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[95.203.6.24]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54963962fe4sm1070504e87.240.2025.03.05.09.27.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Mar 2025 09:27:51 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 5 Mar 2025 18:27:48 +0100 To: Ryosuke Yasuoka Cc: maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, kraxel@redhat.com, gurchetansingh@chromium.org, olvaffe@gmail.com, akpm@linux-foundation.org, urezki@gmail.com, hch@infradead.org, dmitry.osipenko@collabora.com, jfalempe@redhat.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-mm@kvack.org Subject: Re: [PATCH drm-next 1/2] vmalloc: Add atomic_vmap Message-ID: References: <20250305152555.318159-1-ryasuoka@redhat.com> <20250305152555.318159-2-ryasuoka@redhat.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250305152555.318159-2-ryasuoka@redhat.com> On Thu, Mar 06, 2025 at 12:25:53AM +0900, Ryosuke Yasuoka wrote: > Some drivers can use vmap in drm_panic, however, vmap is sleepable and > takes locks. Since drm_panic will vmap in panic handler, atomic_vmap > requests pages with GFP_ATOMIC and maps KVA without locks and sleep. > > Signed-off-by: Ryosuke Yasuoka > --- > include/linux/vmalloc.h | 2 + > mm/internal.h | 5 ++ > mm/vmalloc.c | 105 ++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 112 insertions(+) > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index 31e9ffd936e3..c7a2a9a1976d 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -190,6 +190,8 @@ void * __must_check vrealloc_noprof(const void *p, size_t size, gfp_t flags) > extern void vfree(const void *addr); > extern void vfree_atomic(const void *addr); > > +extern void *atomic_vmap(struct page **pages, unsigned int count, > + unsigned long flags, pgprot_t prot); > extern void *vmap(struct page **pages, unsigned int count, > unsigned long flags, pgprot_t prot); > void *vmap_pfn(unsigned long *pfns, unsigned int count, pgprot_t prot); > diff --git a/mm/internal.h b/mm/internal.h > index 109ef30fee11..134b332bf5b9 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1278,6 +1278,11 @@ int numa_migrate_check(struct folio *folio, struct vm_fault *vmf, > void free_zone_device_folio(struct folio *folio); > int migrate_device_coherent_folio(struct folio *folio); > > +struct vm_struct *atomic_get_vm_area_node(unsigned long size, unsigned long align, > + unsigned long shift, unsigned long flags, > + unsigned long start, unsigned long end, int node, > + gfp_t gfp_mask, const void *caller); > + > struct vm_struct *__get_vm_area_node(unsigned long size, > unsigned long align, unsigned long shift, > unsigned long flags, unsigned long start, > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index a6e7acebe9ad..f5c93779c60a 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1945,6 +1945,57 @@ static inline void setup_vmalloc_vm(struct vm_struct *vm, > va->vm = vm; > } > > +static struct vmap_area *atomic_alloc_vmap_area(unsigned long size, > + unsigned long align, > + unsigned long vstart, unsigned long vend, > + int node, gfp_t gfp_mask, > + unsigned long va_flags, struct vm_struct *vm) > +{ > + struct vmap_node *vn; > + struct vmap_area *va; > + unsigned long addr; > + > + if (unlikely(!size || offset_in_page(size) || !is_power_of_2(align))) > + return ERR_PTR(-EINVAL); > + > + if (unlikely(!vmap_initialized)) > + return ERR_PTR(-EBUSY); > + > + va = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node); > + if (unlikely(!va)) > + return ERR_PTR(-ENOMEM); > + > + /* > + * Only scan the relevant parts containing pointers to other objects > + * to avoid false negatives. > + */ > + kmemleak_scan_area(&va->rb_node, SIZE_MAX, gfp_mask); > + > + addr = __alloc_vmap_area(&free_vmap_area_root, &free_vmap_area_list, > + size, align, vstart, vend); > + > + trace_alloc_vmap_area(addr, size, align, vstart, vend, addr == vend); > + > + va->va_start = addr; > + va->va_end = addr + size; > + va->vm = NULL; > + va->flags = va_flags; > + > + vm->addr = (void *)va->va_start; > + vm->size = va_size(va); > + va->vm = vm; > + > + vn = addr_to_node(va->va_start); > + > + insert_vmap_area(va, &vn->busy.root, &vn->busy.head); > + > + BUG_ON(!IS_ALIGNED(va->va_start, align)); > + BUG_ON(va->va_start < vstart); > + BUG_ON(va->va_end > vend); > + > + return va; > +} > + > /* > * Allocate a region of KVA of the specified size and alignment, within the > * vstart and vend. If vm is passed in, the two will also be bound. > @@ -3106,6 +3157,33 @@ static void clear_vm_uninitialized_flag(struct vm_struct *vm) > vm->flags &= ~VM_UNINITIALIZED; > } > > +struct vm_struct *atomic_get_vm_area_node(unsigned long size, unsigned long align, > + unsigned long shift, unsigned long flags, > + unsigned long start, unsigned long end, int node, > + gfp_t gfp_mask, const void *caller) > +{ > + struct vmap_area *va; > + struct vm_struct *area; > + > + size = ALIGN(size, 1ul << shift); > + if (unlikely(!size)) > + return NULL; > + > + area = kzalloc_node(sizeof(*area), gfp_mask, node); > + if (unlikely(!area)) > + return NULL; > + > + size += PAGE_SIZE; > + area->flags = flags; > + area->caller = caller; > + > + va = atomic_alloc_vmap_area(size, align, start, end, node, gfp_mask, 0, area); > + if (IS_ERR(va)) > + return NULL; > + > + return area; > +} > + > struct vm_struct *__get_vm_area_node(unsigned long size, > unsigned long align, unsigned long shift, unsigned long flags, > unsigned long start, unsigned long end, int node, > @@ -3418,6 +3496,33 @@ void vunmap(const void *addr) > } > EXPORT_SYMBOL(vunmap); > > +void *atomic_vmap(struct page **pages, unsigned int count, > + unsigned long flags, pgprot_t prot) > +{ > + struct vm_struct *area; > + unsigned long addr; > + unsigned long size; /* In bytes */ > + > + if (count > totalram_pages()) > + return NULL; > + > + size = (unsigned long)count << PAGE_SHIFT; > + area = atomic_get_vm_area_node(size, 1, PAGE_SHIFT, flags, > + VMALLOC_START, VMALLOC_END, > + NUMA_NO_NODE, GFP_ATOMIC, > + __builtin_return_address(0)); > + if (!area) > + return NULL; > + > + addr = (unsigned long)area->addr; > + if (vmap_pages_range(addr, addr + size, pgprot_nx(prot), > + pages, PAGE_SHIFT) < 0) { > + return NULL; > + } > + > + return area->addr; > +} > + > /** > * vmap - map an array of pages into virtually contiguous space > * @pages: array of page pointers > -- > 2.48.1 > It is copy-paste code, so it is odd. The proposal is not a way forward to me. Unfortunately vmalloc is not compatible with GFP_ATOMIC, there is at least one place it is a page-table allocation entries where it is hard-coded to the GFP_KERNEL. Doing this without locks and synchronizations is not possible. -- Uladzislau Rezki