Re: [Xen-devel] [PATCH v3 1/2] SVM: re-work VMCB sync-ing

[Juergen Gross <jgross@xxxxxxxx>]

On 04/05/18 17:10, Jan Beulich wrote:
> While the main problem to be addressed here is the issue of what so far
> was named "vmcb_in_sync" starting out with the wrong value (should have
> been true instead of false, to prevent performing a VMSAVE without ever
> having VMLOADed the vCPU's state), go a step further and make the
> sync-ed state a tristate: CPU and memory may be in sync or an update
> may be required in either direction. Rename the field and introduce an
> enum. Callers of svm_sync_vmcb() now indicate the intended new state
> (with a slight "anomaly" when requesting VMLOAD: we could store
> vmcb_needs_vmsave in those cases as the callers request, but the VMCB
> really is in sync at that point, and hence there's no need to VMSAVE in
> case we don't make it out to guest context), and all syncing goes
> through that function.
> 
> With that, there's no need to VMLOAD the state perhaps multiple times;
> all that's needed is loading it once before VM entry.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Release-acked-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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