On Wed, Dec 4, 2024 at 6:57 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Wed, Dec 4, 2024, at 17:37, H. Peter Anvin wrote: > > On December 4, 2024 5:29:17 AM PST, Brian Gerst <brgerst@xxxxxxxxx> wrote: > >>> > >>> Removing this also drops the need for PHYS_ADDR_T_64BIT and SWIOTLB. > >>> PAE mode is still required to get access to the 'NX' bit on Atom > >>> 'Pentium M' and 'Core Duo' CPUs. > > > > By the way, there are 64-bit machines which require swiotlb. > > What I meant to write here was that CONFIG_X86_PAE no longer > needs to select PHYS_ADDR_T_64BIT and SWIOTLB. I ended up > splitting that change out to patch 06/11 with a better explanation, > so the sentence above is just wrong now and I've removed it > in my local copy now. > > Obviously 64-bit kernels still generally need swiotlb. Theoretically swiotlb can be useful on 32-bit machines as well for the DMA controllers that have < 32-bit mask. Dunno if swiotlb was designed to run on 32-bit machines at all. -- With Best Regards, Andy Shevchenko
