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SubjectRe: [PATCH v3 06/14] RISC-V: KVM: Modify SBI extension handler to return SBI error code
On Sun, Jan 29, 2023 at 4:16 AM Anup Patel <anup@brainfault.org> wrote:
>
> On Fri, Jan 27, 2023 at 11:56 PM Atish Patra <atishp@rivosinc.com> wrote:
> >
> > Currently, the SBI extension handle is expected to return Linux error code.
> > 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.
> > 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@ventanamicro.com>
> > Signed-off-by: Atish Patra <atishp@rivosinc.com>
> > ---
> > arch/riscv/include/asm/kvm_vcpu_sbi.h | 10 ++++--
> > arch/riscv/kvm/vcpu_sbi.c | 46 ++++++++------------------
> > arch/riscv/kvm/vcpu_sbi_base.c | 38 ++++++++++------------
> > arch/riscv/kvm/vcpu_sbi_hsm.c | 29 +++++++++--------
> > arch/riscv/kvm/vcpu_sbi_replace.c | 47 ++++++++++++++-------------
> > arch/riscv/kvm/vcpu_sbi_v01.c | 11 +++----
> > 6 files changed, 84 insertions(+), 97 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> > index 45ba341..38407b3 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 {
>
> s/kvm_vcpu_sbi_ext_data/kvm_vcpu_sbi_return/
>
> > + unsigned long out_val;
> > + unsigned long err_val;
>
> Add "struct kvm_cpu_trap utrap" here.
>

Done.

> > + 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);
> > diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> > index f96991d..aa42da6 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 };
>
> Remove "struct kvm_cpu_trap utrap" from here since it can be
> part of "struct kvm_vcpu_sbi_return"
>

Done.

> > - 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);
> > @@ -139,13 +118,22 @@ 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;
> > goto ecall_done;
> > }
> >
> > + /*
> > + * When the SBI extension returns a Linux error code, it exits the ioctl
> > + * loop and forwards the error to userspace.
> > + */
> > + if (ret < 0) {
> > + next_sepc = false;
> > + goto ecall_done;
> > + }
> > +
> > /* Handle special error cases i.e trap, exit or userspace forward */
> > if (utrap.scause) {
> > /* No need to increment sepc or exit ioctl loop */
> > @@ -157,24 +145,18 @@ int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run)
> > }
> >
> > /* 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;
>
> Strange! This now updates the "a1" register when ret < 0 which it should not.
>
> Ideally, the "a1" register should be only updated when "ret == 1".
>

Ahh. Thanks for catching that. Fixed that.
Earlier, we were updating a1 register for the userspace exit scenario.
I have fixed that as well.

> >
> > return ret;
> > }
> > diff --git a/arch/riscv/kvm/vcpu_sbi_base.c b/arch/riscv/kvm/vcpu_sbi_base.c
> > index 846d518..84885e5 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);
> > + edata->out_val = sbi_ext->probe(vcpu);
> > 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 619ac0f..5fb526c 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 -EACCES;
> > + return SBI_ERR_FAILURE;
> >
> > 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)
> > @@ -67,9 +67,8 @@ static int kvm_sbi_hsm_vcpu_get_status(struct kvm_vcpu *vcpu)
> > }
> >
> > 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;
> > @@ -88,27 +87,29 @@ 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;
> > }
> > - break;
> > + return 0;
> > case SBI_EXT_HSM_HART_SUSPEND:
> > switch (cp->a0) {
> > case SBI_HSM_SUSPEND_RET_DEFAULT:
> > kvm_riscv_vcpu_wfi(vcpu);
> > break;
> > case SBI_HSM_SUSPEND_NON_RET_DEFAULT:
> > - ret = -EOPNOTSUPP;
> > + ret = SBI_ERR_NOT_SUPPORTED;
> > break;
> > default:
> > - ret = -EINVAL;
> > + ret = SBI_ERR_INVALID_PARAM;
> > }
> > break;
> > default:
> > - ret = -EOPNOTSUPP;
> > + ret = SBI_ERR_NOT_SUPPORTED;
> > }
> >
> > - 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..abeb55f 100644
> > --- a/arch/riscv/kvm/vcpu_sbi_replace.c
> > +++ b/arch/riscv/kvm/vcpu_sbi_replace.c
> > @@ -14,15 +14,16 @@
> > #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;
> > 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;
> > @@ -31,7 +32,7 @@ static int kvm_sbi_ext_time_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> > #endif
> > kvm_riscv_vcpu_timer_next_event(vcpu, next_cycle);
> >
> > - return ret;
> > + return 0;
> > }
> >
> > const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_time = {
> > @@ -41,8 +42,8 @@ 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 +52,10 @@ 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 +79,9 @@ 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 +118,10 @@ 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 +132,13 @@ 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 +147,24 @@ 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 = {
> > diff --git a/arch/riscv/kvm/vcpu_sbi_v01.c b/arch/riscv/kvm/vcpu_sbi_v01.c
> > index 489f225..c0ccc58 100644
> > --- a/arch/riscv/kvm/vcpu_sbi_v01.c
> > +++ b/arch/riscv/kvm/vcpu_sbi_v01.c
> > @@ -14,9 +14,8 @@
> > #include <asm/kvm_vcpu_sbi.h>
> >
> > static int kvm_sbi_ext_v01_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)
> > {
> > ulong hmask;
> > int i, ret = 0;
> > @@ -33,7 +32,7 @@ static int kvm_sbi_ext_v01_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> > * handled in kernel so we forward these to user-space
> > */
> > kvm_riscv_vcpu_sbi_forward(vcpu, run);
> > - *exit = true;
> > + edata->uexit = true;
> > break;
> > case SBI_EXT_0_1_SET_TIMER:
> > #if __riscv_xlen == 32
> > @@ -65,7 +64,7 @@ static int kvm_sbi_ext_v01_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> > case SBI_EXT_0_1_SHUTDOWN:
> > kvm_riscv_vcpu_sbi_system_reset(vcpu, run,
> > KVM_SYSTEM_EVENT_SHUTDOWN, 0);
> > - *exit = true;
> > + edata->uexit = true;
> > break;
> > case SBI_EXT_0_1_REMOTE_FENCE_I:
> > case SBI_EXT_0_1_REMOTE_SFENCE_VMA:
> > @@ -103,7 +102,7 @@ static int kvm_sbi_ext_v01_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> > }
> > break;
> > default:
> > - ret = -EINVAL;
> > + edata->err_val = SBI_ERR_NOT_SUPPORTED;
> > break;
> > }
> >
> > --
> > 2.25.1
> >
>
> Regards,
> Anup



--
Regards,
Atish

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