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OvmfPkg: VirtioRngDxe: adapt feature negotiation to virtio-1.0 

Relative to virtio-0.9.5, virtio-1.0 reverses the order of queue discovery
and feature negotiation. In virtio-1.0, feature negotiation has to
complete first, and the device can also reject a self-inconsistent feature
request through the new VSTAT_FEATURES_OK status bit. (For example if the
driver requests a higher level feature but clears a prerequisite feature.)

Furthermore, we retain the VIRTIO_F_VERSION_1 feature bit if the
VIRTIO_DEVICE_PROTOCOL provider has high enough revision.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
This commit is contained in:
Laszlo Ersek 2016-03-12 14:41:26 +01:00
parent 33c6b934bf
commit 0a781bdc7f
1 changed files with 20 additions and 7 deletions
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21
OvmfPkg/VirtioRngDxe/VirtioRng.c
View File

@ -242,6 +242,19 @@ VirtioRngInit (
goto Failed;
}
Features &= VIRTIO_F_VERSION_1;
//
// In virtio-1.0, feature negotiation is expected to complete before queue
// discovery, and the device can also reject the selected set of features.
//
if (Dev->VirtIo->Revision >= VIRTIO_SPEC_REVISION (1, 0, 0)) {
Status = Virtio10WriteFeatures (Dev->VirtIo, Features, &NextDevStat);
if (EFI_ERROR (Status)) {
goto Failed;
}
}
//
// step 4b -- allocate request virtqueue, just use #0
//
@ -290,15 +303,15 @@ VirtioRngInit (
}
//
// step 5 -- Report understood features and guest-tuneables. None are
// currently defined for VirtioRng, and no generic features are needed by
// this driver.
// step 5 -- Report understood features and guest-tuneables.
//
Features &= 0;
if (Dev->VirtIo->Revision < VIRTIO_SPEC_REVISION (1, 0, 0)) {
Features &= ~(UINT64)VIRTIO_F_VERSION_1;
Status = Dev->VirtIo->SetGuestFeatures (Dev->VirtIo, Features);
if (EFI_ERROR (Status)) {
goto ReleaseQueue;
}
}
//
// step 6 -- initialization complete