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Mon, 10 Aug 2026 19:56:25 -0700 (PDT) From: Zephyr Li To: qemu-devel@nongnu.org Cc: qemu-riscv@nongnu.org, palmer@dabbelt.com, alistair.francis@wdc.com, liwei1518@gmail.com, daniel.barboza@oss.qualcomm.com, zhiwei_liu@linux.alibaba.com, chao.liu@processmission.com, Zephyr Li Subject: [PATCH v3] target/riscv: preserve vl on element-zero fault Date: Tue, 11 Aug 2026 10:55:15 +0800 Message-ID: <20260811025516.337888-1-fritchleybohrer@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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=lists1p.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:39::8; envelope-from=fritchleybohrer@gmail.com; helo=mail-pj2-x08.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: 1786417044348158500 Content-Type: text/plain; charset="utf-8" A unit-stride fault-only-first load must leave vl unchanged when element zero raises a synchronous exception. Keep the shortened value in a local bound until all loads complete, and only then update the architectural vl. Add a bare-metal RVV regression test which faults vle32ff.v on element zero and checks that vl remains unchanged in the trap handler. Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3544 Signed-off-by: Zephyr Li Reviewed-by: Max Chou --- Changes in v3: - Rebase onto current master. - Regenerate the patch to fix the malformed v2 submission. Changes in v2: - Fix commit message formatting. - Enable vector state in the bare-metal test. - Use an aligned unmapped address and compare against the vsetvli result. - Express the mstatus.VS setting as a field shift. target/riscv/tcg/vector_helper.c | 23 +++++---- tests/tcg/riscv64/Makefile.softmmu-target | 5 ++ tests/tcg/riscv64/test-vle32ff.S | 57 +++++++++++++++++++++++ 3 files changed, 76 insertions(+), 9 deletions(-) create mode 100644 tests/tcg/riscv64/test-vle32ff.S diff --git a/target/riscv/tcg/vector_helper.c b/target/riscv/tcg/vector_hel= per.c index e321ca2616..5a310822b7 100644 --- a/target/riscv/tcg/vector_helper.c +++ b/target/riscv/tcg/vector_helper.c @@ -686,7 +686,7 @@ vext_ldff(void *vd, void *v0, target_ulong base, CPURIS= CVState *env, uint32_t desc, vext_ldst_elem_fn_tlb *ldst_tlb, vext_ldst_elem_fn_host *ldst_host, uint32_t log2_esz, uintptr_t = ra) { - uint32_t i, k, vl =3D 0; + uint32_t i, k, vl =3D 0, load_vl; uint32_t nf =3D vext_nf(desc); uint32_t vm =3D vext_vm(desc); uint32_t max_elems =3D vext_max_elems(desc, log2_esz); @@ -752,22 +752,24 @@ vext_ldff(void *vd, void *v0, target_ulong base, CPUR= ISCVState *env, } } ProbeSuccess: - /* load bytes from guest memory */ - if (vl !=3D 0) { - env->vl =3D vl; - } + /* + * Keep a shortened vl local until all loads complete. In particular, + * an exception from element zero must leave the architectural vl alon= e. + */ + load_vl =3D vl ? vl : env->vl; =20 - if (env->vstart < env->vl) { + if (env->vstart < load_vl) { if (vm) { /* Load/store elements in the first page */ if (likely(elems)) { + elems =3D MIN(elems, load_vl - env->vstart); vext_page_ldst_us(env, vd, addr, elems, nf, max_elems, log2_esz, true, mmu_index, ldst_tlb, ldst_host, ra); } =20 /* Load/store elements in the second page */ - if (unlikely(env->vstart < env->vl)) { + if (unlikely(env->vstart < load_vl)) { /* Cross page element */ if (unlikely(page_split % msize)) { for (k =3D 0; k < nf; k++) { @@ -780,7 +782,7 @@ ProbeSuccess: =20 addr =3D base + ((env->vstart * nf) << log2_esz); /* Get number of elements of second page */ - elems =3D env->vl - env->vstart; + elems =3D load_vl - env->vstart; =20 /* Load/store elements in the second page */ vext_page_ldst_us(env, vd, addr, elems, nf, max_elems, @@ -788,7 +790,7 @@ ProbeSuccess: ldst_host, ra); } } else { - for (i =3D env->vstart; i < env->vl; i++) { + for (i =3D env->vstart; i < load_vl; i++) { k =3D 0; while (k < nf) { if (!vext_elem_mask(v0, i)) { @@ -806,6 +808,9 @@ ProbeSuccess: } } } + if (vl !=3D 0) { + env->vl =3D vl; + } env->vstart =3D 0; =20 vext_set_tail_elems_1s(env->vl, vd, desc, nf, esz, max_elems); diff --git a/tests/tcg/riscv64/Makefile.softmmu-target b/tests/tcg/riscv64/= Makefile.softmmu-target index 82be8a2c91..7ae225bd73 100644 --- a/tests/tcg/riscv64/Makefile.softmmu-target +++ b/tests/tcg/riscv64/Makefile.softmmu-target @@ -41,5 +41,10 @@ comma:=3D , run-test-crc32: test-crc32 $(call run-test, $<, $(QEMU) -cpu rv64$(comma)xlrbr=3Dtrue $(QEMU_OPTS)$<) =20 +EXTRA_RUNS +=3D run-test-vle32ff +run-test-vle32ff: test-vle32ff + $(call run-test, $<, $(QEMU) -cpu rv64$(comma)v=3Dtrue $(QEMU_OPTS)$<) +test-vle32ff: CFLAGS +=3D -march=3Drv64gcv + # We don't currently support the multiarch system tests undefine MULTIARCH_TESTS diff --git a/tests/tcg/riscv64/test-vle32ff.S b/tests/tcg/riscv64/test-vle3= 2ff.S new file mode 100644 index 0000000000..f510960c05 --- /dev/null +++ b/tests/tcg/riscv64/test-vle32ff.S @@ -0,0 +1,57 @@ +/* + * Verify that a fault-only-first load keeps vl unchanged when element zero + * raises a synchronous exception. + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + + .option norvc + + .text + .globl _start +_start: + lla t0, trap + csrw mtvec, t0 + + li t0, (1 << 9) /* Set mstatus.VS to Initial. */ + csrs mstatus, t0 + li t1, 4 + vsetvli t2, t1, e32, m1, ta, ma + li t0, 0x18000000 /* Unmapped gap in the virt memory map. */ + vle32ff.v v1, (t0) + + /* Element zero did not trap. */ + li a0, 1 + j _exit + +trap: + csrr t0, mcause + li t1, 5 /* Load access fault. */ + bne t0, t1, trap_fail + + csrr t0, vl + bne t0, t2, trap_fail + + li a0, 0 + j _exit + +trap_fail: + li a0, 1 + +_exit: + lla a1, semiargs + li t0, 0x20026 /* ADP_Stopped_ApplicationExit */ + sd t0, 0(a1) + sd a0, 8(a1) + li a0, 0x20 /* TARGET_SYS_EXIT_EXTENDED */ + + .balign 16 + slli zero, zero, 0x1f + ebreak + srai zero, zero, 0x7 + j . + + .data + .balign 8 +semiargs: + .space 16 --=20 2.43.0