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Mon, 09 Mar 2026 15:00:49 -0700 (PDT) From: Gabriel Brookman Date: Mon, 09 Mar 2026 17:59:39 -0400 Subject: [PATCH v4 07/13] target/arm: ldg on canonical tag loads the tag MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260309-feat-mte4-v4-7-daaf0375620d@gmail.com> References: <20260309-feat-mte4-v4-0-daaf0375620d@gmail.com> In-Reply-To: <20260309-feat-mte4-v4-0-daaf0375620d@gmail.com> To: qemu-devel@nongnu.org Cc: Peter Maydell , Gustavo Romero , Richard Henderson , qemu-arm@nongnu.org, Laurent Vivier , Pierrick Bouvier , Gabriel Brookman X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1773093641; l=2624; i=brookmangabriel@gmail.com; s=20251009; h=from:subject:message-id; bh=LIQLbnOi9t8oJGXDiTdEoadrMQhotgUGSWP3ejz82kI=; b=gkb8ojaplKj6LJ0PS7Fm3XshQONlr2JmX3LD2TRbny7CkKRHXA9oRapoN4qFs3sp/AromSCJ1 OMUnpfz5i0MBiTK72zIbq+9J971/D1mAZImILhlpMCSosjYW03zbHDb X-Developer-Key: i=brookmangabriel@gmail.com; a=ed25519; pk=m9TtPDal6WzoHNnQiHHKf8dTrv3DUCPUUTujuo8vNrw= Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::b136; envelope-from=brookmangabriel@gmail.com; helo=mail-yx1-xb136.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @gmail.com) X-ZM-MESSAGEID: 1773093737317158500 According to ARM ARM, section "Memory Tagging Region Types", loading tags from canonically tagged regions should use the canonical tags, not allocation tags. Signed-off-by: Gabriel Brookman --- target/arm/tcg/mte_helper.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/target/arm/tcg/mte_helper.c b/target/arm/tcg/mte_helper.c index b54fbd11c0..07797aecf9 100644 --- a/target/arm/tcg/mte_helper.c +++ b/target/arm/tcg/mte_helper.c @@ -313,6 +313,11 @@ uint64_t HELPER(ldg)(CPUARMState *env, uint64_t ptr, u= int64_t xt) /* Load if page supports tags. */ if (mem) { rtag =3D load_tag1(ptr, mem); + } else { + uint64_t bit55 =3D extract64(ptr, 55, 1); + if (canonical_tagging_enabled(env, bit55)) { + rtag =3D 0xF * bit55; + } } =20 return address_with_allocation_tag(xt, rtag); @@ -463,8 +468,10 @@ uint64_t HELPER(ldgm)(CPUARMState *env, uint64_t ptr) void *tag_mem; uint64_t ret; int shift; + bool bit55; =20 ptr =3D QEMU_ALIGN_DOWN(ptr, gm_bs_bytes); + bit55 =3D extract64(ptr, 55, 1); =20 /* Trap if accessing an invalid page. */ tag_mem =3D allocation_tag_mem(env, mmu_idx, ptr, MMU_DATA_LOAD, @@ -472,6 +479,34 @@ uint64_t HELPER(ldgm)(CPUARMState *env, uint64_t ptr) =20 /* The tag is squashed to zero if the page does not support tags. */ if (!tag_mem) { + /* Load canonical value if mtx is set (untagged memory region) */ + if (canonical_tagging_enabled(env, bit55)) { + switch (gm_bs) { + case 3: + /* 32 bytes -> 2 tags -> 8 result bits */ + ret =3D -(uint8_t)bit55; + break; + case 4: + /* 64 bytes -> 4 tags -> 16 result bits */ + ret =3D -(uint16_t)bit55; + break; + case 5: + /* 128 bytes -> 8 tags -> 32 result bits */ + ret =3D -(uint32_t)bit55; + break; + case 6: + /* 256 bytes -> 16 tags -> 64 result bits */ + return -(uint64_t)bit55; + default: + /* + * CPU configured with unsupported/invalid gm blocksize. + * This is detected early in arm_cpu_realizefn. + */ + g_assert_not_reached(); + } + shift =3D extract64(ptr, LOG2_TAG_GRANULE, 4) * 4; + return ret << shift; + } return 0; } =20 --=20 2.52.0