From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [RFC][PATCH 05/11] asm-generic/tlb: Provide generic tlb_flush Date: Thu, 13 Sep 2018 16:06:21 +0200 Message-ID: <20180913140621.GY24124@hirez.programming.kicks-ass.net> References: <20180913092110.817204997@infradead.org> <20180913092812.132208484@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Jann Horn Cc: Will Deacon , "Aneesh Kumar K.V" , Andrew Morton , npiggin@gmail.com, linux-arch , Linux-MM , kernel list , Russell King - ARM Linux , Heiko Carstens List-Id: linux-arch.vger.kernel.org On Thu, Sep 13, 2018 at 03:09:47PM +0200, Jann Horn wrote: > On Thu, Sep 13, 2018 at 3:01 PM Peter Zijlstra 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); From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:58332 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730009AbeIMTQN (ORCPT ); Thu, 13 Sep 2018 15:16:13 -0400 Date: Thu, 13 Sep 2018 16:06:21 +0200 From: Peter Zijlstra Subject: Re: [RFC][PATCH 05/11] asm-generic/tlb: Provide generic tlb_flush Message-ID: <20180913140621.GY24124@hirez.programming.kicks-ass.net> References: <20180913092110.817204997@infradead.org> <20180913092812.132208484@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Jann Horn Cc: Will Deacon , "Aneesh Kumar K.V" , Andrew Morton , npiggin@gmail.com, linux-arch , Linux-MM , kernel list , Russell King - ARM Linux , Heiko Carstens Message-ID: <20180913140621.2XN4Ca0FYC-OtXacIqnzJpVzzCTES5bP3pm7gX6N1Go@z> On Thu, Sep 13, 2018 at 03:09:47PM +0200, Jann Horn wrote: > On Thu, Sep 13, 2018 at 3:01 PM Peter Zijlstra 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);