Messages in this thread | | | From | Peter Gonda <> | Date | Mon, 7 Nov 2022 10:24:23 -0700 | Subject | Re: [PATCH v8 4/4] virt: sev-guest: interpret VMM errors from guest request |
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On Fri, Nov 4, 2022 at 7:33 PM Peter Gonda <pgonda@google.com> wrote: > > On Fri, Nov 4, 2022 at 5:01 PM Dionna Glaze <dionnaglaze@google.com> wrote: > > > > The GHCB specification states that the upper 32 bits of exitinfo2 are > > for the VMM's error codes. The sev-guest ABI has already locked in > > that the fw_err status of the input will be 64 bits, and that > > BIT_ULL(32) means that the extended guest request's data buffer was too > > small, so we have to keep that ABI. > > > > We can still interpret the upper 32 bits of exitinfo2 for the user > > anyway in case the request gets throttled. For safety, since the > > encryption algorithm in GHCBv2 is AES_GCM, we cannot return to user > > space without having completed the request with the current sequence > > number. If we were to return and the guest were to make another request > > but with different message contents, then that would be IV reuse. > > > > When throttled, the driver will reschedule itself and then try > > again after sleeping half its ratelimit time to avoid a big wait queue. > > The ioctl may block indefinitely, but that has always been the case > > when deferring these requests to the host. > > > > Cc: Tom Lendacky <Thomas.Lendacky@amd.com> > > Cc: Peter Gonda <pgonda@google.com> > > Cc: Borislav Petkov <bp@suse.de> > > Cc: Tom Lendacky <thomas.lendacky@amd.com> > > Cc: Liam Merwick <liam.merwick@oracle.com> > > Cc: Yang Yingliang <yangyingliang@huawei.com> > > Cc: Haowen Bai <baihaowen@meizu.com> > > > > Signed-off-by: Dionna Glaze <dionnaglaze@google.com> > > Reviewed-by: Peter Gonda <pgonda@google.com>
Tested-by: Peter Gonda <pgonda@google.com>
Tested with the host throttling patches you shared offlist. Used a pretty restrictive rate limit to ensure I the hit the limit during testing.
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