Re: [PATCH v2] Platform/RaspberryPi: Only enable IORT when 3G limit is disabled.

["Ard Biesheuvel" <ardb@kernel.org>]

On Wed, 17 Feb 2021 at 07:22, Andrei Warkentin <awarkentin@vmware.com> wrote:
>
> Reviewed-by: Andrei Warkentin <awarkentin@vmware.com>
> _

Pushed as 2cad1bd782b5..41b54dbb6803

Thanks all

_______________________________
> From: jlinton <lintonrjeremy@gmail.com>
> Sent: Wednesday, February 17, 2021 12:07 AM
> To: devel@edk2.groups.io <devel@edk2.groups.io>
> Cc: pete@akeo.ie <pete@akeo.ie>; Andrei Warkentin <awarkentin@vmware.com>; samer.el-haj-mahmoud@arm.com <samer.el-haj-mahmoud@arm.com>; leif@nuviainc.com <leif@nuviainc.com>; ardb+tianocore@kernel.org <ardb+tianocore@kernel.org>; Jeremy Linton <jeremy.linton@arm.com>
> Subject: [PATCH v2] Platform/RaspberryPi: Only enable IORT when 3G limit is disabled.
>
> From: Jeremy Linton <jeremy.linton@arm.com>
>
> The 3G limit, and the 2G IORT are intended to solve
> the same linux problem. They limit PCI DMA operations
> to the first 3G of RAM. Older linux kernels, as
> used with RHEL/Centos, trigger an assertion*
> when a DMA operation starts at a range that
> doesn't fit within the 2G range specified by the IORT.
>
> The simple solution is to only enable the IORT
> when the 3G flag is disabled and there is more
> than 3G installed.
>
> * https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fpftf%2FRPi4%2Fissues%2F123&amp;data=04%7C01%7Cawarkentin%40vmware.com%7C0c1dc1458ac14a84867b08d8d30a613a%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C1%7C637491388819273969%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=VlStuFf%2F5bvIAMarB%2F2djY64J7GDa1zEVMB61%2Fwjgn8%3D&amp;reserved=0
>
> Fixes: dac891da5cf3 ("Platform/RaspberryPi/AcpiTables: add a IORT ACPI table to limit XHCI DMA")
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
>  Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c b/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> index 19ef950f10..578f5ead8f 100644
> --- a/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> +++ b/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> @@ -755,6 +755,12 @@ HandleDynamicNamespace (
>      DEBUG ((DEBUG_ERROR, "Found namespace table not in table list.\n"));
>
>
>
>      return FALSE;
>
> +  case SIGNATURE_32 ('I', 'O', 'R', 'T'):
>
> +    // only enable the IORT on machines with >3G and no limit
>
> +    // to avoid problems with rhel/centos and other older OSs
>
> +    if (PcdGet32 (PcdRamLimitTo3GB) || !PcdGet32 (PcdRamMoreThan3GB)) {
>
> +      return FALSE;
>
> +    }
>
>    }
>
>
>
>    return TRUE;
>
> --
> 2.13.7
>