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

["Paul E. McKenney" <paulmck@kernel.org>]

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(-)
>