Re: [PATCH v2 5/6] mm: tlb: Provide flush_*_tlb_range wrappers
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2020-05-26 14:52:53
Also in:
linux-arch, linux-mm, lkml
On Mon, May 25, 2020 at 03:19:42PM +0800, Zhenyu Ye wrote:
On 2020/5/22 23:42, Catalin Marinas wrote:quoted
On Thu, Apr 23, 2020 at 09:56:55PM +0800, Zhenyu Ye wrote:quoted
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index 3d7c01e76efc..3eff199d3507 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c@@ -101,6 +101,28 @@ pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address, #ifdef CONFIG_TRANSPARENT_HUGEPAGE +#ifndef __HAVE_ARCH_FLUSH_PMD_TLB_RANGE + +#define FLUSH_Pxx_TLB_RANGE(_pxx) \ +void flush_##_pxx##_tlb_range(struct vm_area_struct *vma, \ + unsigned long addr, unsigned long end) \ +{ \ + struct mmu_gather tlb; \ + \ + tlb_gather_mmu(&tlb, vma->vm_mm, addr, end); \ + tlb_start_vma(&tlb, vma); \ + tlb_flush_##_pxx##_range(&tlb, addr, end - addr); \ + tlb_end_vma(&tlb, vma); \ + tlb_finish_mmu(&tlb, addr, end); \ +}I may have confused myself (flush_p??_tlb_* vs. tlb_flush_p??_*) but do actually need this whole tlb_gather thing here? IIUC (by grep'ing), flush_p?d_tlb_range() is only called on huge pages, so we should know the level already.tlb_flush_##_pxx##_range() is used to set tlb->cleared_*, flush_##_pxx##_tlb_range() will actually flush the TLB entry. In arch64, tlb_flush_p?d_range() is defined as: #define flush_pmd_tlb_range(vma, addr, end) flush_tlb_range(vma, addr, end) #define flush_pud_tlb_range(vma, addr, end) flush_tlb_range(vma, addr, end)
Currently, flush_p??_tlb_range() are generic and defined as above. I think in the generic code they can remain an alias for flush_tlb_range(). On arm64, we can redefine them as: #define flush_pte_tlb_range(vma, addr, end) __flush_tlb_range(vma, addr, end, 3) #define flush_pmd_tlb_range(vma, addr, end) __flush_tlb_range(vma, addr, end, 2) #define flush_pud_tlb_range(vma, addr, end) __flush_tlb_range(vma, addr, end, 1) #define flush_p4d_tlb_range(vma, addr, end) __flush_tlb_range(vma, addr, end, 0) (unless the compiler optimises away all the mmu_gather stuff in your macro above but they don't look trivial to me) Also, I don't see the new flush_pte_* and flush_p4d_* macros used anywhere and I don't think they are needed. The pte equivalent is flush_tlb_page() (we need to make sure it's not used on a pmd in the hugetlb context).
So even if we know the level here, we can not pass the value to tlbi instructions (flush_tlb_range() is a common kernel interface and retro-fit it needs lots of changes), according to Peter's suggestion, I finally decide to pass the value of TTL by the tlb_gather_* frame.[1]
My comment was about the generic implementation using mmu_gather as you are proposing. We don't need to change the flush_tlb_range() interface, nor do we need to rewrite flush_p??_tlb_range(). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel