch_prctl()``; this however may change in the future. > Would this make people think that KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) doesn’t > return the value (i.e. return 0) if it is smaller than 4096? > (i.e. KVM_GET_XSAVE2 doesn't work with size < 4096, which isn’t true) > > I plan to just reword a bit: > Currently, KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) will only return a size value, > and the value is greater than 4096 bytes if any dynamic features have been enabled with > ``arch_prctl()``. More types of values could be returned in the future.
Next refinement:
The size value returned by KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) will always be at least 4096. Currently, it is only greater than 4096 if a dynamic feature has been enabled with ``arch_prctl()``, but this may change in the future.
(I'm not sure if the first sentence is true in the code, but if not it is a bug that has to be fixed :)).
Paolo
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