[PATCH v2 12/23] OvmfPkg/VirtioLib: add functions to map/unmap VRING

[Brijesh Singh <brijesh.singh@amd.com>]

Add functions to map and unmap the ring buffer with BusMasterCommonBuffer
so that ring can be accessed by both guest and hypervisor.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/Include/Library/VirtioLib.h   | 25 +++++++++++
 OvmfPkg/Library/VirtioLib/VirtioLib.c | 44 ++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/OvmfPkg/Include/Library/VirtioLib.h b/OvmfPkg/Include/Library/VirtioLib.h
index ca0b217a04eb..1efb02a68cf1 100644
--- a/OvmfPkg/Include/Library/VirtioLib.h
+++ b/OvmfPkg/Include/Library/VirtioLib.h
@@ -62,6 +62,31 @@ VirtioRingInit (
 
 /**
 
+  Map the ring buffer so that it can be accessed equally by both guest
+  and hypervisor.
+
+  @param[in]      VirtIo          The virtio device instance.
+
+  @param[in]      Ring            The virtio ring to map.
+
+  @param[out]     RingBaseShift   
+
+  @param[out]     Mapping         A resulting token to pass to
+                                  VirtIo->UnmapSharedBuffer().
+
+  @return         Status from VirtIo->MapSharedBuffer()
+**/
+EFI_STATUS
+EFIAPI
+VirtioRingMap (
+  IN  VIRTIO_DEVICE_PROTOCOL *VirtIo,
+  IN  VRING                  *Ring,
+  OUT UINT64                 *RingBaseShift,
+  OUT VOID                   **Mapping
+  );
+
+/**
+
   Tear down the internal resources of a configured virtio ring.
 
   The caller is responsible to stop the host from using this ring before
diff --git a/OvmfPkg/Library/VirtioLib/VirtioLib.c b/OvmfPkg/Library/VirtioLib/VirtioLib.c
index 5b64d18a8d6f..7d07dcc09d3d 100644
--- a/OvmfPkg/Library/VirtioLib/VirtioLib.c
+++ b/OvmfPkg/Library/VirtioLib/VirtioLib.c
@@ -498,3 +498,47 @@ Failed:
   *Mapping = NULL;
   return EFI_OUT_OF_RESOURCES;
 }
+
+/**
+
+  Map the ring buffer so that it can be accessed equally by both guest
+  and hypervisor.
+
+  @param[in]      VirtIo          The virtio device instance.
+
+  @param[in]      Ring            The virtio ring to map.
+
+  @param[out]     RingBaseShift   RingBaseShift
+
+  @param[out]     Mapping         A resulting token to pass to
+                                  VirtIo->UnmapSharedBuffer().
+
+  @return         Status code from VirtIo->MapSharedBuffer()
+**/
+EFI_STATUS
+EFIAPI
+VirtioRingMap (
+  IN  VIRTIO_DEVICE_PROTOCOL *VirtIo,
+  IN  VRING                  *Ring,
+  OUT UINT64                 *RingBaseShift,
+  OUT VOID                   **Mapping
+  )
+{
+  EFI_STATUS        Status;
+  PHYSICAL_ADDRESS  DeviceAddress;
+
+  Status = VirtioMapAllBytesInSharedBuffer (
+             VirtIo,
+             VirtioOperationBusMasterCommonBuffer,
+             Ring->Base,
+             EFI_PAGES_TO_SIZE (Ring->NumPages),
+             &DeviceAddress,
+             Mapping
+             );
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  *RingBaseShift = DeviceAddress - (UINT64)(UINTN)Ring->Base;
+  return EFI_SUCCESS;
+}
-- 
2.7.4