[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_E0qBLbLKhfv=+jb0s...@mail.gmail.com/ Fixes: 4db19d5b21 ("target/riscv/kvm: add missing KVM CSRs") Reported-by: Andrea Bolognani <abolo...@redhat.com> Signed-off-by: Daniel Henrique Barboza <dbarb...@ventanamicro.com> --- target/riscv/kvm/kvm-cpu.c | 63 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 60 insertions(+), 3 deletions(-) diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c index 99a4f01b15..ec74520872 100644 --- a/target/riscv/kvm/kvm-cpu.c +++ b/target/riscv/kvm/kvm-cpu.c @@ -638,6 +638,10 @@ static int kvm_riscv_get_regs_csr(CPUState *cs) for (i = 0; i < ARRAY_SIZE(kvm_csr_cfgs); i++) { KVMCPUConfig *csr_cfg = &kvm_csr_cfgs[i]; + if (!csr_cfg->supported) { + continue; + } + ret = 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 = 0; i < ARRAY_SIZE(kvm_csr_cfgs); i++) { KVMCPUConfig *csr_cfg = &kvm_csr_cfgs[i]; + if (!csr_cfg->supported) { + continue; + } + if (csr_cfg->prop_size == sizeof(uint32_t)) { reg = kvm_cpu_csr_get_u32(cpu, csr_cfg); } else { @@ -1088,6 +1096,32 @@ static void kvm_riscv_read_multiext_legacy(RISCVCPU *cpu, } } +static void kvm_riscv_read_csr_cfg_legacy(KVMScratchCPU *kvmcpu) +{ + uint64_t val; + int i, ret; + + for (i = 0; i < ARRAY_SIZE(kvm_csr_cfgs); i++) { + KVMCPUConfig *csr_cfg = &kvm_csr_cfgs[i]; + struct kvm_one_reg reg; + + reg.id = csr_cfg->kvm_reg_id; + reg.addr = (uint64_t)&val; + ret = ioctl(kvmcpu->cpufd, KVM_GET_ONE_REG, ®); + if (ret != 0) { + if (errno == EINVAL) { + csr_cfg->supported = false; + } else { + error_report("Unable to read KVM CSR %s: %s", + csr_cfg->name, strerror(errno)); + exit(EXIT_FAILURE); + } + } else { + csr_cfg->supported = true; + } + } +} + static int uint64_cmp(const void *a, const void *b) { uint64_t val1 = *(const uint64_t *)a; @@ -1144,7 +1178,27 @@ static void kvm_riscv_read_vlenb(RISCVCPU *cpu, KVMScratchCPU *kvmcpu, } } -static void kvm_riscv_init_multiext_cfg(RISCVCPU *cpu, KVMScratchCPU *kvmcpu) +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 = 0; i < ARRAY_SIZE(kvm_csr_cfgs); i++) { + KVMCPUConfig *csr_cfg = &kvm_csr_cfgs[i]; + + reg_id = csr_cfg->kvm_reg_id; + reg_search = bsearch(®_id, reglist->reg, reglist->n, + sizeof(uint64_t), uint64_cmp); + if (!reg_search) { + continue; + } + + csr_cfg->supported = true; + } +} + +static void kvm_riscv_init_multiext_csr_cfg(RISCVCPU *cpu, + KVMScratchCPU *kvmcpu) { KVMCPUConfig *multi_ext_cfg; struct kvm_one_reg reg; @@ -1161,7 +1215,9 @@ static void kvm_riscv_init_multiext_cfg(RISCVCPU *cpu, KVMScratchCPU *kvmcpu) * (EINVAL). Use read_legacy() in this case. */ if (errno == 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 != E2BIG) { /* * E2BIG is an expected error message for the API since we @@ -1224,6 +1280,7 @@ static void kvm_riscv_init_multiext_cfg(RISCVCPU *cpu, KVMScratchCPU *kvmcpu) } kvm_riscv_check_sbi_dbcn_support(cpu, reglist); + kvm_riscv_read_csr_cfg(reglist); } static void riscv_init_kvm_registers(Object *cpu_obj) @@ -1237,7 +1294,7 @@ static void riscv_init_kvm_registers(Object *cpu_obj) 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_multiext_csr_cfg(cpu, &kvmcpu); kvm_riscv_destroy_scratch_vcpu(&kvmcpu); } -- 2.49.0
