Re: [edk2-devel] [PATCH v3 1/2] MdeModulePkg/AhciPei: Limit max transfer blocknum for 48-bit address

["Ni, Ray" <ray.ni@intel.com>]

Reviewed-by: Ray Ni <ray.ni@intel.com>

> -----Original Message-----
> From: devel@edk2.groups.io [mailto:devel@edk2.groups.io] On Behalf Of
> Wu, Hao A
> Sent: Tuesday, April 23, 2019 1:06 AM
> To: devel@edk2.groups.io
> Cc: Wu, Hao A <hao.a.wu@intel.com>; Ni, Ray <ray.ni@intel.com>; Dong,
> Eric <eric.dong@intel.com>; Wang, Jian J <jian.j.wang@intel.com>
> Subject: [edk2-devel] [PATCH v3 1/2] MdeModulePkg/AhciPei: Limit max
> transfer blocknum for 48-bit address
> 
> 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.
> 
> According to PCDs:
> gIntelSiliconPkgTokenSpaceGuid.PcdVTdPeiDmaBufferSize|0x00400000
> gIntelSiliconPkgTokenSpaceGuid.PcdVTdPeiDmaBufferSizeS3|0x00200000
> 
> The default buffer size allocated for IOMMU mapping is:
> * 4M bytes for non-S3 cases;
> * 2M bytes for S3
> 
> For ATA devices in 48-bit address mode, the maximum block number is
> currently set to 0xFFFF. For a device with block size equal to 512 bytes, the
> maximum buffer allowed for mapping within AhciPei driver will be close to
> 32M bytes. Thus, this commit will limit the 48-bit mode maximum block
> number to 0x800, which means 1M-byte maximum buffer for mapping when
> the block size of a device is 512 bytes. By doing so, potential failure on calls
> to the IOMMU 'Map' service can be avoided.
> 
> 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 | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c
> b/MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c
> index a83c213a47..11754b3057 100644
> --- a/MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c
> +++ b/MdeModulePkg/Bus/Ata/AhciPei/AhciMode.c
> @@ -48,7 +48,13 @@ 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 for VTd PEI DMA buffer on platforms, the
> +driver // limits the maximum transfer block number for 48-bit addressing.
> +// Here, setting to 0x800 means that for device with 512-byte block
> +size, the // maximum buffer for DMA mapping will be 1M bytes in size.
> +//
> +#define MAX_48BIT_TRANSFER_BLOCK_NUM     0x800
> 
>  UINT32 mMaxTransferBlockNumber[2] = {
>    MAX_28BIT_TRANSFER_BLOCK_NUM,
> --
> 2.12.0.windows.1
> 
> 
>