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envelope-from=chao.liu@processmission.com; helo=TYPPR03CU001.outbound.protection.outlook.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_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-riscv@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-riscv-bounces+qemu-riscv=archiver.kernel.org@nongnu.org Sender: qemu-riscv-bounces+qemu-riscv=archiver.kernel.org@nongnu.org On Mon, Aug 17, 2026 at 06:06:37PM +0800, Vladimir Isaev wrote: > According to spec: > > Writing misa may increase IALIGN, e.g., by disabling the "C" extension. > > If an instruction that would write misa increases IALIGN, and the > > subsequent instruction’s address is not IALIGN-bit aligned, the > > write to misa is suppressed, leaving misa unchanged. > > So attempt to disable C extension if next instruction is not aligned should not > change the misa. > > Reviewed-by: Alistair Francis > Signed-off-by: Vladimir Isaev Reviewed-by: Chao Liu Thanks, Chao > --- > target/riscv/tcg/csr.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/target/riscv/tcg/csr.c b/target/riscv/tcg/csr.c > index 36f2004bc5..dbfb3381ef 100644 > --- a/target/riscv/tcg/csr.c > +++ b/target/riscv/tcg/csr.c > @@ -2182,9 +2182,13 @@ static RISCVException write_misa(CPURISCVState *env, int csrno, > /* Mask extensions that are not supported by this hart */ > val &= env->misa_ext_mask; > > - /* Suppress 'C' if next instruction is not aligned. */ > - if ((val & RVC) && (get_next_pc(env, ra) & 3) != 0) { > - val &= ~RVC; > + /* drop write if RVC is cleared and next instruction is not aligned */ > + if ((env->misa_ext & RVC) && !(val & RVC) && > + (get_next_pc(env, ra) & 3) != 0) { > + qemu_log_mask(LOG_GUEST_ERROR, "Unable to write MISA ext value " > + "0x%x, MISA.C disable failed\n", env->misa_ext); > + > + return RISCV_EXCP_NONE; > } > > /* Disable RVG if any of its dependencies are disabled */ > -- > 2.55.0 >