Re: [PATCH v2 11/13] arm64: mm: More flags for __flush_tlb_range()

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Tue, 27 Jan 2026 13:50:06 +0000
Ryan Roberts <ryan.roberts@arm.com> wrote:

> On 27/01/2026 12:45, Jonathan Cameron wrote:
> > On Mon, 19 Jan 2026 17:21:58 +0000
> > Ryan Roberts <ryan.roberts@arm.com> wrote:
> >   
> >> Refactor function variants with "_nosync", "_local" and "_nonotify" into
> >> a single __always_inline implementation that takes flags and rely on
> >> constant folding to select the parts that are actually needed at any
> >> given callsite, based on the provided flags.
> >>
> >> Flags all live in the tlbf_t (TLB flags) type; TLBF_NONE (0) continues
> >> to provide the strongest semantics (i.e. evict from walk cache,
> >> broadcast, synchronise and notify). Each flag reduces the strength in
> >> some way; TLBF_NONOTIFY, TLBF_NOSYNC and TLBF_NOBROADCAST are added to
> >> complement the existing TLBF_NOWALKCACHE.  
> > 
> > Unless I'm missing something the case of TLBF_NOBROADCAST but not
> > TLBF_NOWALKCACHE isn't currently used.  
> 
> Currect but the next couple of patches start using TLBF_NOBROADCAST without
> TLBF_NOWALKCACHE. TLBF_NOWALKCACHE is used without TLBF_NOBROADCAST in this patch.
> 
> >   
> > I wonder if bringing that in with a user will make it easier to see what
> > is going on.  
> 
> I'm not sure I understand the suggestion. This patch is using both flags so I
> can't really defer introducing one of them. It's just that (for this patch only)
> it never uses TLBF_NOBROADCAST without TLBF_NOWALKCACHE.

Would be a case of lobbing in a build_bug_on() or similar, but this was
mainly that I hadn't read the later patches at this point (or at least
not such that they were still in my memory).

Perhaps a breadcrumb just to say that new combination is added, but
not used until later patches.
> 
> > 
> > Otherwise, 3 vs 2 underscores? Can we come up with something easier
> > to read than that?  
> 
> You mean for ___flush_tlb_range() below? Yeah fair enough. How about
> __do_flush_tlb_range() as the common function?

That works for me.

J
> 
> Thanks,
> Ryan
> 
> 
> 
> >   
> >>
> >> The result is a clearer, simpler, more powerful API.
> >>
> >> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> >> ---
> >>  arch/arm64/include/asm/tlbflush.h | 107 +++++++++++++++++++-----------
> >>  arch/arm64/mm/contpte.c           |   9 ++-
> >>  2 files changed, 74 insertions(+), 42 deletions(-)
> >>
> >> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> >> index 1ad1c864e1f8..f03831cd8719 100644
> >> --- a/arch/arm64/include/asm/tlbflush.h
> >> +++ b/arch/arm64/include/asm/tlbflush.h
> >> @@ -107,6 +107,12 @@ static inline unsigned long get_trans_granule(void)
> >>  
> >>  typedef void (*tlbi_op)(u64 arg);
> >>  
> >> +static __always_inline void vae1(u64 arg)
> >> +{
> >> +	__tlbi(vae1, arg);
> >> +	__tlbi_user(vae1, arg);
> >> +}
> >> +
> >>  static __always_inline void vae1is(u64 arg)
> >>  {
> >>  	__tlbi(vae1is, arg);
> >> @@ -275,7 +281,10 @@ static inline void __tlbi_level(tlbi_op op, u64 addr, u32 level)
> >>   *		no invalidation may take place. In the case where the level
> >>   *		cannot be easily determined, the value TLBI_TTL_UNKNOWN will
> >>   *		perform a non-hinted invalidation. flags may be TLBF_NONE (0) or
> >> - *		TLBF_NOWALKCACHE (elide eviction of walk cache entries).
> >> + *		any combination of TLBF_NOWALKCACHE (elide eviction of walk
> >> + *		cache entries), TLBF_NONOTIFY (don't call mmu notifiers),
> >> + *		TLBF_NOSYNC (don't issue trailing dsb) and TLBF_NOBROADCAST
> >> + *		(only perform the invalidation for the local cpu).
> >>   *
> >>   *	local_flush_tlb_page(vma, addr)
> >>   *		Local variant of flush_tlb_page().  Stale TLB entries may
> >> @@ -285,12 +294,6 @@ static inline void __tlbi_level(tlbi_op op, u64 addr, u32 level)
> >>   *		Same as local_flush_tlb_page() except MMU notifier will not be
> >>   *		called.
> >>   *
> >> - *	local_flush_tlb_contpte(vma, addr)
> >> - *		Invalidate the virtual-address range
> >> - *		'[addr, addr+CONT_PTE_SIZE)' mapped with contpte on local CPU
> >> - *		for the user address space corresponding to 'vma->mm'.  Stale
> >> - *		TLB entries may remain in remote CPUs.
> >> - *
> >>   *	Finally, take a look at asm/tlb.h to see how tlb_flush() is implemented
> >>   *	on top of these routines, since that is our interface to the mmu_gather
> >>   *	API as used by munmap() and friends.
> >> @@ -435,6 +438,12 @@ static inline void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
> >>   *    operations can only span an even number of pages. We save this for last to
> >>   *    ensure 64KB start alignment is maintained for the LPA2 case.
> >>   */
> >> +static __always_inline void rvae1(u64 arg)
> >> +{
> >> +	__tlbi(rvae1, arg);
> >> +	__tlbi_user(rvae1, arg);
> >> +}
> >> +
> >>  static __always_inline void rvae1is(u64 arg)
> >>  {
> >>  	__tlbi(rvae1is, arg);
> >> @@ -541,15 +550,23 @@ typedef unsigned __bitwise tlbf_t;
> >>  /* Invalidate tlb entries only, leaving the page table walk cache intact. */
> >>  #define TLBF_NOWALKCACHE	((__force tlbf_t)BIT(0))
> >>  
> >> -static inline void __flush_tlb_range_nosync(struct mm_struct *mm,
> >> -				     unsigned long start, unsigned long end,
> >> -				     unsigned long stride, int tlb_level,
> >> -				     tlbf_t flags)
> >> +/* Skip the trailing dsb after issuing tlbi. */
> >> +#define TLBF_NOSYNC		((__force tlbf_t)BIT(1))
> >> +
> >> +/* Suppress tlb notifier callbacks for this flush operation. */
> >> +#define TLBF_NONOTIFY		((__force tlbf_t)BIT(2))
> >> +
> >> +/* Perform the tlbi locally without broadcasting to other CPUs. */
> >> +#define TLBF_NOBROADCAST	((__force tlbf_t)BIT(3))
> >> +
> >> +static __always_inline void ___flush_tlb_range(struct vm_area_struct *vma,  
> > 
> > Can we come up with anything better for naming than more underscores?
> > 
> > My eyes skipped over there being 3 here rather than 2 and I got rather confused
> > as a result.  Maybe at least make it excessive and go from 2 to 4+?
> >   
> >> +					unsigned long start, unsigned long end,
> >> +					unsigned long stride, int tlb_level,
> >> +					tlbf_t flags)
> >>  {
> >> +	struct mm_struct *mm = vma->vm_mm;
> >>  	unsigned long asid, pages;
> >>  
> >> -	start = round_down(start, stride);
> >> -	end = round_up(end, stride);
> >>  	pages = (end - start) >> PAGE_SHIFT;
> >>  
> >>  	if (__flush_tlb_range_limit_excess(pages, stride)) {
> >> @@ -557,17 +574,41 @@ static inline void __flush_tlb_range_nosync(struct mm_struct *mm,
> >>  		return;
> >>  	}
> >>  
> >> -	dsb(ishst);
> >> +	if (!(flags & TLBF_NOBROADCAST))
> >> +		dsb(ishst);
> >> +	else
> >> +		dsb(nshst);
> >> +
> >>  	asid = ASID(mm);
> >>  
> >> -	if (flags & TLBF_NOWALKCACHE)
> >> -		__flush_s1_tlb_range_op(vale1is, start, pages, stride,
> >> -				     asid, tlb_level);
> >> -	else
> >> +	switch (flags & (TLBF_NOWALKCACHE | TLBF_NOBROADCAST)) {
> >> +	case TLBF_NONE:
> >>  		__flush_s1_tlb_range_op(vae1is, start, pages, stride,
> >> -				     asid, tlb_level);
> >> +					asid, tlb_level);
> >> +		break;
> >> +	case TLBF_NOWALKCACHE:
> >> +		__flush_s1_tlb_range_op(vale1is, start, pages, stride,
> >> +					asid, tlb_level);
> >> +		break;
> >> +	case TLBF_NOBROADCAST:
> >> +		__flush_s1_tlb_range_op(vae1, start, pages, stride,
> >> +					asid, tlb_level);
> >> +		break;
> >> +	case TLBF_NOWALKCACHE | TLBF_NOBROADCAST:
> >> +		__flush_s1_tlb_range_op(vale1, start, pages, stride,
> >> +					asid, tlb_level);
> >> +		break;
> >> +	}
> >> +
> >> +	if (!(flags & TLBF_NONOTIFY))
> >> +		mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);
> >>  
> >> -	mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);
> >> +	if (!(flags & TLBF_NOSYNC)) {
> >> +		if (!(flags & TLBF_NOBROADCAST))
> >> +			dsb(ish);
> >> +		else
> >> +			dsb(nsh);
> >> +	}
> >>  }
> >>  
> >>  static inline void __flush_tlb_range(struct vm_area_struct *vma,
> >> @@ -575,24 +616,9 @@ static inline void __flush_tlb_range(struct vm_area_struct *vma,
> >>  				     unsigned long stride, int tlb_level,
> >>  				     tlbf_t flags)
> >>  {
> >> -	__flush_tlb_range_nosync(vma->vm_mm, start, end, stride,
> >> -				 tlb_level, flags);
> >> -	dsb(ish);
> >> -}
> >> -
> >> -static inline void local_flush_tlb_contpte(struct vm_area_struct *vma,
> >> -					   unsigned long addr)
> >> -{
> >> -	unsigned long asid;
> >> -
> >> -	addr = round_down(addr, CONT_PTE_SIZE);
> >> -
> >> -	dsb(nshst);
> >> -	asid = ASID(vma->vm_mm);
> >> -	__flush_s1_tlb_range_op(vale1, addr, CONT_PTES, PAGE_SIZE, asid, 3);
> >> -	mmu_notifier_arch_invalidate_secondary_tlbs(vma->vm_mm, addr,
> >> -						    addr + CONT_PTE_SIZE);
> >> -	dsb(nsh);
> >> +	start = round_down(start, stride);
> >> +	end = round_up(end, stride);
> >> +	___flush_tlb_range(vma, start, end, stride, tlb_level, flags);
> >>  }
> >>  
> >>  static inline void flush_tlb_range(struct vm_area_struct *vma,
> >> @@ -645,7 +671,10 @@ static inline void __flush_tlb_kernel_pgtable(unsigned long kaddr)
> >>  static inline void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *batch,
> >>  		struct mm_struct *mm, unsigned long start, unsigned long end)
> >>  {
> >> -	__flush_tlb_range_nosync(mm, start, end, PAGE_SIZE, 3, TLBF_NOWALKCACHE);
> >> +	struct vm_area_struct vma = { .vm_mm = mm, .vm_flags = 0 };
> >> +
> >> +	__flush_tlb_range(&vma, start, end, PAGE_SIZE, 3,
> >> +			  TLBF_NOWALKCACHE | TLBF_NOSYNC);
> >>  }
> >>  
> >>  static inline bool __pte_flags_need_flush(ptdesc_t oldval, ptdesc_t newval)
> >> diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
> >> index 1a12bb728ee1..ec17a0e70415 100644
> >> --- a/arch/arm64/mm/contpte.c
> >> +++ b/arch/arm64/mm/contpte.c
> >> @@ -527,8 +527,8 @@ int contpte_ptep_clear_flush_young(struct vm_area_struct *vma,
> >>  		 * eliding the trailing DSB applies here.
> >>  		 */
> >>  		addr = ALIGN_DOWN(addr, CONT_PTE_SIZE);
> >> -		__flush_tlb_range_nosync(vma->vm_mm, addr, addr + CONT_PTE_SIZE,
> >> -					 PAGE_SIZE, 3, TLBF_NOWALKCACHE);
> >> +		__flush_tlb_range(vma, addr, addr + CONT_PTE_SIZE,
> >> +				  PAGE_SIZE, 3, TLBF_NOWALKCACHE | TLBF_NOSYNC);
> >>  	}
> >>  
> >>  	return young;
> >> @@ -623,7 +623,10 @@ int contpte_ptep_set_access_flags(struct vm_area_struct *vma,
> >>  			__ptep_set_access_flags(vma, addr, ptep, entry, 0);
> >>  
> >>  		if (dirty)
> >> -			local_flush_tlb_contpte(vma, start_addr);
> >> +			__flush_tlb_range(vma, start_addr,
> >> +					  start_addr + CONT_PTE_SIZE,
> >> +					  PAGE_SIZE, 3,
> >> +					  TLBF_NOWALKCACHE | TLBF_NOBROADCAST);
> >>  	} else {
> >>  		__contpte_try_unfold(vma->vm_mm, addr, ptep, orig_pte);
> >>  		__ptep_set_access_flags(vma, addr, ptep, entry, dirty);  
> >   
> 
>