[PATCH v2 1/2] MdeModulePkg/AhciPei: Limit max transfer blocknum for 48-bit address

["Wu, Hao A" <hao.a.wu@intel.com>]

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1483

Due to the limited resource on the VTd DMA buffer size in the PEI phase,
the driver will limit the maximum transfer block number for 48-bit
addressing.

This commit aims to prevent the potential failure on calls to the IOMMU
'Map' service.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
---
 MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c b/MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c
index a83c213a47..f9174e68b1 100644
--- a/MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c
+++ b/MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c
@@ -48,7 +48,12 @@ UINT8  mAtaTrustCommands[2] = {
 // Look up table (Lba48Bit) for maximum transfer block number
 //
 #define MAX_28BIT_TRANSFER_BLOCK_NUM     0x100
-#define MAX_48BIT_TRANSFER_BLOCK_NUM     0xFFFF
+//
+// Due to limited resource on VTd PEI DMA buffer size, driver limits the
+// maximum transfer block number for 48-bit addressing.
+// Setting to 0x800 here means 1M bytes for device with 512-byte block size.
+//
+#define MAX_48BIT_TRANSFER_BLOCK_NUM     0x800
 
 UINT32 mMaxTransferBlockNumber[2] = {
   MAX_28BIT_TRANSFER_BLOCK_NUM,
-- 
2.12.0.windows.1