Messages in this thread | | | Date | Wed, 10 Apr 2024 09:50:20 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH v3 3/3] arm64: tlb: Allow range operation for MAX_TLBI_RANGE_PAGES |
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On Mon, 08 Apr 2024 09:43:44 +0100, Ryan Roberts <ryan.roberts@arm.com> wrote: > > On 05/04/2024 04:58, Gavin Shan wrote: > > MAX_TLBI_RANGE_PAGES pages is covered by SCALE#3 and NUM#31 and it's > > supported now. Allow TLBI RANGE operation when the number of pages is > > equal to MAX_TLBI_RANGE_PAGES in __flush_tlb_range_nosync(). > > > > Suggested-by: Marc Zyngier <maz@kernel.org> > > Signed-off-by: Gavin Shan <gshan@redhat.com> > > Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> > > > --- > > arch/arm64/include/asm/tlbflush.h | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h > > index 243d71f7bc1f..95fbc8c05607 100644 > > --- a/arch/arm64/include/asm/tlbflush.h > > +++ b/arch/arm64/include/asm/tlbflush.h > > @@ -446,11 +446,11 @@ static inline void __flush_tlb_range_nosync(struct vm_area_struct *vma, > > * When not uses TLB range ops, we can handle up to > > * (MAX_DVM_OPS - 1) pages; > > * When uses TLB range ops, we can handle up to > > - * (MAX_TLBI_RANGE_PAGES - 1) pages. > > + * MAX_TLBI_RANGE_PAGES pages. > > */ > > if ((!system_supports_tlb_range() && > > (end - start) >= (MAX_DVM_OPS * stride)) || > > - pages >= MAX_TLBI_RANGE_PAGES) { > > + pages > MAX_TLBI_RANGE_PAGES) { > > As a further enhancement, I wonder if it might be better to test: > > pages * 4 / MAX_TLBI_RANGE_PAGES > MAX_DVM_OPS > > Then add an extra loop over __flush_tlb_range_op(), like KVM does. > > The math is trying to express that there are a maximum of 4 tlbi range > instructions for MAX_TLBI_RANGE_PAGES pages (1 per scale) and we only need to > fall back to flushing the whole mm if it could generate more than MAX_DVM_OPS ops.
That'd be a good enhancement indeed, although I wonder if that occurs as often as we see it on the KVM side. But in any case, adding consistency amongst the users of __flush_tlb_range_op() can only be beneficial.
Thanks,
M.
-- Without deviation from the norm, progress is not possible.
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