On 02.02.24 09:07, Ryan Roberts wrote:
Split __flush_tlb_range() into __flush_tlb_range_nosync() +
__flush_tlb_range(), in the same way as the existing flush_tlb_page()
arrangement. This allows calling __flush_tlb_range_nosync() to elide the
trailing DSB. Forthcoming "contpte" code will take advantage of this
when clearing the young bit from a contiguous range of ptes.

Tested-by: John Hubbard <jhubb...@nvidia.com>
Signed-off-by: Ryan Roberts <ryan.robe...@arm.com>
---
  arch/arm64/include/asm/tlbflush.h | 13 +++++++++++--
  1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/tlbflush.h 
b/arch/arm64/include/asm/tlbflush.h
index 79e932a1bdf8..50a765917327 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -422,7 +422,7 @@ do {                                                        
                \
  #define __flush_s2_tlb_range_op(op, start, pages, stride, tlb_level) \
        __flush_tlb_range_op(op, start, pages, stride, 0, tlb_level, false, 
kvm_lpa2_is_enabled());
-static inline void __flush_tlb_range(struct vm_area_struct *vma,
+static inline void __flush_tlb_range_nosync(struct vm_area_struct *vma,
                                     unsigned long start, unsigned long end,
                                     unsigned long stride, bool last_level,
                                     int tlb_level)
@@ -456,10 +456,19 @@ static inline void __flush_tlb_range(struct 
vm_area_struct *vma,
                __flush_tlb_range_op(vae1is, start, pages, stride, asid,
                                     tlb_level, true, lpa2_is_enabled());
- dsb(ish);
        mmu_notifier_arch_invalidate_secondary_tlbs(vma->vm_mm, start, end);
  }
+static inline void __flush_tlb_range(struct vm_area_struct *vma,
+                                    unsigned long start, unsigned long end,
+                                    unsigned long stride, bool last_level,
+                                    int tlb_level)
+{
+       __flush_tlb_range_nosync(vma, start, end, stride,
+                                last_level, tlb_level);
+       dsb(ish);
+}
+
  static inline void flush_tlb_range(struct vm_area_struct *vma,
                                   unsigned long start, unsigned long end)
  {

You're now calling dsb() after mmu_notifier_arch_invalidate_secondary_tlbs().


In flush_tlb_mm(), we have the order

        dsb(ish);       
        mmu_notifier_arch_invalidate_secondary_tlbs()

In flush_tlb_page(), we have the effective order:

        mmu_notifier_arch_invalidate_secondary_tlbs()
        dsb(ish);

In flush_tlb_range(), we used to have the order:

        dsb(ish);
        mmu_notifier_arch_invalidate_secondary_tlbs();


So I *suspect* having that DSB before mmu_notifier_arch_invalidate_secondary_tlbs() is fine. Hopefully, nothing in there relies on that placement.

Maybe wort spelling out in the patch description

Reviewed-by: David Hildenbrand <da...@redhat.com>

--
Cheers,

David / dhildenb

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