On Tue, Aug 23, 2022 at 11:25 AM Dongli Zhang dongli.zhang@oracle.com wrote:
Adding Robin, Yu and swiotlb list.
Thanks.
There is an on-going discussion whether to revert this patch, because it breaks a corner case in MIPS
I wouldn't call it a corner case. Cavium Octeon is the major platform we use to test Debian MIPS ports [1], and 4 out of 5 best-selling Wi-Fi routers are MIPS-based [2].
[1] https://wiki.debian.org/MIPSPort [2] https://www.amazon.com/bestsellers/pc/300189
when many kernel CONFIGs are not enabled (related to PCI and device). As a result, MIPS pre-allocates only PAGE_SIZE buffer as swiotlb.
https://lore.kernel.org/all/20220820012031.1285979-1-yuzhao@google.com/
However, the core idea of the patch is to panic on purpose if the swiotlb is configured with <1MB memory, in order to sync with the remap failure handler in swiotlb_init_remap().
Therefore, I am waiting for suggestion from Christoph whether (1) to revert this patch, or (2) enforce the restriction to disallow <1MB allocation.
There are other archs (arm, ppc, riscv, s390, etc.) that call swiotlb_init(). Have you verified them all?