Re: [PATCH v6 07/17] OvmfPkg: Introduce IoMmuAbsent Protocol GUID

[Laszlo Ersek <lersek@redhat.com>]

On 05/26/17 16:43, Brijesh Singh wrote:
> Platforms that optionally provide an IOMMU protocol should do so by
> including a DXE driver (usually called IoMmuDxe) that produces either
> the IOMMU protocol -- if the underlying capabilities are available --,
> or gIoMmuAbsentProtocolGuid, to signal that the IOMMU capability
> detection completed with negative result (i.e., no IOMMU will be
> available in the system).
> 
> In turn, DXE drivers (and library instances) that are supposed to use
> the IOMMU protocol if it is available should add the following to
> their DEPEX:
> 
> gEdkiiIoMmuProtocolGuid OR gIoMmuAbsentProtocolGuid
> 
> This ensures these client modules will only be dispatched after IOMMU
> detection completes (with positive or negative result).
> 
> 
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Leo Duran <leo.duran@amd.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Suggested-by: Jordan Justen <jordan.l.justen@intel.com>
> Suggested-by: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  OvmfPkg/OvmfPkg.dec | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
> index 5627be0bab0a..4241af10c3d0 100644
> --- a/OvmfPkg/OvmfPkg.dec
> +++ b/OvmfPkg/OvmfPkg.dec
> @@ -69,6 +69,7 @@ [Protocols]
>    gBlockMmioProtocolGuid              = {0x6b558ce3, 0x69e5, 0x4c67, {0xa6, 0x34, 0xf7, 0xfe, 0x72, 0xad, 0xbe, 0x84}}
>    gXenBusProtocolGuid                 = {0x3d3ca290, 0xb9a5, 0x11e3, {0xb7, 0x5d, 0xb8, 0xac, 0x6f, 0x7d, 0x65, 0xe6}}
>    gXenIoProtocolGuid                  = {0x6efac84f, 0x0ab0, 0x4747, {0x81, 0xbe, 0x85, 0x55, 0x62, 0x59, 0x04, 0x49}}
> +  gIoMmuAbsentProtocolGuid            = {0xf8775d50, 0x8abd, 0x4adf, {0x92, 0xac, 0x85, 0x3e, 0x51, 0xf6, 0xc8, 0xdc}}
>  
>  [PcdsFixedAtBuild]
>    gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvBase|0x0|UINT32|0
> 

Reviewed-by: Laszlo Ersek <lersek@redhat.com>