Subject: [PATCH v3 26/32] arm64: KVM: 32bit handling of coprocessor traps

From: [email-masked] (Marc Zyngier)
Date: Wed, 24 Apr 2013 14:42:04 +0100

On 24/04/13 00:01, Christoffer Dall wrote:
> On Mon, Apr 08, 2013 at 05:17:28PM +0100, Marc Zyngier wrote:
>> Provide the necessary infrastructure to trap coprocessor accesses that
>> occur when running 32bit guests.
>>
>> Also wire SMC and HVC trapped in 32bit mode while were at it.
>>
>> Reviewed-by: Christopher Covington <[email-masked]>
>> Signed-off-by: Marc Zyngier <[email-masked]>
>> ---
>>  arch/arm64/include/asm/kvm_coproc.h |   5 +
>>  arch/arm64/kvm/handle_exit.c        |   7 ++
>>  arch/arm64/kvm/sys_regs.c           | 178 ++++++++++++++++++++++++++++++++++--
>>  3 files changed, 183 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_coproc.h b/arch/arm64/include/asm/kvm_coproc.h
>> index 9b4477a..9a59301 100644
>> --- a/arch/arm64/include/asm/kvm_coproc.h
>> +++ b/arch/arm64/include/asm/kvm_coproc.h
>> @@ -32,11 +32,16 @@ struct kvm_sys_reg_table {
>>
>>  struct kvm_sys_reg_target_table {
>>       struct kvm_sys_reg_table table64;
>> +     struct kvm_sys_reg_table table32;
>>  };
>>
>>  void kvm_register_target_sys_reg_table(unsigned int target,
>>                                      struct kvm_sys_reg_target_table *table);
>>
>> +int kvm_handle_cp14_load_store(struct kvm_vcpu *vcpu, struct kvm_run *run);
>> +int kvm_handle_cp14_access(struct kvm_vcpu *vcpu, struct kvm_run *run);
>> +int kvm_handle_cp15_32(struct kvm_vcpu *vcpu, struct kvm_run *run);
>> +int kvm_handle_cp15_64(struct kvm_vcpu *vcpu, struct kvm_run *run);
>>  int kvm_handle_sys_reg(struct kvm_vcpu *vcpu, struct kvm_run *run);
>>
>>  #define kvm_coproc_table_init kvm_sys_reg_table_init
>> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
>> index 4766b7f..9beaca03 100644
>> --- a/arch/arm64/kvm/handle_exit.c
>> +++ b/arch/arm64/kvm/handle_exit.c
>> @@ -62,6 +62,13 @@ static int kvm_handle_wfi(struct kvm_vcpu *vcpu, struct kvm_run *run)
>>
>>  static exit_handle_fn arm_exit_handlers[] = {
>>       [ESR_EL2_EC_WFI]        = kvm_handle_wfi,
>> +     [ESR_EL2_EC_CP15_32]    = kvm_handle_cp15_32,
>> +     [ESR_EL2_EC_CP15_64]    = kvm_handle_cp15_64,
>> +     [ESR_EL2_EC_CP14_MR]    = kvm_handle_cp14_access,
>> +     [ESR_EL2_EC_CP14_LS]    = kvm_handle_cp14_load_store,
>> +     [ESR_EL2_EC_CP14_64]    = kvm_handle_cp14_access,
>> +     [ESR_EL2_EC_HVC32]      = handle_hvc,
>> +     [ESR_EL2_EC_SMC32]      = handle_smc,
>>       [ESR_EL2_EC_HVC64]      = handle_hvc,
>>       [ESR_EL2_EC_SMC64]      = handle_smc,
>>       [ESR_EL2_EC_SYS64]      = kvm_handle_sys_reg,
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 9df3b32..0303218 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -38,6 +38,10 @@
>>   * types are different. My gut feeling is that it should be pretty
>>   * easy to merge, but that would be an ABI breakage -- again. VFP
>>   * would also need to be abstracted.
>> + *
>> + * For AArch32, we only take care of what is being trapped. Anything
>> + * that has to do with init and userspace access has to go via the
>> + * 64bit interface.
>>   */
>>
>>  /* 3 bits per cache level, as per CLIDR, but non-existent caches always 0 */
>> @@ -163,6 +167,16 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>       { Op0(0b01), Op1(0b000), CRn(0b0111), CRm(0b1110), Op2(0b010),
>>         access_dcsw },
>>
>> +     /* TEECR32_EL1 */
>> +     { Op0(0b10), Op1(0b010), CRn(0b0000), CRm(0b0000), Op2(0b000),
>> +       NULL, reset_val, TEECR32_EL1, 0 },
>> +     /* TEEHBR32_EL1 */
>> +     { Op0(0b10), Op1(0b010), CRn(0b0001), CRm(0b0000), Op2(0b000),
>> +       NULL, reset_val, TEEHBR32_EL1, 0 },
>> +     /* DBGVCR32_EL2 */
>> +     { Op0(0b10), Op1(0b100), CRn(0b0000), CRm(0b0111), Op2(0b000),
>> +       NULL, reset_val, DBGVCR32_EL2, 0 },
>> +
>>       /* MPIDR_EL1 */
>>       { Op0(0b11), Op1(0b000), CRn(0b0000), CRm(0b0000), Op2(0b101),
>>         NULL, reset_mpidr, MPIDR_EL1 },
>> @@ -273,6 +287,39 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>>       /* TPIDRRO_EL0 */
>>       { Op0(0b11), Op1(0b011), CRn(0b1101), CRm(0b0000), Op2(0b011),
>>         NULL, reset_unknown, TPIDRRO_EL0 },
>> +
>> +     /* DACR32_EL2 */
>> +     { Op0(0b11), Op1(0b100), CRn(0b0011), CRm(0b0000), Op2(0b000),
>> +       NULL, reset_unknown, DACR32_EL2 },
>> +     /* IFSR32_EL2 */
>> +     { Op0(0b11), Op1(0b100), CRn(0b0101), CRm(0b0000), Op2(0b001),
>> +       NULL, reset_unknown, IFSR32_EL2 },
>> +     /* FPEXC32_EL2 */
>> +     { Op0(0b11), Op1(0b100), CRn(0b0101), CRm(0b0011), Op2(0b000),
>> +       NULL, reset_val, FPEXC32_EL2, 0x70 },
>> +};
>> +
>> +/* Trapped cp15 registers */
>> +static const struct sys_reg_desc cp15_regs[] = {
>> +     /*
>> +      * DC{C,I,CI}SW operations:
>> +      */
>> +     { Op1( 0), CRn( 7), CRm( 6), Op2( 2), access_dcsw },
>> +     { Op1( 0), CRn( 7), CRm(10), Op2( 2), access_dcsw },
>> +     { Op1( 0), CRn( 7), CRm(14), Op2( 2), access_dcsw },
>> +     { Op1( 0), CRn( 9), CRm(12), Op2( 0), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(12), Op2( 1), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(12), Op2( 2), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(12), Op2( 3), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(12), Op2( 5), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(12), Op2( 6), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(12), Op2( 7), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(13), Op2( 0), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(13), Op2( 1), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(13), Op2( 2), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(14), Op2( 0), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(14), Op2( 1), pm_fake },
>> +     { Op1( 0), CRn( 9), CRm(14), Op2( 2), pm_fake },
>>  };
>>
>>  /* Target specific emulation tables */
>> @@ -285,13 +332,20 @@ void kvm_register_target_sys_reg_table(unsigned int target,
>>  }
>>
>>  /* Get specific register table for this target. */
>> -static const struct sys_reg_desc *get_target_table(unsigned target, size_t *num)
>> +static const struct sys_reg_desc *get_target_table(unsigned target,
>> +                                                bool mode_is_64,
>> +                                                size_t *num)
>>  {
>>       struct kvm_sys_reg_target_table *table;
>>
>>       table = target_tables[target];
>> -     *num = table->table64.num;
>> -     return table->table64.table;
>> +     if (mode_is_64) {
>> +             *num = table->table64.num;
>> +             return table->table64.table;
>> +     } else {
>> +             *num = table->table32.num;
>> +             return table->table32.table;
>> +     }
>>  }
>>
>>  static const struct sys_reg_desc *find_reg(const struct sys_reg_params *params,
>> @@ -319,13 +373,123 @@ static const struct sys_reg_desc *find_reg(const struct sys_reg_params *params,
>>       return NULL;
>>  }
>>
>> +int kvm_handle_cp14_load_store(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> +{
>> +     kvm_inject_undefined(vcpu);
>> +     return 1;
>> +}
>> +
>> +int kvm_handle_cp14_access(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> +{
>> +     kvm_inject_undefined(vcpu);
>> +     return 1;
>> +}
>> +
>> +static int emulate_cp15(struct kvm_vcpu *vcpu,
>> +                     const struct sys_reg_params *params)
>> +{
>> +     size_t num;
>> +     const struct sys_reg_desc *table, *r;
>> +
>> +     table = get_target_table(vcpu->arch.target, false, &num);
>> +
>> +     /* Search target-specific then generic table. */
>> +     r = find_reg(params, table, num);
>> +     if (!r)
>> +             r = find_reg(params, cp15_regs, ARRAY_SIZE(cp15_regs));
>> +
>> +     if (likely(r)) {
>> +             /* If we don't have an accessor, we should never get here! */
>> +             BUG_ON(!r->access);
> 
> again not quite sure if this warrants a crash of the entire host.
> 
>> +
>> +             if (likely(r->access(vcpu, params, r))) {
>> +                     /* Skip instruction, since it was emulated */
>> +                     kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
>> +                     return 1;
>> +             }
>> +             /* If access function fails, it should complain. */
>> +     } else {
>> +             kvm_err("Unsupported guest CP15 access at: %08lx\n",
>> +                     *vcpu_pc(vcpu));
>> +             print_sys_reg_instr(params);
>> +     }
>> +     kvm_inject_undefined(vcpu);
>> +     return 1;
>> +}
>> +
>> +/**
>> + * kvm_handle_cp15_64 -- handles a mrrc/mcrr trap on a guest CP15 access
>> + * @vcpu: The VCPU pointer
>> + * @run:  The kvm_run struct
>> + */
>> +int kvm_handle_cp15_64(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> +{
>> +     struct sys_reg_params params;
>> +     u32 hsr = kvm_vcpu_get_hsr(vcpu);
>> +     int Rt2 = (hsr >> 10) & 0xf;
>> +     int ret;
>> +
>> +     params.CRm = (hsr >> 1) & 0xf;
>> +     params.Rt = (hsr >> 5) & 0xf;
>> +     params.is_write = ((hsr & 1) == 0);
>> +
>> +     params.Op0 = 0;
>> +     params.Op1 = (hsr >> 16) & 0xf;
>> +     params.Op2 = 0;
>> +     params.CRn = 0;
>> +
>> +     /*
>> +      * Massive hack here. Store Rt2 in the top 32bits so we only
>> +      * have one register to deal with. As we use the same trap
>> +      * backends between AArch32 and AArch64, we get away with it.
>> +      */
>> +     if (params.is_write) {
>> +             u64 val = *vcpu_reg(vcpu, params.Rt);
>> +             val &= 0xffffffff;
>> +             val |= *vcpu_reg(vcpu, Rt2) << 32;
>> +             *vcpu_reg(vcpu, params.Rt) = val;
>> +     }
>> +
>> +     ret = emulate_cp15(vcpu, &params);
>> +
>> +     /* Reverse hack here */
> 
> nit: consider changing the wording to something like 'Similar hack for
> reads here', so readers don't think you are trying to reverse the hack
> you did above.

Sure.

>> +     if (ret && !params.is_write) {
>> +             u64 val = *vcpu_reg(vcpu, params.Rt);
>> +             val >>= 32;
>> +             *vcpu_reg(vcpu, Rt2) = val;
> 
> actually the emulate_cp15 should probably be turned into a void and the
> ret check could go away, same thing on the 32-bit side.

Well, if we don't BUG_ON() in emulate_cp15, then we do want to return
something that meaningfully shown that we failed to handle the trap.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...