Re: [PATCH v2 04/11] RISC-V: KVM: Modify SBI extension handler to return SBI error code

From: Andrew Jones
Date: Thu Jan 12 2023 - 06:14:45 EST

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On Thu, Dec 15, 2022 at 09:00:39AM -0800, Atish Patra wrote:
> Currently, the SBI extension handle is expected to return Linux error code.

handler

> The top SBI layer converts the Linux error code to SBI specific error code
> that can be returned to guest invoking the SBI calls. This model works
> as long as SBI error codes have 1-to-1 mappings between them.

as long as SBI and Linux error codes have 1-to-1...

> However, that may not be true always. This patch attempts to disassociate
> both these error codes by allowing the SBI extension implementation to
> return SBI specific error codes as well.
>
> The extension will continue to return the Linux error specific code which
> will indicate any problem *with* the extension emulation while the
> SBI specific error will indicate the problem *of* the emulation.
>
> Suggested-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> Signed-off-by: Atish Patra <atishp@xxxxxxxxxxxx>
> ---
> arch/riscv/include/asm/kvm_vcpu_sbi.h | 10 ++++--
> arch/riscv/kvm/vcpu_sbi.c | 45 ++++++++-------------------
> arch/riscv/kvm/vcpu_sbi_base.c | 38 +++++++++++-----------
> arch/riscv/kvm/vcpu_sbi_hsm.c | 22 +++++++------
> arch/riscv/kvm/vcpu_sbi_replace.c | 44 +++++++++++++-------------
> 5 files changed, 74 insertions(+), 85 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> index 61dac1b..fee9253 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> @@ -18,6 +18,12 @@ struct kvm_vcpu_sbi_context {
> int return_handled;
> };
>
> +struct kvm_vcpu_sbi_ext_data {
> + unsigned long out_val;
> + unsigned long err_val;
> + bool uexit;
> +};
> +
> struct kvm_vcpu_sbi_extension {
> unsigned long extid_start;
> unsigned long extid_end;
> @@ -27,8 +33,8 @@ struct kvm_vcpu_sbi_extension {
> * specific error codes.
> */
> int (*handler)(struct kvm_vcpu *vcpu, struct kvm_run *run,
> - unsigned long *out_val, struct kvm_cpu_trap *utrap,
> - bool *exit);
> + struct kvm_vcpu_sbi_ext_data *edata,
> + struct kvm_cpu_trap *utrap);
>
> /* Extension specific probe function */
> unsigned long (*probe)(struct kvm_vcpu *vcpu, unsigned long extid);
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> index f96991d..50c5472 100644
> --- a/arch/riscv/kvm/vcpu_sbi.c
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -12,26 +12,6 @@
> #include <asm/sbi.h>
> #include <asm/kvm_vcpu_sbi.h>
>
> -static int kvm_linux_err_map_sbi(int err)
> -{
> - switch (err) {
> - case 0:
> - return SBI_SUCCESS;
> - case -EPERM:
> - return SBI_ERR_DENIED;
> - case -EINVAL:
> - return SBI_ERR_INVALID_PARAM;
> - case -EFAULT:
> - return SBI_ERR_INVALID_ADDRESS;
> - case -EOPNOTSUPP:
> - return SBI_ERR_NOT_SUPPORTED;
> - case -EALREADY:
> - return SBI_ERR_ALREADY_AVAILABLE;
> - default:
> - return SBI_ERR_FAILURE;
> - };
> -}
> -
> #ifndef CONFIG_RISCV_SBI_V01
> static const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_v01 = {
> .extid_start = -1UL,
> @@ -125,11 +105,10 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
> {
> int ret = 1;
> bool next_sepc = true;
> - bool userspace_exit = false;
> struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> const struct kvm_vcpu_sbi_extension *sbi_ext;
> struct kvm_cpu_trap utrap = { 0 };
> - unsigned long out_val = 0;
> + struct kvm_vcpu_sbi_ext_data edata_out = { 0 };
> bool ext_is_v01 = false;
>
> sbi_ext = kvm_vcpu_sbi_find_ext(cp->a7);
> @@ -139,7 +118,7 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
> cp->a7 <= SBI_EXT_0_1_SHUTDOWN)
> ext_is_v01 = true;
> #endif
> - ret = sbi_ext->handler(vcpu, run, &out_val, &utrap, &userspace_exit);
> + ret = sbi_ext->handler(vcpu, run, &edata_out, &utrap);
> } else {
> /* Return error for unsupported SBI calls */
> cp->a0 = SBI_ERR_NOT_SUPPORTED;
> @@ -156,25 +135,27 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
> goto ecall_done;
> }
>
> + /* The SBI extension returns Linux error code. Exits the ioctl loop

Need opening /* wing

And for wording, maybe

When the SBI extension returns a Linux error code, it exist the ioctl
loop and forwards the error to userspace.

> + * and forwards the error to the userspace.
> + */
> + if (ret < 0) {
> + next_sepc = false;
> + goto ecall_done;
> + }

Shouldn't this ret < 0 check go above the "Handle special error cases..."
block?

> +
> /* Exit ioctl loop or Propagate the error code the guest */
> - if (userspace_exit) {
> + if (edata_out.uexit) {
> next_sepc = false;
> ret = 0;
> } else {
> - /**
> - * SBI extension handler always returns an Linux error code. Convert
> - * it to the SBI specific error code that can be propagated the SBI
> - * caller.
> - */
> - ret = kvm_linux_err_map_sbi(ret);
> - cp->a0 = ret;
> + cp->a0 = edata_out.err_val;
> ret = 1;
> }
> ecall_done:
> if (next_sepc)
> cp->sepc += 4;
> if (!ext_is_v01)
> - cp->a1 = out_val;
> + cp->a1 = edata_out.out_val;
>
> return ret;
> }
> diff --git a/arch/riscv/kvm/vcpu_sbi_base.c b/arch/riscv/kvm/vcpu_sbi_base.c
> index 89e2415..487828d 100644
> --- a/arch/riscv/kvm/vcpu_sbi_base.c
> +++ b/arch/riscv/kvm/vcpu_sbi_base.c
> @@ -14,24 +14,23 @@
> #include <asm/kvm_vcpu_sbi.h>
>
> static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> - unsigned long *out_val,
> - struct kvm_cpu_trap *trap, bool *exit)
> + struct kvm_vcpu_sbi_ext_data *edata,
> + struct kvm_cpu_trap *trap)
> {
> - int ret = 0;
> struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> const struct kvm_vcpu_sbi_extension *sbi_ext;
>
> switch (cp->a6) {
> case SBI_EXT_BASE_GET_SPEC_VERSION:
> - *out_val = (KVM_SBI_VERSION_MAJOR <<
> + edata->out_val = (KVM_SBI_VERSION_MAJOR <<
> SBI_SPEC_VERSION_MAJOR_SHIFT) |
> KVM_SBI_VERSION_MINOR;
> break;
> case SBI_EXT_BASE_GET_IMP_ID:
> - *out_val = KVM_SBI_IMPID;
> + edata->out_val = KVM_SBI_IMPID;
> break;
> case SBI_EXT_BASE_GET_IMP_VERSION:
> - *out_val = LINUX_VERSION_CODE;
> + edata->out_val = LINUX_VERSION_CODE;
> break;
> case SBI_EXT_BASE_PROBE_EXT:
> if ((cp->a0 >= SBI_EXT_EXPERIMENTAL_START &&
> @@ -43,33 +42,33 @@ static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> * forward it to the userspace
> */
> kvm_riscv_vcpu_sbi_forward(vcpu, run);
> - *exit = true;
> + edata->uexit = true;
> } else {
> sbi_ext = kvm_vcpu_sbi_find_ext(cp->a0);
> if (sbi_ext) {
> if (sbi_ext->probe)
> - *out_val = sbi_ext->probe(vcpu, cp->a0);
> + edata->out_val = sbi_ext->probe(vcpu, cp->a0);
> else
> - *out_val = 1;
> + edata->out_val = 1;
> } else
> - *out_val = 0;
> + edata->out_val = 0;
> }
> break;
> case SBI_EXT_BASE_GET_MVENDORID:
> - *out_val = vcpu->arch.mvendorid;
> + edata->out_val = vcpu->arch.mvendorid;
> break;
> case SBI_EXT_BASE_GET_MARCHID:
> - *out_val = vcpu->arch.marchid;
> + edata->out_val = vcpu->arch.marchid;
> break;
> case SBI_EXT_BASE_GET_MIMPID:
> - *out_val = vcpu->arch.mimpid;
> + edata->out_val = vcpu->arch.mimpid;
> break;
> default:
> - ret = -EOPNOTSUPP;
> + edata->err_val = SBI_ERR_NOT_SUPPORTED;
> break;
> }
>
> - return ret;
> + return 0;
> }
>
> const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_base = {
> @@ -79,17 +78,16 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_base = {
> };
>
> static int kvm_sbi_ext_forward_handler(struct kvm_vcpu *vcpu,
> - struct kvm_run *run,
> - unsigned long *out_val,
> - struct kvm_cpu_trap *utrap,
> - bool *exit)
> + struct kvm_run *run,
> + struct kvm_vcpu_sbi_ext_data *edata,
> + struct kvm_cpu_trap *utrap)
> {
> /*
> * Both SBI experimental and vendor extensions are
> * unconditionally forwarded to userspace.
> */
> kvm_riscv_vcpu_sbi_forward(vcpu, run);
> - *exit = true;
> + edata->uexit = true;
> return 0;
> }
>
> diff --git a/arch/riscv/kvm/vcpu_sbi_hsm.c b/arch/riscv/kvm/vcpu_sbi_hsm.c
> index 0f8d9fe..4188f21 100644
> --- a/arch/riscv/kvm/vcpu_sbi_hsm.c
> +++ b/arch/riscv/kvm/vcpu_sbi_hsm.c
> @@ -21,9 +21,9 @@ static int kvm_sbi_hsm_vcpu_start(struct kvm_vcpu *vcpu)
>
> target_vcpu = kvm_get_vcpu_by_id(vcpu->kvm, target_vcpuid);
> if (!target_vcpu)
> - return -EINVAL;
> + return SBI_ERR_INVALID_PARAM;
> if (!target_vcpu->arch.power_off)
> - return -EALREADY;
> + return SBI_ERR_ALREADY_AVAILABLE;
>
> reset_cntx = &target_vcpu->arch.guest_reset_context;
> /* start address */
> @@ -42,7 +42,7 @@ static int kvm_sbi_hsm_vcpu_start(struct kvm_vcpu *vcpu)
> static int kvm_sbi_hsm_vcpu_stop(struct kvm_vcpu *vcpu)
> {
> if (vcpu->arch.power_off)
> - return -EPERM;
> + return SBI_ERR_FAILURE;

-EPERM shouldn't map to SBI_ERR_FAILURE, but this should be addressed in
the previous patch.

>
> kvm_riscv_vcpu_power_off(vcpu);
>
> @@ -57,7 +57,7 @@ static int kvm_sbi_hsm_vcpu_get_status(struct kvm_vcpu *vcpu)
>
> target_vcpu = kvm_get_vcpu_by_id(vcpu->kvm, target_vcpuid);
> if (!target_vcpu)
> - return -EINVAL;
> + return SBI_ERR_INVALID_PARAM;
> if (!target_vcpu->arch.power_off)
> return SBI_HSM_STATE_STARTED;
> else if (vcpu->stat.generic.blocking)
> @@ -66,10 +66,10 @@ static int kvm_sbi_hsm_vcpu_get_status(struct kvm_vcpu *vcpu)
> return SBI_HSM_STATE_STOPPED;
> }
>
> +

stray new blank line

> static int kvm_sbi_ext_hsm_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> - unsigned long *out_val,
> - struct kvm_cpu_trap *utrap,
> - bool *exit)
> + struct kvm_vcpu_sbi_ext_data *edata,
> + struct kvm_cpu_trap *utrap)
> {
> int ret = 0;
> struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> @@ -88,8 +88,8 @@ static int kvm_sbi_ext_hsm_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> case SBI_EXT_HSM_HART_STATUS:
> ret = kvm_sbi_hsm_vcpu_get_status(vcpu);
> if (ret >= 0) {
> - *out_val = ret;
> - ret = 0;
> + edata->out_val = ret;
> + edata->err_val = 0;

We want a 'return 0;' here. Otherwise below we write ret to err_val.

> }
> break;
> case SBI_EXT_HSM_HART_SUSPEND:
> @@ -108,7 +108,9 @@ static int kvm_sbi_ext_hsm_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> ret = -EOPNOTSUPP;

This ret = -EOPNOTSUPP in the context and two others above it need to be
converted to SBI errors.

> }
>
> - return ret;
> + edata->err_val = ret;
> +
> + return 0;
> }
>
> const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm = {
> diff --git a/arch/riscv/kvm/vcpu_sbi_replace.c b/arch/riscv/kvm/vcpu_sbi_replace.c
> index 03a0198..d029136 100644
> --- a/arch/riscv/kvm/vcpu_sbi_replace.c
> +++ b/arch/riscv/kvm/vcpu_sbi_replace.c
> @@ -14,15 +14,17 @@
> #include <asm/kvm_vcpu_sbi.h>
>
> static int kvm_sbi_ext_time_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> - unsigned long *out_val,
> - struct kvm_cpu_trap *utrap, bool *exit)
> + struct kvm_vcpu_sbi_ext_data *edata,
> + struct kvm_cpu_trap *utrap)
> {
> int ret = 0;

ret is only used at the bottom to return 0. We can drop the variable and
change it to an explicit zero.

> struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> u64 next_cycle;
>
> - if (cp->a6 != SBI_EXT_TIME_SET_TIMER)
> - return -EINVAL;
> + if (cp->a6 != SBI_EXT_TIME_SET_TIMER) {
> + edata->err_val = SBI_ERR_INVALID_PARAM;
> + return 0;
> + }
>
> #if __riscv_xlen == 32
> next_cycle = ((u64)cp->a1 << 32) | (u64)cp->a0;
> @@ -41,8 +43,8 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_time = {
> };
>
> static int kvm_sbi_ext_ipi_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> - unsigned long *out_val,
> - struct kvm_cpu_trap *utrap, bool *exit)
> + struct kvm_vcpu_sbi_ext_data *edata,
> + struct kvm_cpu_trap *utrap)
> {
> int ret = 0;
> unsigned long i;
> @@ -51,8 +53,10 @@ static int kvm_sbi_ext_ipi_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> unsigned long hmask = cp->a0;
> unsigned long hbase = cp->a1;
>
> - if (cp->a6 != SBI_EXT_IPI_SEND_IPI)
> - return -EINVAL;
> + if (cp->a6 != SBI_EXT_IPI_SEND_IPI) {
> + edata->err_val = SBI_ERR_INVALID_PARAM;
> + return 0;
> + }
>
> kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
> if (hbase != -1UL) {
> @@ -76,10 +80,9 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_ipi = {
> };
>
> static int kvm_sbi_ext_rfence_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> - unsigned long *out_val,
> - struct kvm_cpu_trap *utrap, bool *exit)
> + struct kvm_vcpu_sbi_ext_data *edata,
> + struct kvm_cpu_trap *utrap)
> {
> - int ret = 0;
> struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> unsigned long hmask = cp->a0;
> unsigned long hbase = cp->a1;
> @@ -116,10 +119,10 @@ static int kvm_sbi_ext_rfence_handler(struct kvm_vcpu *vcpu, struct kvm_run *run
> */
> break;
> default:
> - ret = -EOPNOTSUPP;
> + edata->err_val = SBI_ERR_NOT_SUPPORTED;
> }
>
> - return ret;
> + return 0;
> }
>
> const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_rfence = {
> @@ -130,14 +133,13 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_rfence = {
>
> static int kvm_sbi_ext_srst_handler(struct kvm_vcpu *vcpu,
> struct kvm_run *run,
> - unsigned long *out_val,
> - struct kvm_cpu_trap *utrap, bool *exit)
> + struct kvm_vcpu_sbi_ext_data *edata,
> + struct kvm_cpu_trap *utrap)
> {
> struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> unsigned long funcid = cp->a6;
> u32 reason = cp->a1;
> u32 type = cp->a0;
> - int ret = 0;
>
> switch (funcid) {
> case SBI_EXT_SRST_RESET:
> @@ -146,24 +148,24 @@ static int kvm_sbi_ext_srst_handler(struct kvm_vcpu *vcpu,
> kvm_riscv_vcpu_sbi_system_reset(vcpu, run,
> KVM_SYSTEM_EVENT_SHUTDOWN,
> reason);
> - *exit = true;
> + edata->uexit = true;
> break;
> case SBI_SRST_RESET_TYPE_COLD_REBOOT:
> case SBI_SRST_RESET_TYPE_WARM_REBOOT:
> kvm_riscv_vcpu_sbi_system_reset(vcpu, run,
> KVM_SYSTEM_EVENT_RESET,
> reason);
> - *exit = true;
> + edata->uexit = true;
> break;
> default:
> - ret = -EOPNOTSUPP;
> + edata->err_val = SBI_ERR_NOT_SUPPORTED;
> }
> break;
> default:
> - ret = -EOPNOTSUPP;
> + edata->err_val = SBI_ERR_NOT_SUPPORTED;
> }
>
> - return ret;
> + return 0;
> }
>
> const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_srst = {
> --
> 2.25.1
>

Thanks,
drew

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