Re: [Qemu-devel] [PATCH v2 14/17] target-arm: A64: Emulate the HVC insn

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Wed, Jun 11, 2014 at 03:14:34PM -0500, Greg Bellows wrote:
> On 9 June 2014 10:04, Edgar E. Iglesias <edgar.iglesias@gmail.com> wrote:
> 
> > From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
> >
> > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> > ---
> >  target-arm/cpu.h           |  1 +
> >  target-arm/helper-a64.c    |  1 +
> >  target-arm/helper.c        | 28 +++++++++++++++++++++++++++-
> >  target-arm/helper.h        |  1 +
> >  target-arm/internals.h     |  6 ++++++
> >  target-arm/op_helper.c     | 21 +++++++++++++++++++++
> >  target-arm/translate-a64.c | 21 ++++++++++++++++-----
> >  7 files changed, 73 insertions(+), 6 deletions(-)
> >
> > diff --git a/target-arm/cpu.h b/target-arm/cpu.h
> > index 6aed57c..679f85f 100644
> > --- a/target-arm/cpu.h
> > +++ b/target-arm/cpu.h
> > @@ -51,6 +51,7 @@
> >  #define EXCP_EXCEPTION_EXIT  8   /* Return from v7M exception.  */
> >  #define EXCP_KERNEL_TRAP     9   /* Jumped to kernel code page.  */
> >  #define EXCP_STREX          10
> > +#define EXCP_HVC            11   /* HyperVisor Call */
> >
> >  #define ARMV7M_EXCP_RESET   1
> >  #define ARMV7M_EXCP_NMI     2
> > diff --git a/target-arm/helper-a64.c b/target-arm/helper-a64.c
> > index c91005f..974fa66 100644
> > --- a/target-arm/helper-a64.c
> > +++ b/target-arm/helper-a64.c
> > @@ -475,6 +475,7 @@ void aarch64_cpu_do_interrupt(CPUState *cs)
> >      case EXCP_BKPT:
> >      case EXCP_UDEF:
> >      case EXCP_SWI:
> > +    case EXCP_HVC:
> >          env->cp15.esr_el[new_el] = env->exception.syndrome;
> >          break;
> >      case EXCP_IRQ:
> > diff --git a/target-arm/helper.c b/target-arm/helper.c
> > index 86e098f..89ccfa8 100644
> > --- a/target-arm/helper.c
> > +++ b/target-arm/helper.c
> > @@ -3282,7 +3282,33 @@ void switch_mode(CPUARMState *env, int mode)
> >   */
> >  unsigned int arm_excp_target_el(CPUState *cs, unsigned int excp_idx)
> >  {
> > -    return 1;
> > +    CPUARMState *env = cs->env_ptr;
> > +    unsigned int cur_el = arm_current_pl(env);
> > +    unsigned int target_el = 1;
> > +    bool route_to_el2 = false;
> > +    /* FIXME: Use actual secure state.  */
> > +    bool secure = false;
> > +
> > +    if (!env->aarch64) {
> > +        /* TODO: Add EL2 and 3 exception handling for AArch32.  */
> > +        return 1;
> > +    }
> > +
> > +    if (!secure
> > +        && arm_feature(env, ARM_FEATURE_EL2)
> > +        && cur_el < 2
> > +        && (env->cp15.hcr_el2 & HCR_TGE)) {
> > +        route_to_el2 = true;
> > +    }
> > +
> > +    target_el = MAX(cur_el, route_to_el2 ? 2 : 1);
> > +
> > +    switch (excp_idx) {
> > +    case EXCP_HVC:
> > +        target_el = MAX(target_el, 2);
> > +        break;
> > +    }
> > +    return target_el;
> >  }
> >
> >  static void v7m_push(CPUARMState *env, uint32_t val)
> > diff --git a/target-arm/helper.h b/target-arm/helper.h
> > index b63fd0f..fb711be 100644
> > --- a/target-arm/helper.h
> > +++ b/target-arm/helper.h
> > @@ -50,6 +50,7 @@ DEF_HELPER_2(exception_internal, void, env, i32)
> >  DEF_HELPER_3(exception_with_syndrome, void, env, i32, i32)
> >  DEF_HELPER_1(wfi, void, env)
> >  DEF_HELPER_1(wfe, void, env)
> > +DEF_HELPER_2(hvc, void, env, i32)
> >
> >  DEF_HELPER_3(cpsr_write, void, env, i32, i32)
> >  DEF_HELPER_1(cpsr_read, i32, env)
> > diff --git a/target-arm/internals.h b/target-arm/internals.h
> > index 707643e..2da7a1b 100644
> > --- a/target-arm/internals.h
> > +++ b/target-arm/internals.h
> > @@ -53,6 +53,7 @@ static const char * const excnames[] = {
> >      [EXCP_EXCEPTION_EXIT] = "QEMU v7M exception exit",
> >      [EXCP_KERNEL_TRAP] = "QEMU intercept of kernel commpage",
> >      [EXCP_STREX] = "QEMU intercept of STREX",
> > +    [EXCP_HVC] = "Hypervisor Call",
> >  };
> >
> >  static inline void arm_log_exception(int idx)
> > @@ -204,6 +205,11 @@ static inline uint32_t syn_aa64_svc(uint16_t imm16)
> >      return (EC_AA64_SVC << ARM_EL_EC_SHIFT) | ARM_EL_IL | imm16;
> >  }
> >
> > +static inline uint32_t syn_aa64_hvc(uint16_t imm16)
> > +{
> > +    return (EC_AA64_HVC << ARM_EL_EC_SHIFT) | ARM_EL_IL | imm16;
> > +}
> > +
> >
> 
> See comment on 13/17 with regards to uint16_t.
> 
> 
> >  static inline uint32_t syn_aa32_svc(uint16_t imm16, bool is_thumb)
> >  {
> >      return (EC_AA32_SVC << ARM_EL_EC_SHIFT) | imm16
> > diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
> > index 25ad902..e51cbd6 100644
> > --- a/target-arm/op_helper.c
> > +++ b/target-arm/op_helper.c
> > @@ -369,6 +369,27 @@ void HELPER(msr_i_pstate)(CPUARMState *env, uint32_t
> > op, uint32_t imm)
> >      }
> >  }
> >
> > +void HELPER(hvc)(CPUARMState *env, uint32_t syndrome)
> > +{
> > +    bool udef;
> > +
> > +    /* We've already checked that EL2 exists at translation time.
> > +     * EL3.HCE has priority over EL2.HCD.
> > +     */
> > +    if (arm_feature(env, ARM_FEATURE_EL3)) {
> > +        udef = !(env->cp15.scr_el3 & SCR_HCE);
> >
> 
> HVC is also undefined if we are in secure state, do we trap this elsewhere?

No, I had originally expected future security-ext patches to fill
the S vs NS gaps but like in other cases I don't mind doing some
preparations.

On AArch64, HVC seems to be allowed from EL3. Adding this for v3:

+    /* In ARMv7 and ARMv8/AArch32, HVC is udef in secure state.
+     * For ARMv8/AArch64, HVC is allowed in EL3.
+     * Note that we've already trapped HVC from EL0 at translation
+     * time.
+     */
+    if (secure && (!is_a64(env) || cur_el == 1)) {
+        udef = true;
+    }


Cheers,
Edgar





> 
> 
> > +    } else {
> > +        udef = env->cp15.hcr_el2 & HCR_HCD;
> > +    }
> > +
> > +    if (udef) {
> > +        env->exception.syndrome = syn_uncategorized();
> > +        raise_exception(env, EXCP_UDEF);
> > +    }
> > +    env->exception.syndrome = syndrome;
> > +    raise_exception(env, EXCP_HVC);
> > +}
> > +
> >  void HELPER(exception_return)(CPUARMState *env)
> >  {
> >      int cur_el = arm_current_pl(env);
> > diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
> > index 3589898..0319061 100644
> > --- a/target-arm/translate-a64.c
> > +++ b/target-arm/translate-a64.c
> > @@ -1434,17 +1434,28 @@ static void disas_exc(DisasContext *s, uint32_t
> > insn)
> >      int opc = extract32(insn, 21, 3);
> >      int op2_ll = extract32(insn, 0, 5);
> >      uint16_t imm16 = extract32(insn, 5, 16);
> > +    TCGv_i32 tmp;
> >
> >      switch (opc) {
> >      case 0:
> > -        /* SVC, HVC, SMC; since we don't support the Virtualization
> > -         * or TrustZone extensions these all UNDEF except SVC.
> > -         */
> > -        if (op2_ll != 1) {
> > +        switch (op2_ll) {
> > +        case 1:
> > +            gen_exception_insn(s, 0, EXCP_SWI, syn_aa64_svc(imm16));
> > +            break;
> > +        case 2:
> > +            if (!arm_dc_feature(s, ARM_FEATURE_EL2) || s->current_pl ==
> > 0) {
> > +                unallocated_encoding(s);
> > +                break;
> > +            }
> > +            tmp = tcg_const_i32(syn_aa64_hvc(imm16));
> > +            gen_a64_set_pc_im(s->pc);
> > +            gen_helper_hvc(cpu_env, tmp);
> > +            tcg_temp_free_i32(tmp);
> > +            break;
> > +        default:
> >              unallocated_encoding(s);
> >              break;
> >          }
> > -        gen_exception_insn(s, 0, EXCP_SWI, syn_aa64_svc(imm16));
> >          break;
> >      case 1:
> >          if (op2_ll != 0) {
> > --
> > 1.8.3.2
> >
> >