On 10/13/21 2:20 PM, Sean Christopherson wrote:

On Fri, Aug 20, 2021, Brijesh Singh wrote:

quoted

The setup_vmgexit_scratch() function may rely on a long-lived GHCB
mapping if the GHCB shared buffer area was used for the scratch area.
In preparation for eliminating the long-lived GHCB mapping, always
allocate a buffer for the scratch area so it can be accessed without
the GHCB mapping.

Would it make sense to post this patch and the next (Remove the long-lived GHCB
host map) in a separate mini-series?  It's needed for SNP, but AFAICT there's
nothing that depends on SNP.  Getting this merged ahead of time would reduce the
size of the SNP series by a smidge.

While testing with random configs, I am seeing some might_sleep() warns.
This is happening mainly because during the vmrun the GHCB is accessed
with preempt disabled. The kvm_vcpu_map() -> kmap() reports the warning.
I am leaning towards creating a cache on the vmgexit and use that cache
instead of the doing a kmap() on every access. Does that sound okay to you ?

-Brijesh