OvmfPkg/XenPvBlkDxe: Add BlockFront client.

This is the code that will do the actual communication between OVMF and
a PV block backend, where the block device lives. The protocol used is
describe in the blkif.h header.

This implementation originally comes from Mini-OS, a part of the Xen
Project.

Change in V4:
- add file header to BlockFront.h (license, copyright, brief desc)

Change in V3:
- Improve comment of XenBusReadUint64.
- Moving blkif.h to this patch
  with the necessary #pragma pack(4) applied for Ia32.
- Add a note about the license in the commit message
- Add "The protocol used is describe in the blkif.h header." in the
  commit message
- Have a mandatory sector-size multiple of 512 or fail to initialize.
- use Sector instead of Offset for IO request.
  with Sector been 512-byte unit.
- print something if EventChannelNotify return an error.

Change in V2:
- trigger CoW is probably not needed on OVMF (as opposed to Mini-OS),
  removed the test.
- comments
- renamed XenbusReadInteger to XenBusReadUint64
- remove callback from IoData, use simple status instead
- return a status from the synchronus io
- Close protocol if blockfront init fail.
- fix few debug print
- Rename XenbusIo to XenBusIo
- XenPvBlkWaitForBackendState will return an error if the new backend
  states is not the expected state.
- Add the license

License: This patch adds some files which are under the MIT license.
Signed-off-by: Samuel Thibault <samuel.thibault@eu.citrix.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16273 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 647 insertions, 0 deletions

diff --git a/OvmfPkg/XenPvBlkDxe/BlockFront.c b/OvmfPkg/XenPvBlkDxe/BlockFront.c
new file mode 100644
index 0000000000..3c039e7add
--- /dev/null
+++ b/OvmfPkg/XenPvBlkDxe/BlockFront.c
@@ -0,0 +1,647 @@
+/** @file

+  Minimal block driver for Mini-OS.

+

+  Copyright (c) 2007-2008 Samuel Thibault.

+  Copyright (C) 2014, Citrix Ltd.

+

+  Redistribution and use in source and binary forms, with or without

+  modification, are permitted provided that the following conditions

+  are met:

+  1. Redistributions of source code must retain the above copyright

+     notice, this list of conditions and the following disclaimer.

+  2. Redistributions in binary form must reproduce the above copyright

+     notice, this list of conditions and the following disclaimer in the

+     documentation and/or other materials provided with the distribution.

+

+  THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND

+  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

+  ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE

+  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

+  OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

+  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

+  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

+  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

+  SUCH DAMAGE.

+**/

+

+#include <Library/PrintLib.h>

+#include <Library/DebugLib.h>

+

+#include "BlockFront.h"

+

+#include <IndustryStandard/Xen/io/protocols.h>

+#include <IndustryStandard/Xen/io/xenbus.h>

+

+//

+// Header used for UINT32_MAX and UINT16_MAX

+//

+#include "inttypes.h"

+

+/**

+  Helper to read an integer from XenStore.

+

+  If the number overflows according to the range defined by UINT64,

+  then ASSERT().

+

+  @param This         A pointer to a XENBUS_PROTOCOL instance.

+  @param Node         The XenStore node to read from.

+  @param FromBackend  Read frontend or backend value.

+  @param ValuePtr     Where to put the value.

+

+  @retval XENSTORE_STATUS_SUCCESS  If succefull, will update ValuePtr.

+  @return                          Any other return value indicate the error,

+                                   ValuePtr is not updated in this case.

+**/

+STATIC

+XENSTORE_STATUS

+XenBusReadUint64 (

+  IN  XENBUS_PROTOCOL *This,

+  IN  CONST CHAR8     *Node,

+  IN  BOOLEAN         FromBackend,

+  OUT UINT64          *ValuePtr

+  )

+{

+  XENSTORE_STATUS Status;

+  CHAR8 *Ptr;

+

+  if (!FromBackend) {

+    Status = This->XsRead (This, XST_NIL, Node, (VOID**)&Ptr);

+  } else {

+    Status = This->XsBackendRead (This, XST_NIL, Node, (VOID**)&Ptr);

+  }

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    return Status;

+  }

+  // AsciiStrDecimalToUint64 will ASSERT if Ptr overflow UINT64.

+  *ValuePtr = AsciiStrDecimalToUint64 (Ptr);

+  FreePool (Ptr);

+  return Status;

+}

+

+/**

+  Free an instance of XEN_BLOCK_FRONT_DEVICE.

+

+  @param Dev  The instance to free.

+**/

+STATIC

+VOID

+XenPvBlockFree (

+  IN XEN_BLOCK_FRONT_DEVICE *Dev

+  )

+{

+  XENBUS_PROTOCOL *XenBusIo = Dev->XenBusIo;

+

+  if (Dev->RingRef != 0) {

+    XenBusIo->GrantEndAccess (XenBusIo, Dev->RingRef);

+  }

+  if (Dev->Ring.sring != NULL) {

+    FreePages (Dev->Ring.sring, 1);

+  }

+  if (Dev->EventChannel != 0) {

+    XenBusIo->EventChannelClose (XenBusIo, Dev->EventChannel);

+  }

+  FreePool (Dev);

+}

+

+/**

+  Wait until until the backend has reached the ExpectedState.

+

+  @param Dev            A XEN_BLOCK_FRONT_DEVICE instance.

+  @param ExpectedState  The backend state expected.

+  @param LastStatePtr   An optional pointer where to right the final state.

+

+  @return Return XENSTORE_STATUS_SUCCESS if the new backend state is ExpectedState

+          or return an error otherwise.

+**/

+STATIC

+XENSTORE_STATUS

+XenPvBlkWaitForBackendState (

+  IN  XEN_BLOCK_FRONT_DEVICE *Dev,

+  IN  XenbusState            ExpectedState,

+  OUT XenbusState            *LastStatePtr OPTIONAL

+  )

+{

+  XENBUS_PROTOCOL *XenBusIo = Dev->XenBusIo;

+  XenbusState State;

+  UINT64 Value;

+  XENSTORE_STATUS Status = XENSTORE_STATUS_SUCCESS;

+

+  while (TRUE) {

+    Status = XenBusReadUint64 (XenBusIo, "state", TRUE, &Value);

+    if (Status != XENSTORE_STATUS_SUCCESS) {

+      return Status;

+    }

+    if (Value > XenbusStateReconfigured) {

+      //

+      // Value is not a State value.

+      //

+      return XENSTORE_STATUS_EIO;

+    }

+    State = Value;

+    if (State == ExpectedState) {

+      break;

+    } else if (State > ExpectedState) {

+      Status = XENSTORE_STATUS_FAIL;

+      break;

+    }

+    DEBUG ((EFI_D_INFO,

+            "XenPvBlk: waiting backend state %d, current: %d\n",

+            ExpectedState, State));

+    XenBusIo->WaitForWatch (XenBusIo, Dev->StateWatchToken);

+  }

+

+  if (LastStatePtr != NULL) {

+    *LastStatePtr = State;

+  }

+

+  return Status;

+}

+

+EFI_STATUS

+XenPvBlockFrontInitialization (

+  IN  XENBUS_PROTOCOL         *XenBusIo,

+  IN  CONST CHAR8             *NodeName,

+  OUT XEN_BLOCK_FRONT_DEVICE  **DevPtr

+  )

+{

+  XENSTORE_TRANSACTION xbt;

+  CHAR8 *DeviceType;

+  blkif_sring_t *SharedRing;

+  XENSTORE_STATUS Status;

+  XEN_BLOCK_FRONT_DEVICE *Dev;

+  XenbusState State;

+  UINT64 Value;

+

+  ASSERT (NodeName != NULL);

+

+  Dev = AllocateZeroPool (sizeof (XEN_BLOCK_FRONT_DEVICE));

+  Dev->Signature = XEN_BLOCK_FRONT_SIGNATURE;

+  Dev->NodeName = NodeName;

+  Dev->XenBusIo = XenBusIo;

+  Dev->DeviceId = XenBusIo->DeviceId;

+

+  XenBusIo->XsRead (XenBusIo, XST_NIL, "device-type", (VOID**)&DeviceType);

+  if (AsciiStrCmp (DeviceType, "cdrom") == 0) {

+    Dev->MediaInfo.CdRom = TRUE;

+  } else {

+    Dev->MediaInfo.CdRom = FALSE;

+  }

+  FreePool (DeviceType);

+

+  Status = XenBusReadUint64 (XenBusIo, "backend-id", FALSE, &Value);

+  if (Status != XENSTORE_STATUS_SUCCESS || Value > UINT16_MAX) {

+    DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to get backend-id (%d)\n",

+            Status));

+    goto Error;

+  }

+  Dev->DomainId = Value;

+  XenBusIo->EventChannelAllocate (XenBusIo, Dev->DomainId, &Dev->EventChannel);

+

+  SharedRing = (blkif_sring_t*) AllocatePages (1);

+  SHARED_RING_INIT (SharedRing);

+  FRONT_RING_INIT (&Dev->Ring, SharedRing, EFI_PAGE_SIZE);

+  XenBusIo->GrantAccess (XenBusIo,

+                         Dev->DomainId,

+                         (INTN) SharedRing >> EFI_PAGE_SHIFT,

+                         FALSE,

+                         &Dev->RingRef);

+

+Again:

+  Status = XenBusIo->XsTransactionStart (XenBusIo, &xbt);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_WARN, "XenPvBlk: Failed to start transaction, %d\n", Status));

+    goto Error;

+  }

+

+  Status = XenBusIo->XsPrintf (XenBusIo, xbt, NodeName, "ring-ref", "%d",

+                               Dev->RingRef);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to write ring-ref.\n"));

+    goto AbortTransaction;

+  }

+  Status = XenBusIo->XsPrintf (XenBusIo, xbt, NodeName,

+                               "event-channel", "%d", Dev->EventChannel);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to write event-channel.\n"));

+    goto AbortTransaction;

+  }

+  Status = XenBusIo->XsPrintf (XenBusIo, xbt, NodeName,

+                               "protocol", "%a", XEN_IO_PROTO_ABI_NATIVE);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to write protocol.\n"));

+    goto AbortTransaction;

+  }

+

+  Status = XenBusIo->SetState (XenBusIo, xbt, XenbusStateConnected);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR, "XenPvBlk: Failed to switch state.\n"));

+    goto AbortTransaction;

+  }

+

+  Status = XenBusIo->XsTransactionEnd (XenBusIo, xbt, FALSE);

+  if (Status == XENSTORE_STATUS_EAGAIN) {

+    goto Again;

+  }

+

+  XenBusIo->RegisterWatchBackend (XenBusIo, "state", &Dev->StateWatchToken);

+

+  //

+  // Waiting for backend

+  //

+  Status = XenPvBlkWaitForBackendState (Dev, XenbusStateConnected, &State);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR,

+            "XenPvBlk: backend for %a/%d not available, rc=%d state=%d\n",

+            XenBusIo->Type, XenBusIo->DeviceId, Status, State));

+    goto Error2;

+  }

+

+  Status = XenBusReadUint64 (XenBusIo, "info", TRUE, &Value);

+  if (Status != XENSTORE_STATUS_SUCCESS || Value > UINT32_MAX) {

+    goto Error2;

+  }

+  Dev->MediaInfo.VDiskInfo = Value;

+  if (Dev->MediaInfo.VDiskInfo & VDISK_READONLY) {

+    Dev->MediaInfo.ReadWrite = FALSE;

+  } else {

+    Dev->MediaInfo.ReadWrite = TRUE;

+  }

+

+  Status = XenBusReadUint64 (XenBusIo, "sectors", TRUE, &Dev->MediaInfo.Sectors);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    goto Error2;

+  }

+

+  Status = XenBusReadUint64 (XenBusIo, "sector-size", TRUE, &Value);

+  if (Status != XENSTORE_STATUS_SUCCESS || Value > UINT32_MAX) {

+    goto Error2;

+  }

+  if (Value % 512 != 0) {

+    //

+    // This is not supported by the driver.

+    //

+    DEBUG ((EFI_D_ERROR, "XenPvBlk: Unsupported sector-size value %d, "

+            "it must be a multiple of 512\n", Value));

+    goto Error2;

+  }

+  Dev->MediaInfo.SectorSize = Value;

+

+  // Default value

+  Value = 0;

+  XenBusReadUint64 (XenBusIo, "feature-barrier", TRUE, &Value);

+  if (Value == 1) {

+    Dev->MediaInfo.FeatureBarrier = TRUE;

+  } else {

+    Dev->MediaInfo.FeatureBarrier = FALSE;

+  }

+

+  // Default value

+  Value = 0;

+  XenBusReadUint64 (XenBusIo, "feature-flush-cache", TRUE, &Value);

+  if (Value == 1) {

+    Dev->MediaInfo.FeatureFlushCache = TRUE;

+  } else {

+    Dev->MediaInfo.FeatureFlushCache = FALSE;

+  }

+

+  DEBUG ((EFI_D_INFO, "XenPvBlk: New disk with %ld sectors of %d bytes\n",

+          Dev->MediaInfo.Sectors, Dev->MediaInfo.SectorSize));

+

+  *DevPtr = Dev;

+  return EFI_SUCCESS;

+

+Error2:

+  XenBusIo->UnregisterWatch (XenBusIo, Dev->StateWatchToken);

+  XenBusIo->XsRemove (XenBusIo, XST_NIL, "ring-ref");

+  XenBusIo->XsRemove (XenBusIo, XST_NIL, "event-channel");

+  XenBusIo->XsRemove (XenBusIo, XST_NIL, "protocol");

+  goto Error;

+AbortTransaction:

+  XenBusIo->XsTransactionEnd (XenBusIo, xbt, TRUE);

+Error:

+  XenPvBlockFree (Dev);

+  return EFI_DEVICE_ERROR;

+}

+

+VOID

+XenPvBlockFrontShutdown (

+  IN XEN_BLOCK_FRONT_DEVICE *Dev

+  )

+{

+  XENBUS_PROTOCOL *XenBusIo = Dev->XenBusIo;

+  XENSTORE_STATUS Status;

+  UINT64 Value;

+

+  XenPvBlockSync (Dev);

+

+  Status = XenBusIo->SetState (XenBusIo, XST_NIL, XenbusStateClosing);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR,

+            "XenPvBlk: error while changing state to Closing: %d\n",

+            Status));

+    goto Close;

+  }

+

+  Status = XenPvBlkWaitForBackendState (Dev, XenbusStateClosing, NULL);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR,

+            "XenPvBlk: error while waiting for closing backend state: %d\n",

+            Status));

+    goto Close;

+  }

+

+  Status = XenBusIo->SetState (XenBusIo, XST_NIL, XenbusStateClosed);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR,

+            "XenPvBlk: error while changing state to Closed: %d\n",

+            Status));

+    goto Close;

+  }

+

+  Status = XenPvBlkWaitForBackendState (Dev, XenbusStateClosed, NULL);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR,

+            "XenPvBlk: error while waiting for closed backend state: %d\n",

+            Status));

+    goto Close;

+  }

+

+  Status = XenBusIo->SetState (XenBusIo, XST_NIL, XenbusStateInitialising);

+  if (Status != XENSTORE_STATUS_SUCCESS) {

+    DEBUG ((EFI_D_ERROR,

+            "XenPvBlk: error while changing state to initialising: %d\n",

+            Status));

+    goto Close;

+  }

+

+  while (TRUE) {

+    Status = XenBusReadUint64 (XenBusIo, "state", TRUE, &Value);

+    if (Status != XENSTORE_STATUS_SUCCESS) {

+      DEBUG ((EFI_D_ERROR,

+              "XenPvBlk: error while waiting for new backend state: %d\n",

+              Status));

+      goto Close;

+    }

+    if (Value <= XenbusStateInitWait || Value >= XenbusStateClosed) {

+      break;

+    }

+    DEBUG ((EFI_D_INFO,

+            "XenPvBlk: waiting backend state %d, current: %d\n",

+            XenbusStateInitWait, Value));

+    XenBusIo->WaitForWatch (XenBusIo, Dev->StateWatchToken);

+  }

+

+Close:

+  XenBusIo->UnregisterWatch (XenBusIo, Dev->StateWatchToken);

+  XenBusIo->XsRemove (XenBusIo, XST_NIL, "ring-ref");

+  XenBusIo->XsRemove (XenBusIo, XST_NIL, "event-channel");

+  XenBusIo->XsRemove (XenBusIo, XST_NIL, "protocol");

+

+  XenPvBlockFree (Dev);

+}

+

+STATIC

+VOID

+XenPvBlockWaitSlot (

+  IN XEN_BLOCK_FRONT_DEVICE *Dev

+  )

+{

+  /* Wait for a slot */

+  if (RING_FULL (&Dev->Ring)) {

+    while (TRUE) {

+      XenPvBlockAsyncIoPoll (Dev);

+      if (!RING_FULL (&Dev->Ring)) {

+        break;

+      }

+      /* Really no slot, could wait for an event on Dev->EventChannel. */

+    }

+  }

+}

+

+VOID

+XenPvBlockAsyncIo (

+  IN OUT XEN_BLOCK_FRONT_IO *IoData,

+  IN     BOOLEAN            IsWrite

+  )

+{

+  XEN_BLOCK_FRONT_DEVICE *Dev = IoData->Dev;

+  XENBUS_PROTOCOL *XenBusIo = Dev->XenBusIo;

+  blkif_request_t *Request;

+  RING_IDX RingIndex;

+  BOOLEAN Notify;

+  INT32 NumSegments, Index;

+  UINTN Start, End;

+

+  // Can't io at non-sector-aligned location

+  ASSERT(!(IoData->Sector & ((Dev->MediaInfo.SectorSize / 512) - 1)));

+  // Can't io non-sector-sized amounts

+  ASSERT(!(IoData->Size & (Dev->MediaInfo.SectorSize - 1)));

+  // Can't io non-sector-aligned buffer

+  ASSERT(!((UINTN) IoData->Buffer & (Dev->MediaInfo.SectorSize - 1)));

+

+  Start = (UINTN) IoData->Buffer & ~EFI_PAGE_MASK;

+  End = ((UINTN) IoData->Buffer + IoData->Size + EFI_PAGE_SIZE - 1) & ~EFI_PAGE_MASK;

+  IoData->NumRef = NumSegments = (End - Start) / EFI_PAGE_SIZE;

+

+  ASSERT (NumSegments <= BLKIF_MAX_SEGMENTS_PER_REQUEST);

+

+  XenPvBlockWaitSlot (Dev);

+  RingIndex = Dev->Ring.req_prod_pvt;

+  Request = RING_GET_REQUEST (&Dev->Ring, RingIndex);

+

+  Request->operation = IsWrite ? BLKIF_OP_WRITE : BLKIF_OP_READ;

+  Request->nr_segments = NumSegments;

+  Request->handle = Dev->DeviceId;

+  Request->id = (UINTN) IoData;

+  Request->sector_number = IoData->Sector;

+

+  for (Index = 0; Index < NumSegments; Index++) {

+    Request->seg[Index].first_sect = 0;

+    Request->seg[Index].last_sect = EFI_PAGE_SIZE / 512 - 1;

+  }

+  Request->seg[0].first_sect = ((UINTN) IoData->Buffer & EFI_PAGE_MASK) / 512;

+  Request->seg[NumSegments - 1].last_sect =

+      (((UINTN) IoData->Buffer + IoData->Size - 1) & EFI_PAGE_MASK) / 512;

+  for (Index = 0; Index < NumSegments; Index++) {

+    UINTN Data = Start + Index * EFI_PAGE_SIZE;

+    XenBusIo->GrantAccess (XenBusIo, Dev->DomainId,

+                           Data >> EFI_PAGE_SHIFT, IsWrite,

+                           &Request->seg[Index].gref);

+    IoData->GrantRef[Index] = Request->seg[Index].gref;

+  }

+

+  Dev->Ring.req_prod_pvt = RingIndex + 1;

+

+  MemoryFence ();

+  RING_PUSH_REQUESTS_AND_CHECK_NOTIFY (&Dev->Ring, Notify);

+

+  if (Notify) {

+    UINT32 ReturnCode;

+    ReturnCode = XenBusIo->EventChannelNotify (XenBusIo, Dev->EventChannel);

+    if (ReturnCode != 0) {

+      DEBUG ((EFI_D_ERROR,

+              "XenPvBlk: Unexpected return value from EventChannelNotify: %d\n",

+              ReturnCode));

+    }

+  }

+}

+

+EFI_STATUS

+XenPvBlockIo (

+  IN OUT XEN_BLOCK_FRONT_IO *IoData,

+  IN     BOOLEAN            IsWrite

+  )

+{

+  //

+  // Status value that correspond to an IO in progress.

+  //

+  IoData->Status = EFI_ALREADY_STARTED;

+  XenPvBlockAsyncIo (IoData, IsWrite);

+

+  while (IoData->Status == EFI_ALREADY_STARTED) {

+    XenPvBlockAsyncIoPoll (IoData->Dev);

+  }

+

+  return IoData->Status;

+}

+

+STATIC

+VOID

+XenPvBlockPushOperation (

+  IN XEN_BLOCK_FRONT_DEVICE *Dev,

+  IN UINT8                  Operation,

+  IN UINT64                 Id

+  )

+{

+  INT32 Index;

+  blkif_request_t *Request;

+  BOOLEAN Notify;

+

+  XenPvBlockWaitSlot (Dev);

+  Index = Dev->Ring.req_prod_pvt;

+  Request = RING_GET_REQUEST(&Dev->Ring, Index);

+  Request->operation = Operation;

+  Request->nr_segments = 0;

+  Request->handle = Dev->DeviceId;

+  Request->id = Id;

+  /* Not needed anyway, but the backend will check it */

+  Request->sector_number = 0;

+  Dev->Ring.req_prod_pvt = Index + 1;

+  MemoryFence ();

+  RING_PUSH_REQUESTS_AND_CHECK_NOTIFY (&Dev->Ring, Notify);

+  if (Notify) {

+    XENBUS_PROTOCOL *XenBusIo = Dev->XenBusIo;

+    UINT32 ReturnCode;

+    ReturnCode = XenBusIo->EventChannelNotify (XenBusIo, Dev->EventChannel);

+    if (ReturnCode != 0) {

+      DEBUG ((EFI_D_ERROR,

+              "XenPvBlk: Unexpected return value from EventChannelNotify: %d\n",

+              ReturnCode));

+    }

+  }

+}

+

+VOID

+XenPvBlockSync (

+  IN XEN_BLOCK_FRONT_DEVICE *Dev

+  )

+{

+  if (Dev->MediaInfo.ReadWrite) {

+    if (Dev->MediaInfo.FeatureBarrier) {

+      XenPvBlockPushOperation (Dev, BLKIF_OP_WRITE_BARRIER, 0);

+    }

+

+    if (Dev->MediaInfo.FeatureFlushCache) {

+      XenPvBlockPushOperation (Dev, BLKIF_OP_FLUSH_DISKCACHE, 0);

+    }

+  }

+

+  /* Note: This won't finish if another thread enqueues requests.  */

+  while (TRUE) {

+    XenPvBlockAsyncIoPoll (Dev);

+    if (RING_FREE_REQUESTS (&Dev->Ring) == RING_SIZE (&Dev->Ring)) {

+      break;

+    }

+  }

+}

+

+VOID

+XenPvBlockAsyncIoPoll (

+  IN XEN_BLOCK_FRONT_DEVICE *Dev

+  )

+{

+  RING_IDX ProducerIndex, ConsumerIndex;

+  blkif_response_t *Response;

+  INT32 More;

+

+  do {

+    ProducerIndex = Dev->Ring.sring->rsp_prod;

+    /* Ensure we see queued responses up to 'ProducerIndex'. */

+    MemoryFence ();

+    ConsumerIndex = Dev->Ring.rsp_cons;

+

+    while (ConsumerIndex != ProducerIndex) {

+      XEN_BLOCK_FRONT_IO *IoData = NULL;

+      INT16 Status;

+

+      Response = RING_GET_RESPONSE (&Dev->Ring, ConsumerIndex);

+

+      IoData = (VOID *) (UINTN) Response->id;

+      Status = Response->status;

+

+      switch (Response->operation) {

+      case BLKIF_OP_READ:

+      case BLKIF_OP_WRITE:

+        {

+          INT32 Index;

+

+          if (Status != BLKIF_RSP_OKAY) {

+            DEBUG ((EFI_D_ERROR,

+                    "XenPvBlk: "

+                    "%a error %d on %a at sector %p, num bytes %p\n",

+                    Response->operation == BLKIF_OP_READ ? "read" : "write",

+                    Status, IoData->Dev->NodeName,

+                    IoData->Sector,

+                    IoData->Size));

+          }

+

+          for (Index = 0; Index < IoData->NumRef; Index++) {

+            Dev->XenBusIo->GrantEndAccess (Dev->XenBusIo, IoData->GrantRef[Index]);

+          }

+

+          break;

+        }

+

+      case BLKIF_OP_WRITE_BARRIER:

+        if (Status != BLKIF_RSP_OKAY) {

+          DEBUG ((EFI_D_ERROR, "XenPvBlk: write barrier error %d\n", Status));

+        }

+        break;

+      case BLKIF_OP_FLUSH_DISKCACHE:

+        if (Status != BLKIF_RSP_OKAY) {

+          DEBUG ((EFI_D_ERROR, "XenPvBlk: flush error %d\n", Status));

+        }

+        break;

+

+      default:

+        DEBUG ((EFI_D_ERROR,

+                "XenPvBlk: unrecognized block operation %d response (status %d)\n",

+                Response->operation, Status));

+        break;

+      }

+

+      Dev->Ring.rsp_cons = ++ConsumerIndex;

+      if (IoData != NULL) {

+        IoData->Status = Status ? EFI_DEVICE_ERROR : EFI_SUCCESS;

+      }

+      if (Dev->Ring.rsp_cons != ConsumerIndex) {

+        /* We reentered, we must not continue here */

+        break;

+      }

+    }

+

+    RING_FINAL_CHECK_FOR_RESPONSES (&Dev->Ring, More);

+  } while (More != 0);

+}