[edk2-devel] [BUG/PATCH] Platform/RaspberryPi: Only enable IORT when 3G limit is disabled.
Jeremy Linton
jeremy.linton at arm.com
Mon Feb 8 18:59:28 UTC 2021
On 2/8/21 11:36 AM, Andrei Warkentin wrote:
> I'd rather we not set the PcdRamMoreThan3GB on a device with 1 or 2GB. I recognise you're using this to choose behavior for an old Linux version, but it's still non-sensical to the end user and it becomes a maintenance burden since the logic is no longer clear, so you might as well add a boot option to disable the IORT (and document as being for older Linux kernels) or just not install it if you explicitly being booted on a system with less RAM. I.e.
>
> if (PcdGet32 (PcdRamLimitTo3GB) || mModelInstalledMB < 2 * 1024) {
>
> return FALSE;
>
> }
Yah that works now too I guess. I split this off from the emmc2 patch
where I was lowering the IORT limit to 1G to force lower allocation.
But I ended up just providing an option to disable DMA, which is more
reliable anyway.
> ________________________________
> From: devel at edk2.groups.io <devel at edk2.groups.io> on behalf of Jeremy Linton via groups.io <jeremy.linton=arm.com at groups.io>
> Sent: Monday, February 1, 2021 4:44 PM
> To: devel at edk2.groups.io <devel at edk2.groups.io>
> Cc: pete at akeo.ie <pete at akeo.ie>; Andrei Warkentin <awarkentin at vmware.com>; samer.el-haj-mahmoud at arm.com <samer.el-haj-mahmoud at arm.com>; leif at nuviainc.com <leif at nuviainc.com>; ard.biesheuvel at arm.com <ard.biesheuvel at arm.com>; Jeremy Linton <jeremy.linton at arm.com>
> Subject: [edk2-devel] [BUG/PATCH] Platform/RaspberryPi: Only enable IORT when 3G limit is disabled.
>
> The 3G limit, and the 2G IORT are intended to solve
> the same linux problem, and 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 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.
>
> * https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fpftf%2FRPi4%2Fissues%2F123&data=04%7C01%7Cawarkentin%40vmware.com%7C92f310e07997434a267408d8c702f698%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C637478162838925480%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=dKbis45PDc6ciBMWvSime3ZhQJGOwYLN0OHTnhMSvvU%3D&reserved=0
>
> Fixes: dac891da5cf3 ("Platform/RaspberryPi/AcpiTables: add a IORT ACPI table to limit XHCI DMA")
> Signed-off-by: Jeremy Linton <jeremy.linton at arm.com>
> ---
> Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c | 26 +++++++++++++++++-----
> 1 file changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c b/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> index 19ef950f10..9581bc41e1 100644
> --- a/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> +++ b/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
> @@ -217,13 +217,23 @@ SetupVariables (
> ASSERT_EFI_ERROR (Status);
>
> }
>
>
>
> - if (mModelFamily >= 4 && mModelInstalledMB > 3 * 1024) {
>
> + if (mModelFamily >= 4) {
>
> + if (mModelInstalledMB > 3 * 1024) {
>
> + /*
>
> + * This allows changing PcdRamLimitTo3GB in forms.
>
> + */
>
> + Status = PcdSet32S (PcdRamMoreThan3GB, 1);
>
> + ASSERT_EFI_ERROR (Status);
>
> + } else {
>
> + Status = PcdSet32S (PcdRamMoreThan3GB, 0);
>
> + ASSERT_EFI_ERROR (Status);
>
> + }
>
> +
>
> /*
>
> - * This allows changing PcdRamLimitTo3GB in forms.
>
> + * Enable the "3G ram limit" on 2GB device because we
>
> + * are going to utlize that limit as a new/old kernel
>
> + * flag and also disable the IORT if the 3G limit is set.
>
> */
>
> - Status = PcdSet32S (PcdRamMoreThan3GB, 1);
>
> - ASSERT_EFI_ERROR (Status);
>
> -
>
> Size = sizeof (UINT32);
>
> Status = gRT->GetVariable (L"RamLimitTo3GB",
>
> &gConfigDxeFormSetGuid,
>
> @@ -755,6 +765,12 @@ 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
>
> + if (PcdGet32 (PcdRamLimitTo3GB)) {
>
> + return FALSE;
>
> + }
>
> }
>
>
>
> return TRUE;
>
> --
> 2.13.7
>
>
>
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