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Tue, 06 Jan 2026 00:05:27 -0800 (PST) From: Jay Chang To: qemu-devel@nongnu.org, qemu-riscv@nongnu.org Cc: Palmer Dabbelt , Alistair Francis , Weiwei Li , Daniel Henrique Barboza , Liu Zhiwei , Jay Chang , Frank Chang Subject: [PATCH] hw/riscv: riscv-iommu: Re-process command queue after clearing CMD_ILL Date: Tue, 6 Jan 2026 16:05:20 +0800 Message-ID: <20260106080520.28711-1-jay.chang@sifive.com> X-Mailer: git-send-email 2.48.1 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=lists.gnu.org; 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::62c; envelope-from=jay.chang@sifive.com; helo=mail-pl1-x62c.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, 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: 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 @sifive.com) X-ZM-MESSAGEID: 1767686809947158500 Content-Type: text/plain; charset="utf-8" When software clears CMD_ILL or CQMF error bits by writing 1 to CQCSR, the IOMMU should re-check the command queue and continue processing pending commands if head !=3D tail. Per RISC-V IOMMU specification, the software error recovery sequence: 1. Read the head pointer 2. Software has two options: - Option 1: Set tail =3D head to re-start from an empty queue - Option 2: Overwrite the illegal command with a valid one 3. Re-enable the command queue by writing 1 to cqcsr.cmd_ill "At this point, IOMMU will start working on the first command in the queue." Signed-off-by: Jay Chang Reviewed-by: Frank Chang Reviewed-by: Daniel Henrique Barboza --- hw/riscv/riscv-iommu.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/hw/riscv/riscv-iommu.c b/hw/riscv/riscv-iommu.c index b46b337375..e89a262a63 100644 --- a/hw/riscv/riscv-iommu.c +++ b/hw/riscv/riscv-iommu.c @@ -1992,6 +1992,16 @@ static void riscv_iommu_process_cq_control(RISCVIOMM= UState *s) } =20 riscv_iommu_reg_mod32(s, RISCV_IOMMU_REG_CQCSR, ctrl_set, ctrl_clr); + + /* + * After clearing error bits (CMD_ILL, CQMF), if queue is still active, + * re-process pending command. + */ + ctrl_set =3D riscv_iommu_reg_get32(s, RISCV_IOMMU_REG_CQCSR); + if ((ctrl_set & RISCV_IOMMU_CQCSR_CQON) && + !(ctrl_set & (RISCV_IOMMU_CQCSR_CMD_ILL | RISCV_IOMMU_CQCSR_CQMF))= ) { + riscv_iommu_process_cq_tail(s); + } } =20 static void riscv_iommu_process_fq_control(RISCVIOMMUState *s) --=20 2.48.1