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b=LpgVnwBSDBMv2ZCVDsEcjfQRjXldbcrdFN6YWC0rquZ76JA4WLAVGYdrU2Hg0J0lu b9l48jH/dtdOxXSdPpiNOqWudkX7H+Dmk6Tu9z2LXgLyILK31qQOLW7KZ2lLLYAx3I fUYlaYaQdJ3iXTb1M1TogOngIKpo02yqpbd2QnvxpVH038t+JW9MFZDkhAV1DQCDii dOyl2XK8+BhGI4nDZpgsWPVpoFWUOyBIbuadfyTaVSYMIvySJTlLYbadUiM4xtF7KN 8RLN2HjeI1uJyOM2NAk8ouza4Wv8Bl+HS7G4okRB0cqcK7sKPLJJVHjh9v1hcoxnp2 dAjEYyWjWwq7A== Date: Fri, 5 Jun 2026 12:31:52 +0100 From: Lorenzo Stoakes To: Dev Jain Cc: akpm@linux-foundation.org, liam@infradead.org, jgg@ziepe.ca, leon@kernel.org, david@kernel.org, shuah@kernel.org, vbabka@kernel.org, jannh@google.com, pfalcato@suse.de, balbirs@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-kselftest@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, usama.arif@linux.dev Subject: Re: [PATCH v3 2/2] selftests/mm/hmm-tests: test pagemap reads of PMD device-private entries Message-ID: References: <20260604055308.1947679-1-dev.jain@arm.com> <20260604055308.1947679-3-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260604055308.1947679-3-dev.jain@arm.com> X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 86FFA18000C X-Stat-Signature: u34coj5zz9gczxumbmsy8jqdp6j3or7h X-HE-Tag: 1780659121-48684 X-HE-Meta: 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 xcK3tR3a iJsYJsWFzoppuDM8nMFzS34o5Bu7XSEPIqYeeB2CoBDsNNPAyJ/IFvaFDsiVyFVvXxNUVyiHrbBgiPmrATN+Fqh+y5dqUyupPsyADJzge71ELGg4/D6emxuFl7q2ew/QP23i+v5ieLWRmvGXQcuX7vl2+9w5QOo4bEAPJ0/3guEqbeqSFWp9RXQcYjBkYNonNW5ZWoz8dsXZunqd1+NXcmJ63ksPgsBh5SGpkPGwzYSD20BrmnPLqvh7F/r+cLgPP1b4jvrQh1hX8vNdN246veWQ5o0w47EF+gswungeiQZTw1qwl6XXc9+JpmwZZGd5EOe6ZYB5WjcmxnW9Pkd4XsyfWHw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 04, 2026 at 05:53:06AM +0000, Dev Jain wrote: > To cover pagemap paths scanning PMD entries, add assertions to check > whether a device-private PMD entry has the correct pagemap information - > the PM_SWAP bit must be on in the pagemap entry. Before that, we must > assert through HMM_DMIRROR_SNAPSHOT snapshot that the leaf entry is > at PMD level and not PTE level. > > Signed-off-by: Dev Jain LGTM, and confirmed this triggers the issue locally so: Reviewed-by: Lorenzo Stoakes > --- > tools/testing/selftests/mm/hmm-tests.c | 34 ++++++++++++++++++++++++-- > 1 file changed, 32 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c > index e1c8a679a4cf3..46e0c8c921c3d 100644 > --- a/tools/testing/selftests/mm/hmm-tests.c > +++ b/tools/testing/selftests/mm/hmm-tests.c > @@ -2276,8 +2276,11 @@ TEST_F(hmm, migrate_anon_huge_fault) > unsigned long npages; > unsigned long size; > unsigned long i; > + unsigned char *m; > + uint64_t entry; > void *old_ptr; > void *map; > + int pagemap_fd; > int *ptr; > int ret; > > @@ -2300,8 +2303,6 @@ TEST_F(hmm, migrate_anon_huge_fault) > > npages = size >> self->page_shift; > map = (void *)ALIGN((uintptr_t)buffer->ptr, size); > - ret = madvise(map, size, MADV_HUGEPAGE); > - ASSERT_EQ(ret, 0); > old_ptr = buffer->ptr; > buffer->ptr = map; > > @@ -2309,6 +2310,9 @@ TEST_F(hmm, migrate_anon_huge_fault) > for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) > ptr[i] = i; > > + ret = madvise(map, size, MADV_COLLAPSE); > + ASSERT_EQ(ret, 0); > + > /* Migrate memory to device. */ > ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages); > ASSERT_EQ(ret, 0); > @@ -2318,6 +2322,32 @@ TEST_F(hmm, migrate_anon_huge_fault) > for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i) > ASSERT_EQ(ptr[i], i); > > + if (!hmm_is_coherent_type(variant->device_number)) { > + ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, > + buffer, npages); > + ASSERT_EQ(ret, 0); > + ASSERT_EQ(buffer->cpages, npages); > + > + m = buffer->mirror; > + for (i = 0; i < npages; ++i) > + ASSERT_EQ(m[i], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL | > + HMM_DMIRROR_PROT_WRITE | > + HMM_DMIRROR_PROT_PMD); > + > + pagemap_fd = open("/proc/self/pagemap", O_RDONLY); > + ASSERT_GE(pagemap_fd, 0); > + > + for (i = 0; i < npages; ++i) { > + entry = pagemap_get_entry(pagemap_fd, > + (char *)buffer->ptr + i * self->page_size); > + > + ASSERT_NE(entry & PM_SWAP, 0); > + ASSERT_FALSE(PAGEMAP_PRESENT(entry)); > + } > + > + close(pagemap_fd); > + } > + > /* Fault pages back to system memory and check them. */ > for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) > ASSERT_EQ(ptr[i], i); > -- > 2.43.0 >