Re: [patch V5 00/38] x86/entry: Entry/exception code rework - the leftovers

Paul E. McKenney
2020-05-14T16:35:23Z

On Tue, May 12, 2020 at 11:00:59PM +0200, Thomas Gleixner wrote:
> Folks!
>
> This is V5 of the rework series. V4 can be found here:
>
> https://lore.kernel.org/r/20200505135341.730586321@linutronix.de
>
> Some of the non-x86 specific parts from part 1- 4 have been applied to the
> relevant tip branches and I merged them all together to base the rest on.
>
> I have applied most of the patches from part 1-4 on top after fixing up the
> small review comments all over the place. The result can be found here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git entry-base-v5
>
> I dropped:
>
> [patch V4 part 1 33/36] x86,tracing: Robustify ftrace_nmi_enter()
> [patch V4 part 2 10/18] x86/entry/64: Check IF in __preempt_enable_notrace()
> [patch V4 part 2 11/18] x86/entry/64: Mark ___preempt_schedule_notrace()
>
> from V4 because Peter's attempt to sanitize ftrace_nmi_enter/exit() and the
> underlying callchains turned out to be incomplete and cause the whole
> __preempt_schedule_notrace() hackery which is caused by a gazillion of
> preempt_disable_notrace() / preempt_enable_notrace() invocations in the
> full call chain. I found a better way to do that and that's in part 5 now.
>
> The remaining patches are mostly from part 5 of version 4 dealing with the
> #PF, device interrupts and the system vectors.
>
> The main differences to V4 part 5 are:
>
> - Provide nmi_enter/exit_notrace() which do not contain the
> ftrace_nmi_enter/exit() calls, use them in x86 and make the ftrace
> invocation explicit at a safe place.
>
> - A fix for the reworked SVM code
>
> - An optimization of asm_native_load_gs_index() which I found while
> staring at stuff in more detail
>
> - The removal of the x86 specific irq_regs implementation which was
> aside of two underscores in the variable name exactly the same thing
> as the generic variant.
>
> - Overhaul of the IRQ stack switching mechanics to avoid the objtool and
> unwinder nastiness of doing it in C inline ASM. As discussed here:
>
> https://lore.kernel.org/r/20200507161020.783541450@infradead.org
>
> We agreed on having the actual stack switch still in ASM and utilize it
> for device interrupts, soft interrupts and system vectors.
>
> This comes for the price of an indirect call, but the device interrupt
> handling has an indirect call and soft interrupts and most system
> vectors are indirect call laden already.
>
> There is a lightweight variant for the system vectors which do
> basically nothing, i.e. reschedule IPI and the KVM posted interrupt
> vectors. That variant runs on the interrupted stack and avoids the
> full entry/exit handling overhead by utilizing the conditional RCU
> variant of idtentry_enter/exit().
>
> - Addressing a few review comments.
>
> The series is also available from git:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git entry-v5-the-rest
>
> Running the new objtool checks results in two warning types:
>
> - The MCE code has an issue in the non-instrumentable section which is
> still under investigation and discussion
>
> - When paravirt is enabled then there are a few complaints about
> invoking indirect calls (PVOPS) which leave the noinstr sections
> but they are halfways straight forward to fix.
>
> Thanks,
>
> tglx

FWIW, the full set of one-hour rcutorture scenarios completed without
complaint on entry-v5-the-rest. Must be some mistake. ;-)

This is of course all within qemu/KVM guest OSes, so the next step
is to try it on bare metal.

Thanx, Paul

> 8<--------------
>
> arch/x86/include/asm/acrn.h | 11
> arch/x86/include/asm/entry_arch.h | 56 --
> arch/x86/include/asm/irq_regs.h | 32 -
> b/arch/x86/entry/calling.h | 25 -
> b/arch/x86/entry/common.c | 216 +++++++++-
> b/arch/x86/entry/entry_32.S | 260 +-----------
> b/arch/x86/entry/entry_64.S | 581 +++--------------------------
> b/arch/x86/entry/thunk_64.S | 9
> b/arch/x86/hyperv/hv_init.c | 9
> b/arch/x86/include/asm/apic.h | 33 -
> b/arch/x86/include/asm/hw_irq.h | 22 -
> b/arch/x86/include/asm/idtentry.h | 262 ++++++++++++-
> b/arch/x86/include/asm/irq.h | 6
> b/arch/x86/include/asm/irq_stack.h | 40 +
> b/arch/x86/include/asm/irq_work.h | 1
> b/arch/x86/include/asm/irqflags.h | 10
> b/arch/x86/include/asm/mshyperv.h | 13
> b/arch/x86/include/asm/trace/common.h | 4
> b/arch/x86/include/asm/trace/irq_vectors.h | 17
> b/arch/x86/include/asm/traps.h | 21 -
> b/arch/x86/include/asm/uv/uv_bau.h | 8
> b/arch/x86/kernel/apic/apic.c | 39 -
> b/arch/x86/kernel/apic/msi.c | 3
> b/arch/x86/kernel/apic/vector.c | 5
> b/arch/x86/kernel/cpu/acrn.c | 9
> b/arch/x86/kernel/cpu/mce/amd.c | 5
> b/arch/x86/kernel/cpu/mce/core.c | 4
> b/arch/x86/kernel/cpu/mce/therm_throt.c | 5
> b/arch/x86/kernel/cpu/mce/threshold.c | 5
> b/arch/x86/kernel/cpu/mshyperv.c | 22 -
> b/arch/x86/kernel/head_64.S | 7
> b/arch/x86/kernel/idt.c | 42 +-
> b/arch/x86/kernel/irq.c | 58 --
> b/arch/x86/kernel/irq_64.c | 17
> b/arch/x86/kernel/irq_work.c | 6
> b/arch/x86/kernel/kvm.c | 14
> b/arch/x86/kernel/nmi.c | 9
> b/arch/x86/kernel/smp.c | 37 -
> b/arch/x86/kernel/tracepoint.c | 17
> b/arch/x86/kernel/traps.c | 10
> b/arch/x86/kvm/svm/svm.c | 2
> b/arch/x86/mm/fault.c | 69 ++-
> b/arch/x86/platform/uv/tlb_uv.c | 2
> b/arch/x86/xen/enlighten_hvm.c | 12
> b/arch/x86/xen/enlighten_pv.c | 2
> b/arch/x86/xen/setup.c | 4
> b/arch/x86/xen/smp_pv.c | 3
> b/arch/x86/xen/xen-asm_32.S | 12
> b/arch/x86/xen/xen-asm_64.S | 4
> b/arch/x86/xen/xen-ops.h | 1
> b/drivers/xen/events/events_base.c | 6
> b/drivers/xen/preempt.c | 2
> b/include/linux/hardirq.h | 51 ++
> b/include/linux/rcutiny.h | 1
> b/include/linux/rcutree.h | 1
> b/include/xen/events.h | 7
> b/include/xen/xen-ops.h | 7
> b/kernel/rcu/tree.c | 5
> b/kernel/softirq.c | 35 +
> 59 files changed, 906 insertions(+), 1270 deletions(-)
>