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Mon, 09 Mar 2026 15:00:49 -0700 (PDT) Received: from [172.26.74.149] ([185.213.193.97]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7990a54ba7csm5218437b3.19.2026.03.09.15.00.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); 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: 7bit 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; 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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, uint64_t xt) /* Load if page supports tags. */ if (mem) { rtag = load_tag1(ptr, mem); + } else { + uint64_t bit55 = extract64(ptr, 55, 1); + if (canonical_tagging_enabled(env, bit55)) { + rtag = 0xF * bit55; + } } 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; ptr = QEMU_ALIGN_DOWN(ptr, gm_bs_bytes); + bit55 = extract64(ptr, 55, 1); /* Trap if accessing an invalid page. */ tag_mem = allocation_tag_mem(env, mmu_idx, ptr, MMU_DATA_LOAD, @@ -472,6 +479,34 @@ uint64_t HELPER(ldgm)(CPUARMState *env, uint64_t ptr) /* 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 = -(uint8_t)bit55; + break; + case 4: + /* 64 bytes -> 4 tags -> 16 result bits */ + ret = -(uint16_t)bit55; + break; + case 5: + /* 128 bytes -> 8 tags -> 32 result bits */ + ret = -(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 = extract64(ptr, LOG2_TAG_GRANULE, 4) * 4; + return ret << shift; + } return 0; } -- 2.52.0