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Fri, 25 Apr 2025 04:37:37 -0700 (PDT) From: Daniel Henrique Barboza To: qemu-devel@nongnu.org Cc: qemu-riscv@nongnu.org, alistair.francis@wdc.com, liwei1518@gmail.com, zhiwei_liu@linux.alibaba.com, palmer@rivosinc.com, ajones@ventanamicro.com, Daniel Henrique Barboza , Andrea Bolognani Subject: [PATCH v2 6/9] target/riscv/kvm: do not read unavailable CSRs Date: Fri, 25 Apr 2025 08:37:02 -0300 Message-ID: <20250425113705.2741457-7-dbarboza@ventanamicro.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250425113705.2741457-1-dbarboza@ventanamicro.com> References: <20250425113705.2741457-1-dbarboza@ventanamicro.com> 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 client-ip=2607:f8b0:4864:20::633; envelope-from=dbarboza@ventanamicro.com; helo=mail-pl1-x633.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=unavailable 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 @ventanamicro.com) X-ZM-MESSAGEID: 1745581128731019100 Content-Type: text/plain; charset="utf-8" [1] reports that commit 4db19d5b21 broke a KVM guest running kernel 6.6. This happens because the kernel does not know 'senvcfg', making it unable to boot because QEMU is reading/wriiting it without any checks. After converting the CSRs to do "automated" get/put reg procedures in the previous patch we can now scan for availability. Two functions are created: - kvm_riscv_read_csr_cfg_legacy() will check if the CSR exists by brute forcing KVM_GET_ONE_REG in each one of them, interpreting an EINVAL return as indication that the CSR isn't available. This will be use in absence of KVM_GET_REG_LIST; - kvm_riscv_read_csr_cfg() will use the existing result of get_reg_list to check if the CSRs ids are present. kvm_riscv_init_multiext_cfg() is now kvm_riscv_init_multiext_csr_cfg() to reflect that the function is also dealing with CSRs. [1] https://lore.kernel.org/qemu-riscv/CABJz62OfUDHYkQ0T3rGHStQprf1c7_E0qBL= bLKhfv=3D+jb0SYAw@mail.gmail.com/ Fixes: 4db19d5b21 ("target/riscv/kvm: add missing KVM CSRs") Reported-by: Andrea Bolognani Signed-off-by: Daniel Henrique Barboza Reviewed-by: Andrew Jones --- target/riscv/kvm/kvm-cpu.c | 62 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 59 insertions(+), 3 deletions(-) diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c index 7cbe566e5f..f341085ba1 100644 --- a/target/riscv/kvm/kvm-cpu.c +++ b/target/riscv/kvm/kvm-cpu.c @@ -636,6 +636,10 @@ static int kvm_riscv_get_regs_csr(CPUState *cs) for (i =3D 0; i < ARRAY_SIZE(kvm_csr_cfgs); i++) { KVMCPUConfig *csr_cfg =3D &kvm_csr_cfgs[i]; =20 + if (!csr_cfg->supported) { + continue; + } + ret =3D kvm_get_one_reg(cs, csr_cfg->kvm_reg_id, ®); if (ret) { return ret; @@ -662,6 +666,10 @@ static int kvm_riscv_put_regs_csr(CPUState *cs) for (i =3D 0; i < ARRAY_SIZE(kvm_csr_cfgs); i++) { KVMCPUConfig *csr_cfg =3D &kvm_csr_cfgs[i]; =20 + if (!csr_cfg->supported) { + continue; + } + if (KVM_REG_SIZE(csr_cfg->kvm_reg_id) =3D=3D sizeof(uint32_t)) { reg =3D kvm_cpu_csr_get_u32(cpu, csr_cfg); } else if (KVM_REG_SIZE(csr_cfg->kvm_reg_id) =3D=3D sizeof(uint64_= t)) { @@ -1090,6 +1098,32 @@ static void kvm_riscv_read_multiext_legacy(RISCVCPU = *cpu, } } =20 +static void kvm_riscv_read_csr_cfg_legacy(KVMScratchCPU *kvmcpu) +{ + uint64_t val; + int i, ret; + + for (i =3D 0; i < ARRAY_SIZE(kvm_csr_cfgs); i++) { + KVMCPUConfig *csr_cfg =3D &kvm_csr_cfgs[i]; + struct kvm_one_reg reg; + + reg.id =3D csr_cfg->kvm_reg_id; + reg.addr =3D (uint64_t)&val; + ret =3D ioctl(kvmcpu->cpufd, KVM_GET_ONE_REG, ®); + if (ret !=3D 0) { + if (errno =3D=3D EINVAL) { + csr_cfg->supported =3D false; + } else { + error_report("Unable to read KVM CSR %s: %s", + csr_cfg->name, strerror(errno)); + exit(EXIT_FAILURE); + } + } else { + csr_cfg->supported =3D true; + } + } +} + static int uint64_cmp(const void *a, const void *b) { uint64_t val1 =3D *(const uint64_t *)a; @@ -1146,7 +1180,26 @@ static void kvm_riscv_read_vlenb(RISCVCPU *cpu, KVMS= cratchCPU *kvmcpu, } } =20 -static void kvm_riscv_init_multiext_cfg(RISCVCPU *cpu, KVMScratchCPU *kvmc= pu) +static void kvm_riscv_read_csr_cfg(struct kvm_reg_list *reglist) +{ + struct kvm_reg_list *reg_search; + uint64_t reg_id; + + for (int i =3D 0; i < ARRAY_SIZE(kvm_csr_cfgs); i++) { + KVMCPUConfig *csr_cfg =3D &kvm_csr_cfgs[i]; + + reg_id =3D csr_cfg->kvm_reg_id; + reg_search =3D bsearch(®_id, reglist->reg, reglist->n, + sizeof(uint64_t), uint64_cmp); + if (!reg_search) { + continue; + } + + csr_cfg->supported =3D true; + } +} + +static void kvm_riscv_init_cfg(RISCVCPU *cpu, KVMScratchCPU *kvmcpu) { g_autofree struct kvm_reg_list *reglist =3D NULL; KVMCPUConfig *multi_ext_cfg; @@ -1163,7 +1216,9 @@ static void kvm_riscv_init_multiext_cfg(RISCVCPU *cpu= , KVMScratchCPU *kvmcpu) * (EINVAL). Use read_legacy() in this case. */ if (errno =3D=3D EINVAL) { - return kvm_riscv_read_multiext_legacy(cpu, kvmcpu); + kvm_riscv_read_multiext_legacy(cpu, kvmcpu); + kvm_riscv_read_csr_cfg_legacy(kvmcpu); + return; } else if (errno !=3D E2BIG) { /* * E2BIG is an expected error message for the API since we @@ -1226,6 +1281,7 @@ static void kvm_riscv_init_multiext_cfg(RISCVCPU *cpu= , KVMScratchCPU *kvmcpu) } =20 kvm_riscv_check_sbi_dbcn_support(cpu, reglist); + kvm_riscv_read_csr_cfg(reglist); } =20 static void riscv_init_kvm_registers(Object *cpu_obj) @@ -1239,7 +1295,7 @@ static void riscv_init_kvm_registers(Object *cpu_obj) =20 kvm_riscv_init_machine_ids(cpu, &kvmcpu); kvm_riscv_init_misa_ext_mask(cpu, &kvmcpu); - kvm_riscv_init_multiext_cfg(cpu, &kvmcpu); + kvm_riscv_init_cfg(cpu, &kvmcpu); =20 kvm_riscv_destroy_scratch_vcpu(&kvmcpu); } --=20 2.49.0