A Linux Fix Is On The Way For Some GPUs Having AMD Smart Access Memory Issue
Written by Michael Larabel in Radeon on 8 January 2021 at 12:20 AM EST. 7 Comments
RADEON --
A Linux fix is on the way for a new quirk to address an issue whereby some AMD Radeon graphics cards have an issue with the resizable BAR (AMD Smart Access Memory) handling that could lead to lower performance.

The quirk is about allowing BAR0 resizing to be done even for PCI Express graphics cards that don't advertise Resizable BAR support for a size large enough to span the entire video memory size but at least larger than the default.

Initially set as a quirk for this handling is the Sapphire Radeon RX 5600 XT Pulse (0x731f device ID) so now the CPU can fully access the BAR. Presumably with time we will see more graphics cards added to this quirk list to workaround problems with other AIB cards while ultimately this should also be addressable by updated video card BIOS too. It's likely other older GPUs are also affected given the AMD Smart Access Memory / Resizable BAR hasn't been a focus until now with the latest Radeon RX 6000 series hardware.

More details on this Linux quirk via this patch series that had been under review for several weeks while now appears ready for mainline. This goes along with other recent work around Linux optimizations for AMD S.A.M. and also restricting by default to Zen 3 and RDNA 2 due to bugs like this Navi 10 issue.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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