Re: [RESEND PATCH v5 05/11] arm64: tlb: Refactor the core flush algorithm of __flush_tlb_range

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On Tue, Jul 4, 2023 at 5:11 PM Gavin Shan <gshan@xxxxxxxxxx> wrote:
>
> On 6/22/23 03:49, Raghavendra Rao Ananta wrote:
> > Currently, the core TLB flush functionality of __flush_tlb_range()
> > hardcodes vae1is (and variants) for the flush operation. In the
> > upcoming patches, the KVM code reuses this core algorithm with
> > ipas2e1is for range based TLB invalidations based on the IPA.
> > Hence, extract the core flush functionality of __flush_tlb_range()
> > into its own macro that accepts an 'op' argument to pass any
> > TLBI operation, such that other callers (KVM) can benefit.
> >
> > No functional changes intended.
> >
> > Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> > Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> > ---
> >   arch/arm64/include/asm/tlbflush.h | 108 +++++++++++++++---------------
> >   1 file changed, 55 insertions(+), 53 deletions(-)
> >
>
> With the following nits addressed:
>
> Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>
>
> > diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> > index 412a3b9a3c25d..4775378b6da1b 100644
> > --- a/arch/arm64/include/asm/tlbflush.h
> > +++ b/arch/arm64/include/asm/tlbflush.h
> > @@ -278,14 +278,61 @@ static inline void flush_tlb_page(struct vm_area_struct *vma,
> >    */
> >   #define MAX_TLBI_OPS        PTRS_PER_PTE
> >
> > +/* When the CPU does not support TLB range operations, flush the TLB
> > + * entries one by one at the granularity of 'stride'. If the TLB
> > + * range ops are supported, then:
> > + *
> > + * 1. If 'pages' is odd, flush the first page through non-range
> > + *    operations;
> > + *
> > + * 2. For remaining pages: the minimum range granularity is decided
> > + *    by 'scale', so multiple range TLBI operations may be required.
> > + *    Start from scale = 0, flush the corresponding number of pages
> > + *    ((num+1)*2^(5*scale+1) starting from 'addr'), then increase it
> > + *    until no pages left.
> > + *
> > + * Note that certain ranges can be represented by either num = 31 and
> > + * scale or num = 0 and scale + 1. The loop below favours the latter
> > + * since num is limited to 30 by the __TLBI_RANGE_NUM() macro.
> > + */
> > +#define __flush_tlb_range_op(op, start, pages, stride,                       \
> > +                             asid, tlb_level, tlbi_user) do {        \
> > +     int num = 0;                                                    \
> > +     int scale = 0;                                                  \
> > +     unsigned long addr;                                             \
> > +                                                                     \
> > +     while (pages > 0) {                                             \
> > +             if (!system_supports_tlb_range() ||                     \
> > +                 pages % 2 == 1) {                                   \
> > +                     addr = __TLBI_VADDR(start, asid);               \
> > +                     __tlbi_level(op, addr, tlb_level);              \
> > +                     if (tlbi_user)                                  \
> > +                             __tlbi_user_level(op, addr, tlb_level); \
> > +                     start += stride;                                \
> > +                     pages -= stride >> PAGE_SHIFT;                  \
> > +                     continue;                                       \
> > +             }                                                       \
> > +                                                                     \
> > +             num = __TLBI_RANGE_NUM(pages, scale);                   \
> > +             if (num >= 0) {                                         \
> > +                     addr = __TLBI_VADDR_RANGE(start, asid, scale,   \
> > +                                               num, tlb_level);      \
> > +                     __tlbi(r##op, addr);                            \
> > +                     if (tlbi_user)                                  \
> > +                             __tlbi_user(r##op, addr);               \
> > +                     start += __TLBI_RANGE_PAGES(num, scale) << PAGE_SHIFT; \
> > +                     pages -= __TLBI_RANGE_PAGES(num, scale);        \
> > +             }                                                       \
> > +             scale++;                                                \
> > +     }                                                               \
> > +} while (0)
> > +
>
> There is a warning reported from 'checkpatch.pl'.
>
>      WARNING: suspect code indent for conditional statements (32, 8)
>      #52: FILE: arch/arm64/include/asm/tlbflush.h:299:
>      +                          asid, tlb_level, tlbi_user) do {        \
>      [...]
>      +  unsigned long addr;                                             \
>
>      total: 0 errors, 1 warnings, 125 lines checked
>
> You probably need to tweak it as below, to avoid the warning.
>
>      #define __flush_tlb_range_op(op, start, pages, stride,                \
>                                   asid, tlb_level, tlbi_user)              \
>      do {                                                                  \
>
Thanks for the suggestion, Gavin. I'll fix this.

- Raghavendra
>
> >   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)
> >   {
> > -     int num = 0;
> > -     int scale = 0;
> > -     unsigned long asid, addr, pages;
> > +     unsigned long asid, pages;
> >
> >       start = round_down(start, stride);
> >       end = round_up(end, stride);
> > @@ -307,56 +354,11 @@ static inline void __flush_tlb_range(struct vm_area_struct *vma,
> >       dsb(ishst);
> >       asid = ASID(vma->vm_mm);
> >
> > -     /*
> > -      * When the CPU does not support TLB range operations, flush the TLB
> > -      * entries one by one at the granularity of 'stride'. If the TLB
> > -      * range ops are supported, then:
> > -      *
> > -      * 1. If 'pages' is odd, flush the first page through non-range
> > -      *    operations;
> > -      *
> > -      * 2. For remaining pages: the minimum range granularity is decided
> > -      *    by 'scale', so multiple range TLBI operations may be required.
> > -      *    Start from scale = 0, flush the corresponding number of pages
> > -      *    ((num+1)*2^(5*scale+1) starting from 'addr'), then increase it
> > -      *    until no pages left.
> > -      *
> > -      * Note that certain ranges can be represented by either num = 31 and
> > -      * scale or num = 0 and scale + 1. The loop below favours the latter
> > -      * since num is limited to 30 by the __TLBI_RANGE_NUM() macro.
> > -      */
> > -     while (pages > 0) {
> > -             if (!system_supports_tlb_range() ||
> > -                 pages % 2 == 1) {
> > -                     addr = __TLBI_VADDR(start, asid);
> > -                     if (last_level) {
> > -                             __tlbi_level(vale1is, addr, tlb_level);
> > -                             __tlbi_user_level(vale1is, addr, tlb_level);
> > -                     } else {
> > -                             __tlbi_level(vae1is, addr, tlb_level);
> > -                             __tlbi_user_level(vae1is, addr, tlb_level);
> > -                     }
> > -                     start += stride;
> > -                     pages -= stride >> PAGE_SHIFT;
> > -                     continue;
> > -             }
> > -
> > -             num = __TLBI_RANGE_NUM(pages, scale);
> > -             if (num >= 0) {
> > -                     addr = __TLBI_VADDR_RANGE(start, asid, scale,
> > -                                               num, tlb_level);
> > -                     if (last_level) {
> > -                             __tlbi(rvale1is, addr);
> > -                             __tlbi_user(rvale1is, addr);
> > -                     } else {
> > -                             __tlbi(rvae1is, addr);
> > -                             __tlbi_user(rvae1is, addr);
> > -                     }
> > -                     start += __TLBI_RANGE_PAGES(num, scale) << PAGE_SHIFT;
> > -                     pages -= __TLBI_RANGE_PAGES(num, scale);
> > -             }
> > -             scale++;
> > -     }
> > +     if (last_level)
> > +             __flush_tlb_range_op(vale1is, start, pages, stride, asid, tlb_level, true);
> > +     else
> > +             __flush_tlb_range_op(vae1is, start, pages, stride, asid, tlb_level, true);
> > +
> >       dsb(ish);
> >   }
> >
>
> Thanks,
> Gavin
>




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