On Thu, Jun 29, 2017 at 10:41:44PM -0700, Andy Lutomirski wrote: > On Thu, Jun 29, 2017 at 10:05 PM, Andy Lutomirski <l...@kernel.org> wrote: > > Hmm. There's another option that might be considerably nicer, though: > > put the IRQ stack at a known (at link time) position *in percpu > > space*. (Presumably it already is -- I haven't checked.) Then we do: > > > > .macro ENTER_IRQ_STACK old_rsp > > DEBUG_ENTRY_ASSERT_IRQS_OFF > > movq %rsp, \old_rsp > > incl PER_CPU_VAR(irq_count) > > > > /* > > * Right now, if we just incremented irq_count to zero, we've > > * claimed the IRQ stack but we haven't switched to it yet. > > * Anything that can interrupt us here without using IST > > * must be *extremely* careful to limit its stack usage. > > */ > > jnz .Lpush_old_rsp_\@ > > movq \old_rsp, PER_CPU_VAR(top_word_in_irq_stack) > > movq PER_CPU_VAR(irq_stack_ptr), %rsp > > .Lpush_old_rsp_\@: > > pushq \old_rsp > > .endm > > > > How about the two commits here (well, soon to be there once gitweb catches > up): > > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_irq_stack&id=0f56a55bb133cd53ccb78ca51378086296618322 > > If you like them, want to add them to your series?
The second patch looks good to me, thanks. I can pick up the patches. A few comments about the first patch: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_irq_stack&id=3e2aa2102cc1c5e60d4a8637bff78d0478a55059 - It uses a '693:' label instead of '.Lirqs_off_\@:' - There's a comment I don't follow: "Anything that can interrupt us here without using IST must be *extremely* careful to limit its stack usage." What specifically could interrupt there without using IST? - Since do_softirq_own_stack() is a callable function, I think it still needs to save rbp. - Why change the "jmp error_exit" to "ret" in xen_do_hypervisor_callback()? -- Josh
