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[90.233.213.186]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-2ef24fbe937sm15017101fa.6.2024.07.24.07.32.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jul 2024 07:32:40 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 24 Jul 2024 16:32:37 +0200 To: Adrian Huang Cc: urezki@gmail.com, ahuang12@lenovo.com, akpm@linux-foundation.org, hch@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, peterz@infradead.org, sunjw10@lenovo.com Subject: Re: [PATCH 1/1] mm/vmalloc: Add preempt point in purge_vmap_node() when enabling kasan Message-ID: References: <20240724124624.27673-1-ahuang12@lenovo.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240724124624.27673-1-ahuang12@lenovo.com> On Wed, Jul 24, 2024 at 08:46:24PM +0800, Adrian Huang wrote: > > It works great and does not generate the soft-lock-up splat :) > > See below some comments: > > Great. Thanks for the confirmation. > > > > >> + kasan_release_vmalloc(start, end, start, end, KASAN_VMALLOC_TLB_FLUSH); > >> + > >> > > Do we need it here? We just did the TLB flush for en entire range in the > > __purge_vmap_area_lazy(). So, it is two times invoked and looks odd to me. > > > > Am i missing something? > > 1. The TLB flush for the entire range in __purge_vmap_area_lazy() is for > the vmalloc virtual address (VMALLOC_START->VMALLOC_END). > > 2. The TLB flush in purge_vmap_node() is for the KASAN shadow virtual address > (the shadow offset 'CONFIG_KASAN_SHADOW_OFFSET' is defined in .config). > Correct. It deals with a shadow region! > > BTW, I found my first patch has the potential risk. We need to flush TLB of > the KASAN shadow virtual address firstly. Please see the following patch for > detail. (I put the comment in the following patch). The following patch > also works well on my 256-core machine. > I noticed that and it would be my second question :) > > If you're ok with the patch, I'll submit it for upstream review. And, may I > have your tag(s): tested-by/reviewed-by? (If possible, could you please have > a test for the following patch). > I am OK. I will test and get back soon. > Thanks. > > --- > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index 70d6a8f6e25d..ddbf42a1a7b7 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h > @@ -55,6 +55,9 @@ extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D]; > int kasan_populate_early_shadow(const void *shadow_start, > const void *shadow_end); > > +#define KASAN_VMALLOC_PAGE_RANGE 0x1 /* Apply exsiting page range */ > +#define KASAN_VMALLOC_TLB_FLUSH 0x2 /* TLB flush */ > + > #ifndef kasan_mem_to_shadow > static inline void *kasan_mem_to_shadow(const void *addr) > { > @@ -511,7 +514,8 @@ void kasan_populate_early_vm_area_shadow(void *start, unsigned long size); > int kasan_populate_vmalloc(unsigned long addr, unsigned long size); > void kasan_release_vmalloc(unsigned long start, unsigned long end, > unsigned long free_region_start, > - unsigned long free_region_end); > + unsigned long free_region_end, > + unsigned long flags); > > #else /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ > > @@ -526,7 +530,8 @@ static inline int kasan_populate_vmalloc(unsigned long start, > static inline void kasan_release_vmalloc(unsigned long start, > unsigned long end, > unsigned long free_region_start, > - unsigned long free_region_end) { } > + unsigned long free_region_end, > + unsigned long flags) { } > > #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ > > @@ -561,7 +566,8 @@ static inline int kasan_populate_vmalloc(unsigned long start, > static inline void kasan_release_vmalloc(unsigned long start, > unsigned long end, > unsigned long free_region_start, > - unsigned long free_region_end) { } > + unsigned long free_region_end, > + unsigned long flags) { } > > static inline void *kasan_unpoison_vmalloc(const void *start, > unsigned long size, > diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c > index d6210ca48dda..88d1c9dcb507 100644 > --- a/mm/kasan/shadow.c > +++ b/mm/kasan/shadow.c > @@ -489,7 +489,8 @@ static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr, > */ > void kasan_release_vmalloc(unsigned long start, unsigned long end, > unsigned long free_region_start, > - unsigned long free_region_end) > + unsigned long free_region_end, > + unsigned long flags) > { > void *shadow_start, *shadow_end; > unsigned long region_start, region_end; > @@ -522,12 +523,17 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end, > __memset(shadow_start, KASAN_SHADOW_INIT, shadow_end - shadow_start); > return; > } > - apply_to_existing_page_range(&init_mm, > + > + > + if (flags & KASAN_VMALLOC_PAGE_RANGE) > + apply_to_existing_page_range(&init_mm, > (unsigned long)shadow_start, > size, kasan_depopulate_vmalloc_pte, > NULL); > - flush_tlb_kernel_range((unsigned long)shadow_start, > - (unsigned long)shadow_end); > + > + if (flags & KASAN_VMALLOC_TLB_FLUSH) > + flush_tlb_kernel_range((unsigned long)shadow_start, > + (unsigned long)shadow_end); > } > } > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index e34ea860153f..12cdc92cdb83 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2193,8 +2193,22 @@ static void purge_vmap_node(struct work_struct *work) > struct vmap_area *va, *n_va; > LIST_HEAD(local_list); > > + unsigned long start; > + unsigned long end; > + > vn->nr_purged = 0; > > + start = list_first_entry(&vn->purge_list, struct vmap_area, list)->va_start; > + > + end = list_last_entry(&vn->purge_list, struct vmap_area, list)->va_end; > + > + /* > + * Since node_pool_add_va() returns vmap_area(s) to its pool, the > + * returned vmap_area(s) might be grabbed immediately via node_alloc() > + * by other core. We need to flush TLB firstly. > + */ > + kasan_release_vmalloc(start, end, start, end, KASAN_VMALLOC_TLB_FLUSH); > + > list_for_each_entry_safe(va, n_va, &vn->purge_list, list) { > unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT; > unsigned long orig_start = va->va_start; > @@ -2205,7 +2219,8 @@ static void purge_vmap_node(struct work_struct *work) > > if (is_vmalloc_or_module_addr((void *)orig_start)) > kasan_release_vmalloc(orig_start, orig_end, > - va->va_start, va->va_end); > + va->va_start, va->va_end, > + KASAN_VMALLOC_PAGE_RANGE); > > atomic_long_sub(nr, &vmap_lazy_nr); > vn->nr_purged++; > @@ -4726,7 +4741,8 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, > &free_vmap_area_list); > if (va) > kasan_release_vmalloc(orig_start, orig_end, > - va->va_start, va->va_end); > + va->va_start, va->va_end, > + KASAN_VMALLOC_PAGE_RANGE | KASAN_VMALLOC_TLB_FLUSH); > vas[area] = NULL; > } > > @@ -4776,7 +4792,8 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, > &free_vmap_area_list); > if (va) > kasan_release_vmalloc(orig_start, orig_end, > - va->va_start, va->va_end); > + va->va_start, va->va_end, > + KASAN_VMALLOC_PAGE_RANGE | KASAN_VMALLOC_TLB_FLUSH); > vas[area] = NULL; > kfree(vms[area]); > }