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Mon, 27 Nov 2023 21:39:28 -0800 (PST) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20231119165721.9849-1-alexandru.elisei@arm.com> <20231119165721.9849-22-alexandru.elisei@arm.com> In-Reply-To: <20231119165721.9849-22-alexandru.elisei@arm.com> From: Peter Collingbourne Date: Mon, 27 Nov 2023 21:39:17 -0800 Message-ID: Subject: Re: [PATCH RFC v2 21/27] mm: arm64: Handle tag storage pages mapped before mprotect(PROT_MTE) To: Alexandru Elisei Cc: catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev, maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, arnd@arndb.de, akpm@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, mhiramat@kernel.org, rppt@kernel.org, hughd@google.com, steven.price@arm.com, anshuman.khandual@arm.com, vincenzo.frascino@arm.com, david@redhat.com, eugenis@google.com, kcc@google.com, hyesoo.yu@samsung.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Alexandru, On Sun, Nov 19, 2023 at 8:59=E2=80=AFAM Alexandru Elisei wrote: > > Signed-off-by: Alexandru Elisei > --- > arch/arm64/include/asm/mte_tag_storage.h | 1 + > arch/arm64/kernel/mte_tag_storage.c | 15 +++++++ > arch/arm64/mm/fault.c | 55 ++++++++++++++++++++++++ > include/linux/migrate.h | 8 +++- > include/linux/migrate_mode.h | 1 + > mm/internal.h | 6 --- > 6 files changed, 78 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/include/asm/mte_tag_storage.h b/arch/arm64/includ= e/asm/mte_tag_storage.h > index b97406d369ce..6a8b19a6a758 100644 > --- a/arch/arm64/include/asm/mte_tag_storage.h > +++ b/arch/arm64/include/asm/mte_tag_storage.h > @@ -33,6 +33,7 @@ int reserve_tag_storage(struct page *page, int order, g= fp_t gfp); > void free_tag_storage(struct page *page, int order); > > bool page_tag_storage_reserved(struct page *page); > +bool page_is_tag_storage(struct page *page); > > vm_fault_t handle_page_missing_tag_storage(struct vm_fault *vmf); > vm_fault_t handle_huge_page_missing_tag_storage(struct vm_fault *vmf); > diff --git a/arch/arm64/kernel/mte_tag_storage.c b/arch/arm64/kernel/mte_= tag_storage.c > index a1cc239f7211..5096ce859136 100644 > --- a/arch/arm64/kernel/mte_tag_storage.c > +++ b/arch/arm64/kernel/mte_tag_storage.c > @@ -500,6 +500,21 @@ bool page_tag_storage_reserved(struct page *page) > return test_bit(PG_tag_storage_reserved, &page->flags); > } > > +bool page_is_tag_storage(struct page *page) > +{ > + unsigned long pfn =3D page_to_pfn(page); > + struct range *tag_range; > + int i; > + > + for (i =3D 0; i < num_tag_regions; i++) { > + tag_range =3D &tag_regions[i].tag_range; > + if (tag_range->start <=3D pfn && pfn <=3D tag_range->end) > + return true; > + } > + > + return false; > +} > + > int reserve_tag_storage(struct page *page, int order, gfp_t gfp) > { > unsigned long start_block, end_block; > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 6730a0812a24..964c5ae161a3 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -12,6 +12,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -956,6 +957,50 @@ void tag_clear_highpage(struct page *page) > } > > #ifdef CONFIG_ARM64_MTE_TAG_STORAGE > + > +#define MR_TAGGED_TAG_STORAGE MR_ARCH_1 > + > +extern bool isolate_lru_page(struct page *page); > +extern void putback_movable_pages(struct list_head *l); Could we move these declarations to a non-mm-internal header and #include it instead of manually declaring them here? > + > +/* Returns with the page reference dropped. */ > +static void migrate_tag_storage_page(struct page *page) > +{ > + struct migration_target_control mtc =3D { > + .nid =3D NUMA_NO_NODE, > + .gfp_mask =3D GFP_HIGHUSER_MOVABLE | __GFP_TAGGED, > + }; > + unsigned long i, nr_pages =3D compound_nr(page); > + LIST_HEAD(pagelist); > + int ret, tries; > + > + lru_cache_disable(); > + > + for (i =3D 0; i < nr_pages; i++) { > + if (!isolate_lru_page(page + i)) { > + ret =3D -EAGAIN; > + goto out; > + } > + /* Isolate just grabbed another reference, drop ours. */ > + put_page(page + i); > + list_add_tail(&(page + i)->lru, &pagelist); > + } > + > + tries =3D 5; > + while (tries--) { > + ret =3D migrate_pages(&pagelist, alloc_migration_target, = NULL, (unsigned long)&mtc, > + MIGRATE_SYNC, MR_TAGGED_TAG_STORAGE, = NULL); > + if (ret =3D=3D 0 || ret !=3D -EBUSY) This could be simplified to: if (ret !=3D -EBUSY) Peter