diff options
Diffstat (limited to 'OvmfPkg/Library/VirtioLib/VirtioLib.c')
| -rw-r--r-- | OvmfPkg/Library/VirtioLib/VirtioLib.c | 82 |
1 files changed, 45 insertions, 37 deletions
diff --git a/OvmfPkg/Library/VirtioLib/VirtioLib.c b/OvmfPkg/Library/VirtioLib/VirtioLib.c index 8398c9db4..87797e10e 100644 --- a/OvmfPkg/Library/VirtioLib/VirtioLib.c +++ b/OvmfPkg/Library/VirtioLib/VirtioLib.c @@ -285,7 +285,7 @@ VirtioRingUninit ( The calling driver must be in VSTAT_DRIVER_OK state.
- @param[in out] Ring The virtio ring we intend to append descriptors to.
+ @param[in,out] Ring The virtio ring we intend to append descriptors to.
@param[out] Indices The DESC_INDICES structure to initialize.
@@ -306,8 +306,11 @@ VirtioPrepare ( //
// Prepare for virtio-0.9.5, 2.4.1 Supplying Buffers to the Device.
//
- Indices->HeadIdx = *Ring->Avail.Idx;
- Indices->NextAvailIdx = Indices->HeadIdx;
+ // Since we support only one in-flight descriptor chain, we can always build
+ // that chain starting at entry #0 of the descriptor table.
+ //
+ Indices->HeadDescIdx = 0;
+ Indices->NextDescIdx = Indices->HeadDescIdx;
}
@@ -315,9 +318,8 @@ VirtioPrepare ( Append a contiguous buffer for transmission / reception via the virtio ring.
- This function implements the following sections from virtio-0.9.5:
+ This function implements the following section from virtio-0.9.5:
- 2.4.1.1 Placing Buffers into the Descriptor Table
- - 2.4.1.2 Updating the Available Ring
Free space is taken as granted, since the individual drivers support only
synchronous requests and host side status is processed in lock-step with
@@ -327,31 +329,26 @@ VirtioPrepare ( The caller is responsible for initializing *Indices with VirtioPrepare()
first.
- @param[in out] Ring The virtio ring to append the buffer to, as a
- descriptor.
-
- @param [in] BufferPhysAddr (Guest pseudo-physical) start address of the
- transmit / receive buffer.
+ @param[in,out] Ring The virtio ring to append the buffer to, as a
+ descriptor.
- @param [in] BufferSize Number of bytes to transmit or receive.
+ @param[in] BufferPhysAddr (Guest pseudo-physical) start address of the
+ transmit / receive buffer.
- @param [in] Flags A bitmask of VRING_DESC_F_* flags. The caller
- computes this mask dependent on further buffers
- to append and transfer direction.
- VRING_DESC_F_INDIRECT is unsupported. The
- VRING_DESC.Next field is always set, but the
- host only interprets it dependent on
- VRING_DESC_F_NEXT.
+ @param[in] BufferSize Number of bytes to transmit or receive.
- In *Indices:
+ @param[in] Flags A bitmask of VRING_DESC_F_* flags. The caller
+ computes this mask dependent on further buffers to
+ append and transfer direction.
+ VRING_DESC_F_INDIRECT is unsupported. The
+ VRING_DESC.Next field is always set, but the host
+ only interprets it dependent on VRING_DESC_F_NEXT.
- @param [in] HeadIdx The index identifying the head buffer (first
- buffer appended) belonging to this same
- request.
-
- @param [in out] NextAvailIdx On input, the index identifying the next
- descriptor available to carry the buffer. On
- output, incremented by one, modulo 2^16.
+ @param[in,out] Indices Indices->HeadDescIdx is not accessed.
+ On input, Indices->NextDescIdx identifies the next
+ descriptor to carry the buffer. On output,
+ Indices->NextDescIdx is incremented by one, modulo
+ 2^16.
**/
VOID
@@ -366,29 +363,28 @@ VirtioAppendDesc ( {
volatile VRING_DESC *Desc;
- Desc = &Ring->Desc[Indices->NextAvailIdx % Ring->QueueSize];
+ Desc = &Ring->Desc[Indices->NextDescIdx++ % Ring->QueueSize];
Desc->Addr = BufferPhysAddr;
Desc->Len = BufferSize;
Desc->Flags = Flags;
- Ring->Avail.Ring[Indices->NextAvailIdx++ % Ring->QueueSize] =
- Indices->HeadIdx % Ring->QueueSize;
- Desc->Next = Indices->NextAvailIdx % Ring->QueueSize;
+ Desc->Next = Indices->NextDescIdx % Ring->QueueSize;
}
/**
- Notify the host about appended descriptors and wait until it processes the
- last one (ie. all of them).
+ Notify the host about the descriptor chain just built, and wait until the
+ host processes it.
@param[in] PciIo The target virtio PCI device to notify.
@param[in] VirtQueueId Identifies the queue for the target device.
- @param[in out] Ring The virtio ring with descriptors to submit.
+ @param[in,out] Ring The virtio ring with descriptors to submit.
- @param[in] Indices The function waits until the host processes
- descriptors up to Indices->NextAvailIdx.
+ @param[in] Indices Indices->NextDescIdx is not accessed.
+ Indices->HeadDescIdx identifies the head descriptor
+ of the descriptor chain.
@return Error code from VirtioWrite() if it fails.
@@ -405,14 +401,26 @@ VirtioFlush ( IN DESC_INDICES *Indices
)
{
+ UINT16 NextAvailIdx;
EFI_STATUS Status;
UINTN PollPeriodUsecs;
//
+ // virtio-0.9.5, 2.4.1.2 Updating the Available Ring
+ //
+ // It is not exactly clear from the wording of the virtio-0.9.5
+ // specification, but each entry in the Available Ring references only the
+ // head descriptor of any given descriptor chain.
+ //
+ NextAvailIdx = *Ring->Avail.Idx;
+ Ring->Avail.Ring[NextAvailIdx++ % Ring->QueueSize] =
+ Indices->HeadDescIdx % Ring->QueueSize;
+
+ //
// virtio-0.9.5, 2.4.1.3 Updating the Index Field
//
MemoryFence();
- *Ring->Avail.Idx = Indices->NextAvailIdx;
+ *Ring->Avail.Idx = NextAvailIdx;
//
// virtio-0.9.5, 2.4.1.4 Notifying the Device -- gratuitous notifications are
@@ -439,7 +447,7 @@ VirtioFlush ( //
PollPeriodUsecs = 1;
MemoryFence();
- while (*Ring->Used.Idx != Indices->NextAvailIdx) {
+ while (*Ring->Used.Idx != NextAvailIdx) {
gBS->Stall (PollPeriodUsecs); // calls AcpiTimerLib::MicroSecondDelay
if (PollPeriodUsecs < 1024) {
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