Messages in this thread | | | Date | Fri, 26 Dec 2008 15:35:17 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 0/4] Remove interrupt stack table usage from x86_64 kernel (v2) |
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* Avi Kivity <avi@redhat.com> wrote:
> The interrupt stack table (IST) mechanism is the only thing preventing > kvm from deferring saving and reloading of some significant state. It > is also somewhat complicated. > > Remove it by switching the special exceptions to use the normal irqstack. > > Changes from v1: > - rebase on tip/master > - as a step, consolidate stack switching into a single macro > > Jeremy, Xen is also affected; please review. > > Avi Kivity (4): > x86: drop the use of the tss interrupt stack table (IST) > x86: Consolidate irq stack switching to a single macro > x86: Make interrupt stack switching atomic > x86: Move NMI back to interrupt stack > > arch/x86/include/asm/desc.h | 12 ----- > arch/x86/include/asm/page_64.h | 7 --- > arch/x86/include/asm/pda.h | 2 +- > arch/x86/include/asm/processor.h | 11 ---- > arch/x86/kernel/asm-offsets_64.c | 1 - > arch/x86/kernel/cpu/common.c | 35 -------------- > arch/x86/kernel/dumpstack_64.c | 96 -------------------------------------- > arch/x86/kernel/entry_64.S | 89 ++++++++++------------------------- > arch/x86/kernel/traps.c | 12 ++-- > 9 files changed, 33 insertions(+), 232 deletions(-)
applied to tip/x86/irq, thanks Avi!
They have the following commit IDs, and they are also in tip/master:
921e521: x86: move NMI back to interrupt stack 36ef6c9: x86: make interrupt stack switching atomic dd64891: x86: consolidate irq stack switching to a single macro 955a368: x86: drop the use of the tss interrupt stack table (IST)
I also started testing them in tip-qa.
I added the standard Impact-lines that we do in the x86 tree. Note that this patch:
dd64891: x86: consolidate irq stack switching to a single macro
isnt just consolidating IRQ entry assembly code, it is also changing the paranoidentry macros to do IRQ stack entries - and hence switches all but the NMI critical exception entries sequences over to the IRQ stack. Your later patch:
921e521: x86: move NMI back to interrupt stack
covers the NMI entry code too.
Please double-check that we indeed now have all the critical exceptions on the IRQ stack (they are all rare so testing alone wont show this), and please also double-check that we dont have more exceptions and entry callpaths on the IRQ stack than what we wanted. For example on a preemptible kernel (or in any codepath that calls schedule()) it is fatal to be on the IRQ stack, so this has to be very accurately coded.
Ingo
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