| Message ID | 20180913092812.132208484@infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | my generic mmu_gather patches | expand |
On Thu, Sep 13, 2018 at 3:01 PM Peter Zijlstra <peterz@infradead.org> wrote: > Provide a generic tlb_flush() implementation that relies on > flush_tlb_range(). This is a little awkward because flush_tlb_range() > assumes a VMA for range invalidation, but we no longer have one. > > Audit of all flush_tlb_range() implementations shows only vma->vm_mm > and vma->vm_flags are used, and of the latter only VM_EXEC (I-TLB > invalidates) and VM_HUGETLB (large TLB invalidate) are used. > > Therefore, track VM_EXEC and VM_HUGETLB in two more bits, and create a > 'fake' VMA. > > This allows architectures that have a reasonably efficient > flush_tlb_range() to not require any additional effort. [...] > +#define tlb_flush tlb_flush > +static inline void tlb_flush(struct mmu_gather *tlb) > +{ > + if (tlb->fullmm || tlb->need_flush_all) { > + flush_tlb_mm(tlb->mm); > + } else { > + struct vm_area_struct vma = { > + .vm_mm = tlb->mm, > + .vm_flags = tlb->vma_exec ? VM_EXEC : 0 | > + tlb->vma_huge ? VM_HUGETLB : 0, This looks wrong to me. Bitwise OR has higher precedence than the ternary operator, so I think this code is equivalent to: .vm_flags = tlb->vma_exec ? VM_EXEC : (0 | tlb->vma_huge) ? VM_HUGETLB : 0 meaning that executable+huge mappings would only get VM_EXEC, but not VM_HUGETLB. > + }; > + > + flush_tlb_range(&vma, tlb->start, tlb->end); > + } > } > +#endif
On Thu, Sep 13, 2018 at 03:09:47PM +0200, Jann Horn wrote: > On Thu, Sep 13, 2018 at 3:01 PM Peter Zijlstra <peterz@infradead.org> wrote: > > Provide a generic tlb_flush() implementation that relies on > > flush_tlb_range(). This is a little awkward because flush_tlb_range() > > assumes a VMA for range invalidation, but we no longer have one. > > > > Audit of all flush_tlb_range() implementations shows only vma->vm_mm > > and vma->vm_flags are used, and of the latter only VM_EXEC (I-TLB > > invalidates) and VM_HUGETLB (large TLB invalidate) are used. > > > > Therefore, track VM_EXEC and VM_HUGETLB in two more bits, and create a > > 'fake' VMA. > > > > This allows architectures that have a reasonably efficient > > flush_tlb_range() to not require any additional effort. > [...] > > +#define tlb_flush tlb_flush > > +static inline void tlb_flush(struct mmu_gather *tlb) > > +{ > > + if (tlb->fullmm || tlb->need_flush_all) { > > + flush_tlb_mm(tlb->mm); > > + } else { > > + struct vm_area_struct vma = { > > + .vm_mm = tlb->mm, > > + .vm_flags = tlb->vma_exec ? VM_EXEC : 0 | > > + tlb->vma_huge ? VM_HUGETLB : 0, > > This looks wrong to me. Bitwise OR has higher precedence than the > ternary operator, so I think this code is equivalent to: > > .vm_flags = tlb->vma_exec ? VM_EXEC : (0 | tlb->vma_huge) ? VM_HUGETLB : 0 > > meaning that executable+huge mappings would only get VM_EXEC, but not > VM_HUGETLB. Bah. Fixed that. Thanks! --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -309,8 +309,8 @@ static inline void tlb_flush(struct mmu_ } else { struct vm_area_struct vma = { .vm_mm = tlb->mm, - .vm_flags = tlb->vma_exec ? VM_EXEC : 0 | - tlb->vma_huge ? VM_HUGETLB : 0, + .vm_flags = (tlb->vma_exec ? VM_EXEC : 0) | + (tlb->vma_huge ? VM_HUGETLB : 0), }; flush_tlb_range(&vma, tlb->start, tlb->end);
--- a/arch/arm64/include/asm/tlb.h +++ b/arch/arm64/include/asm/tlb.h @@ -27,6 +27,7 @@ static inline void __tlb_remove_table(vo free_page_and_swap_cache((struct page *)_table); } +#define tlb_flush tlb_flush static void tlb_flush(struct mmu_gather *tlb); #include <asm-generic/tlb.h> --- a/arch/powerpc/include/asm/tlb.h +++ b/arch/powerpc/include/asm/tlb.h @@ -28,6 +28,7 @@ #define tlb_end_vma(tlb, vma) do { } while (0) #define __tlb_remove_tlb_entry __tlb_remove_tlb_entry +#define tlb_flush tlb_flush extern void tlb_flush(struct mmu_gather *tlb); /* Get the generic bits... */ --- a/arch/riscv/include/asm/tlb.h +++ b/arch/riscv/include/asm/tlb.h @@ -18,6 +18,7 @@ struct mmu_gather; static void tlb_flush(struct mmu_gather *tlb); +#define tlb_flush tlb_flush #include <asm-generic/tlb.h> static inline void tlb_flush(struct mmu_gather *tlb) --- a/arch/x86/include/asm/tlb.h +++ b/arch/x86/include/asm/tlb.h @@ -6,6 +6,7 @@ #define tlb_end_vma(tlb, vma) do { } while (0) #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0) +#define tlb_flush tlb_flush static inline void tlb_flush(struct mmu_gather *tlb); #include <asm-generic/tlb.h> --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -241,6 +241,12 @@ struct mmu_gather { unsigned int cleared_puds : 1; unsigned int cleared_p4ds : 1; + /* + * tracks VM_EXEC | VM_HUGETLB in tlb_start_vma + */ + unsigned int vma_exec : 1; + unsigned int vma_huge : 1; + unsigned int batch_count; struct mmu_gather_batch *active; @@ -282,7 +288,35 @@ static inline void __tlb_reset_range(str tlb->cleared_pmds = 0; tlb->cleared_puds = 0; tlb->cleared_p4ds = 0; + /* + * Do not reset mmu_gather::vma_* fields here, we do not + * call into tlb_start_vma() again to set them if there is an + * intermediate flush. + */ +} + +#ifndef tlb_flush + +#if defined(tlb_start_vma) || defined(tlb_end_vma) +#error Default tlb_flush() relies on default tlb_start_vma() and tlb_end_vma() +#endif + +#define tlb_flush tlb_flush +static inline void tlb_flush(struct mmu_gather *tlb) +{ + if (tlb->fullmm || tlb->need_flush_all) { + flush_tlb_mm(tlb->mm); + } else { + struct vm_area_struct vma = { + .vm_mm = tlb->mm, + .vm_flags = tlb->vma_exec ? VM_EXEC : 0 | + tlb->vma_huge ? VM_HUGETLB : 0, + }; + + flush_tlb_range(&vma, tlb->start, tlb->end); + } } +#endif static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb) { @@ -353,19 +387,45 @@ static inline unsigned long tlb_get_unma * the vmas are adjusted to only cover the region to be torn down. */ #ifndef tlb_start_vma -#define tlb_start_vma(tlb, vma) \ -do { \ - if (!tlb->fullmm) \ - flush_cache_range(vma, vma->vm_start, vma->vm_end); \ -} while (0) +#define tlb_start_vma tlb_start_vma +static inline void tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct *vma) +{ + if (tlb->fullmm) + return; + + /* + * flush_tlb_range() implementations that look at VM_HUGETLB (tile, + * mips-4k) flush only large pages. + * + * flush_tlb_range() implementations that flush I-TLB also flush D-TLB + * (tile, xtensa, arm), so it's ok to just add VM_EXEC to an existing + * range. + * + * We rely on tlb_end_vma() to issue a flush, such that when we reset + * these values the batch is empty. + */ + tlb->vma_huge = !!(vma->vm_flags & VM_HUGETLB); + tlb->vma_exec = !!(vma->vm_flags & VM_EXEC); + + flush_cache_range(vma, vma->vm_start, vma->vm_end); +} #endif #ifndef tlb_end_vma -#define tlb_end_vma(tlb, vma) \ -do { \ - if (!tlb->fullmm) \ - tlb_flush_mmu_tlbonly(tlb); \ -} while (0) +#define tlb_end_vma tlb_end_vma +static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma) +{ + if (tlb->fullmm) + return; + + /* + * Do a TLB flush and reset the range at VMA boundaries; this avoids + * the ranges growing with the unused space between consecutive VMAs, + * but also the mmu_gather::vma_* flags from tlb_start_vma() rely on + * this. + */ + tlb_flush_mmu_tlbonly(tlb); +} #endif #ifndef __tlb_remove_tlb_entry
Provide a generic tlb_flush() implementation that relies on flush_tlb_range(). This is a little awkward because flush_tlb_range() assumes a VMA for range invalidation, but we no longer have one. Audit of all flush_tlb_range() implementations shows only vma->vm_mm and vma->vm_flags are used, and of the latter only VM_EXEC (I-TLB invalidates) and VM_HUGETLB (large TLB invalidate) are used. Therefore, track VM_EXEC and VM_HUGETLB in two more bits, and create a 'fake' VMA. This allows architectures that have a reasonably efficient flush_tlb_range() to not require any additional effort. Cc: Will Deacon <will.deacon@arm.com> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Nick Piggin <npiggin@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/arm64/include/asm/tlb.h | 1 arch/powerpc/include/asm/tlb.h | 1 arch/riscv/include/asm/tlb.h | 1 arch/x86/include/asm/tlb.h | 1 include/asm-generic/tlb.h | 80 +++++++++++++++++++++++++++++++++++------ 5 files changed, 74 insertions(+), 10 deletions(-)