Hi Dave,
John David Anglin <dave.anglin@xxxxxxxx> writes:
> When a page is not present, we get non-access data TLB faults from
> the fdc and fic instructions in flush_user_dcache_range_asm and
> flush_user_icache_range_asm. When these occur, the cache line is
> not invalidated and potentially we get memory corruption. The
> problem was hidden by the nullification of the flush instructions.
>
> These faults also affect performance. With pa8800/pa8900 processors,
> there will be 32 faults per 4 KB page since the cache line is 128
> bytes. The will be more faults with earlier processors.
>
> The problem is fixed by using flush_cache_pages(). It does the flush
> using a tmp alias mapping.
>
> The flush_cache_pages() call in flush_cache_range() flushed too
> large a range.
>
> Signed-off-by: John David Anglin <dave.anglin@xxxxxxxx>
> ---
>
> diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
> index 94150b91c96f..e439b53b0f62 100644
> --- a/arch/parisc/kernel/cache.c
> +++ b/arch/parisc/kernel/cache.c
> @@ -558,15 +558,6 @@ static void flush_cache_pages(struct vm_area_struct *vma, struct mm_struct *mm,
> }
> }
>
> -static void flush_user_cache_tlb(struct vm_area_struct *vma,
> - unsigned long start, unsigned long end)
> -{
> - flush_user_dcache_range_asm(start, end);
> - if (vma->vm_flags & VM_EXEC)
> - flush_user_icache_range_asm(start, end);
> - flush_tlb_range(vma, start, end);
> -}
> -
> void flush_cache_mm(struct mm_struct *mm)
> {
> struct vm_area_struct *vma;
> @@ -582,13 +573,6 @@ void flush_cache_mm(struct mm_struct *mm)
> }
>
> preempt_disable();
> - if (mm->context == mfsp(3)) {
> - for (vma = mm->mmap; vma; vma = vma->vm_next)
> - flush_user_cache_tlb(vma, vma->vm_start, vma->vm_end);
> - preempt_enable();
> - return;
> - }
> -
> for (vma = mm->mmap; vma; vma = vma->vm_next)
> flush_cache_pages(vma, mm, vma->vm_start, vma->vm_end);
> preempt_enable();
> @@ -606,13 +590,7 @@ void flush_cache_range(struct vm_area_struct *vma,
> }
>
> preempt_disable();
> - if (vma->vm_mm->context == mfsp(3)) {
> - flush_user_cache_tlb(vma, start, end);
> - preempt_enable();
> - return;
> - }
> -
> - flush_cache_pages(vma, vma->vm_mm, vma->vm_start, vma->vm_end);
> + flush_cache_pages(vma, vma->vm_mm, start, end);
> preempt_enable();
> }
>
I think the preempt_enable()/disable() calls are no longer
required. I've added them to fix a bug when the kernel is preempted
after the mm->context / mfsp(3) compare but as that is now removed
this shouldn't be required anymore.
