[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2] x86/traps: Re-enable interrupts after reading cr2 in the #PF handler
On Wed, Sep 18, 2024 at 02:05:54PM +0100, Alejandro Vallejo wrote: > Moves sti directly after the cr2 read and immediately after the #PF > handler. I think you need to add some context about why this is needed, iow: avoid corrupting %cr2 if a nested 3PF happens. > While in the area, remove redundant q suffix to a movq in entry.S > > Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx> Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx> One nit below. > --- > Got lost alongside other patches. Here's the promised v2. > > pipeline: > https://gitlab.com/xen-project/people/agvallejo/xen/-/pipelines/1458699639 > v1: > https://lore.kernel.org/xen-devel/20240911145823.12066-1-alejandro.vallejo@xxxxxxxxx/ > > v2: > * (cosmetic), add whitespace after comma > * Added ASSERT(local_irq_is_enabled()) to do_page_fault() > * Only re-enable interrupts if they were enabled in the interrupted > context. > --- > xen/arch/x86/traps.c | 8 ++++++++ > xen/arch/x86/x86_64/entry.S | 20 ++++++++++++++++---- > 2 files changed, 24 insertions(+), 4 deletions(-) > > diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c > index 708136f62558..a9c2c607eb08 100644 > --- a/xen/arch/x86/traps.c > +++ b/xen/arch/x86/traps.c > @@ -1600,6 +1600,14 @@ void asmlinkage do_page_fault(struct cpu_user_regs > *regs) > > addr = read_cr2(); > > + /* > + * Don't re-enable interrupts if we were running an IRQ-off region when > + * we hit the page fault, or we'll break that code. > + */ > + ASSERT(!local_irq_is_enabled()); > + if ( regs->flags & X86_EFLAGS_IF ) > + local_irq_enable(); > + > /* fixup_page_fault() might change regs->error_code, so cache it here. */ > error_code = regs->error_code; > > diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S > index b8482de8ee5b..218e5ea85efb 100644 > --- a/xen/arch/x86/x86_64/entry.S > +++ b/xen/arch/x86/x86_64/entry.S > @@ -844,9 +844,9 @@ handle_exception_saved: > #elif !defined(CONFIG_PV) > ASSERT_CONTEXT_IS_XEN > #endif /* CONFIG_PV */ > - sti > -1: movq %rsp,%rdi > - movzbl UREGS_entry_vector(%rsp),%eax > +.Ldispatch_handlers: Maybe 'dispatch_exception', since it's only exceptions that are handled here? dispatch_handlers seems a bit too generic, but no strong opinion. Thanks, Roger.
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