On Fri, 16 May 2014 12:45:15 -0700
Dave Hansen <d...@sr71.net> wrote:
>
> Steven had an alternative to this which has zero overhead when
> tracing is off where this includes the standard noops even when
> tracing is disabled. I'm unconvinced that the extra complexity
> of his apporach:
>
> http://lkml.kernel.org/r/20140508194508.561ed...@gandalf.local.home
>
> is worth it, expecially considering that the KVM code is already
> making page fault entry slower here. This solution is
> dirt-simple.
I just threw it out there as a suggestion. I don't care either way.
Acked-by: Steven Rostedt <rost...@goodmis.org>
You probably need an acked-by from hpa or one of the other x86
maintainers as it touches the generic traps.h header.
-- Steve
>
> Gleb, please apply.
>
> Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: x...@kernel.org
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Gleb Natapov <g...@redhat.com>
> Cc: "H. Peter Anvin" <h...@zytor.com>
> Cc: k...@vger.kernel.org
> Cc: Paolo Bonzini <pbonz...@redhat.com>
> Cc: Steven Rostedt <rost...@goodmis.org>
> ---
>
> b/arch/x86/include/asm/traps.h | 5 +++++
> b/arch/x86/kernel/kvm.c | 2 +-
> 2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff -puN arch/x86/include/asm/traps.h~muck-with-kvm-guest-code
> arch/x86/include/asm/traps.h
> --- a/arch/x86/include/asm/traps.h~muck-with-kvm-guest-code 2014-05-16
> 12:29:23.900429347 -0700
> +++ b/arch/x86/include/asm/traps.h 2014-05-16 12:29:23.905429570 -0700
> @@ -74,6 +74,11 @@ dotraplinkage void do_general_protection
> dotraplinkage void do_page_fault(struct pt_regs *, unsigned long);
> #ifdef CONFIG_TRACING
> dotraplinkage void trace_do_page_fault(struct pt_regs *, unsigned long);
> +#else
> +static inline void trace_do_page_fault(struct pt_regs *regs, unsigned long
> error)
> +{
> + do_page_fault(regs, error);
> +}
> #endif
> dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *, long);
> dotraplinkage void do_coprocessor_error(struct pt_regs *, long);
> diff -puN arch/x86/kernel/kvm.c~muck-with-kvm-guest-code arch/x86/kernel/kvm.c
> --- a/arch/x86/kernel/kvm.c~muck-with-kvm-guest-code 2014-05-16
> 12:29:23.902429437 -0700
> +++ b/arch/x86/kernel/kvm.c 2014-05-16 12:29:23.906429615 -0700
> @@ -259,7 +259,7 @@ do_async_page_fault(struct pt_regs *regs
>
> switch (kvm_read_and_reset_pf_reason()) {
> default:
> - do_page_fault(regs, error_code);
> + trace_do_page_fault(regs, error_code);
> break;
> case KVM_PV_REASON_PAGE_NOT_PRESENT:
> /* page is swapped out by the host. */
> _
--
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