Nicholas Piggin [nicholas.piggin@xxxxxxxxx] wrote: > On Mon, 17 Jul 2017 16:43:19 -0700 > Haren Myneni <haren@xxxxxxxxxxxxxxxxxx> wrote: > > > [PATCH V2 0/6] Enable NX 842 compression engine on Power9 > > This patchset depends on VAS kernel changes: > > https://lists.ozlabs.org/pipermail/linuxppc-dev/2017-May/158178.html > > Just a question, we no longer invalidate the copy buffer on context > switch after this patch: > > 07d2a628bc ("powerpc/64s: Avoid cpabort in context switch when possible") > > If your vas address mappings are visible only to kernel, only used in > process / kthread context, and only used with kernel preemption disabled, > this is okay. Kernel preemption is not explicitly disabled in the NX driver I think and > > If userspace can possibly copy/paste to the mappings or if you need to > sleep or call this from interrupt context, we need to work out how to > invalidate the copy buffer. user space cannot copy/paste to the mappings yet (that mechanism is further out). NX driver calls: vas_copy(&crb, ...); vas_paste(addr, ...); but not from an interrupt context. Can/should we disable premption between the copy/paste and to avoid having to invalidate the copy buffer? Sukadev
