Re: [PATCH v2] target/arm: Add raw_writes ops for register whose write induce TLB maintenance

[Eric Auger <eric.auger@redhat.com>]

Hi Peter,

On 2/16/23 14:51, Peter Maydell wrote:
> On Mon, 13 Feb 2023 at 18:38, Eric Auger <eric.auger@redhat.com> wrote:
>> Some registers whose 'cooked' writefns induce TLB maintenance do
>> not have raw_writefn ops defined. If only the writefn ops is set
>> (ie. no raw_writefn is provided), it is assumed the cooked also
>> work as the raw one. For those registers it is not obvious the
>> tlb_flush works on KVM mode so better/safer setting the raw write.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
>>
>> ---
>>
>> v1 -> v2:
>> - do not add raw_writefn if type is set to ARM_CP_NO_RAW [Peter]
>>
>> I am not familiar with those callbacks. I am not sure whether
>> the .raw_writefn must be set only for registers only doing some
>> TLB maintenance or shall be set safely on other registers doing
>> TLB maintenance + other state settings.
>> ---
>>  target/arm/helper.c | 39 +++++++++++++++++++++++----------------
>>  1 file changed, 23 insertions(+), 16 deletions(-)
>>
>> diff --git a/target/arm/helper.c b/target/arm/helper.c
>> index c62ed05c12..0bd8806999 100644
>> --- a/target/arm/helper.c
>> +++ b/target/arm/helper.c
>> @@ -719,16 +719,20 @@ static const ARMCPRegInfo not_v7_cp_reginfo[] = {
>>       * the unified TLB ops but also the dside/iside/inner-shareable variants.
>>       */
>>      { .name = "TLBIALL", .cp = 15, .crn = 8, .crm = CP_ANY,
>> -      .opc1 = CP_ANY, .opc2 = 0, .access = PL1_W, .writefn = tlbiall_write,
>> +      .opc1 = CP_ANY, .opc2 = 0, .access = PL1_W,
>> +      .writefn = tlbiall_write, .raw_writefn = raw_write,
>>        .type = ARM_CP_NO_RAW },
>>      { .name = "TLBIMVA", .cp = 15, .crn = 8, .crm = CP_ANY,
>> -      .opc1 = CP_ANY, .opc2 = 1, .access = PL1_W, .writefn = tlbimva_write,
>> +      .opc1 = CP_ANY, .opc2 = 1, .access = PL1_W,
>> +      .writefn = tlbimva_write, .raw_writefn = raw_write,
>>        .type = ARM_CP_NO_RAW },
>>      { .name = "TLBIASID", .cp = 15, .crn = 8, .crm = CP_ANY,
>> -      .opc1 = CP_ANY, .opc2 = 2, .access = PL1_W, .writefn = tlbiasid_write,
>> +      .opc1 = CP_ANY, .opc2 = 2, .access = PL1_W,
>> +      .writefn = tlbiasid_write, .raw_writefn = raw_write,
>>        .type = ARM_CP_NO_RAW },
>>      { .name = "TLBIMVAA", .cp = 15, .crn = 8, .crm = CP_ANY,
>> -      .opc1 = CP_ANY, .opc2 = 3, .access = PL1_W, .writefn = tlbimvaa_write,
>> +      .opc1 = CP_ANY, .opc2 = 3, .access = PL1_W,
>> +      .writefn = tlbimvaa_write, .raw_writefn = raw_write,
>>        .type = ARM_CP_NO_RAW },
>>      { .name = "PRRR", .cp = 15, .crn = 10, .crm = 2,
>>        .opc1 = 0, .opc2 = 0, .access = PL1_RW, .type = ARM_CP_NOP },
> These are all type ARM_CP_NO_RAW, so don't want a raw_writefn.
damned, need to change my eyes :-(
>
>> @@ -4183,14 +4187,14 @@ static const ARMCPRegInfo vmsa_cp_reginfo[] = {
>>        .opc0 = 3, .opc1 = 0, .crn = 2, .crm = 0, .opc2 = 0,
>>        .access = PL1_RW, .accessfn = access_tvm_trvm,
>>        .fgt = FGT_TTBR0_EL1,
>> -      .writefn = vmsa_ttbr_write, .resetvalue = 0,
>> +      .writefn = vmsa_ttbr_write, .resetvalue = 0, .raw_writefn = raw_write,
>>        .bank_fieldoffsets = { offsetof(CPUARMState, cp15.ttbr0_s),
>>                               offsetof(CPUARMState, cp15.ttbr0_ns) } },
>>      { .name = "TTBR1_EL1", .state = ARM_CP_STATE_BOTH,
>>        .opc0 = 3, .opc1 = 0, .crn = 2, .crm = 0, .opc2 = 1,
>>        .access = PL1_RW, .accessfn = access_tvm_trvm,
>>        .fgt = FGT_TTBR1_EL1,
>> -      .writefn = vmsa_ttbr_write, .resetvalue = 0,
>> +      .writefn = vmsa_ttbr_write, .resetvalue = 0, .raw_writefn = raw_write,
>>        .bank_fieldoffsets = { offsetof(CPUARMState, cp15.ttbr1_s),
>>                               offsetof(CPUARMState, cp15.ttbr1_ns) } },
>>      { .name = "TCR_EL1", .state = ARM_CP_STATE_AA64,
>> @@ -4450,13 +4454,13 @@ static const ARMCPRegInfo lpae_cp_reginfo[] = {
>>        .type = ARM_CP_64BIT | ARM_CP_ALIAS,
>>        .bank_fieldoffsets = { offsetof(CPUARMState, cp15.ttbr0_s),
>>                               offsetof(CPUARMState, cp15.ttbr0_ns) },
>> -      .writefn = vmsa_ttbr_write, },
>> +      .writefn = vmsa_ttbr_write, .raw_writefn = raw_write },
>>      { .name = "TTBR1", .cp = 15, .crm = 2, .opc1 = 1,
>>        .access = PL1_RW, .accessfn = access_tvm_trvm,
>>        .type = ARM_CP_64BIT | ARM_CP_ALIAS,
>>        .bank_fieldoffsets = { offsetof(CPUARMState, cp15.ttbr1_s),
>>                               offsetof(CPUARMState, cp15.ttbr1_ns) },
>> -      .writefn = vmsa_ttbr_write, },
>> +      .writefn = vmsa_ttbr_write, .raw_writefn = raw_write },
>>  };
>>
>>  static uint64_t aa64_fpcr_read(CPUARMState *env, const ARMCPRegInfo *ri)
>> @@ -5899,12 +5903,12 @@ static const ARMCPRegInfo el2_cp_reginfo[] = {
>>        .type = ARM_CP_IO,
>>        .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 0,
>>        .access = PL2_RW, .fieldoffset = offsetof(CPUARMState, cp15.hcr_el2),
>> -      .writefn = hcr_write },
>> +      .writefn = hcr_write, .raw_writefn = raw_write },
> These ones are OK.
>
>>      { .name = "HCR", .state = ARM_CP_STATE_AA32,
>>        .type = ARM_CP_ALIAS | ARM_CP_IO,
>>        .cp = 15, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 0,
>>        .access = PL2_RW, .fieldoffset = offsetof(CPUARMState, cp15.hcr_el2),
>> -      .writefn = hcr_writelow },
>> +      .writefn = hcr_writelow, .raw_writefn = raw_write },
> This is going to do the wrong thing on big-endian hosts, because
> the data value is the low 32 bits and the raw_writefn will
> write that to the whole 64-bit value. We could implement a
> special purpose raw write for this register which just writes
> the value to the low 32 bits, I guess.
>
> For KVM we could ignore this, though -- the register is EL2 only,
> and also is ARM_CP_ALIAS, which means we won't try to do anything
> with it for the KVM<->QEMU state sync or the migration codepaths.
OK so can I simply revert that change.
>
>>      { .name = "HACR_EL2", .state = ARM_CP_STATE_BOTH,
>>        .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 7,
>>        .access = PL2_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
>> @@ -5971,6 +5975,7 @@ static const ARMCPRegInfo el2_cp_reginfo[] = {
>>      { .name = "TCR_EL2", .state = ARM_CP_STATE_BOTH,
>>        .opc0 = 3, .opc1 = 4, .crn = 2, .crm = 0, .opc2 = 2,
>>        .access = PL2_RW, .writefn = vmsa_tcr_el12_write,
>> +      .raw_writefn = raw_write,
>>        .fieldoffset = offsetof(CPUARMState, cp15.tcr_el[2]) },
>>      { .name = "VTCR", .state = ARM_CP_STATE_AA32,
>>        .cp = 15, .opc1 = 4, .crn = 2, .crm = 1, .opc2 = 2,
>> @@ -5987,10 +5992,10 @@ static const ARMCPRegInfo el2_cp_reginfo[] = {
>>        .type = ARM_CP_64BIT | ARM_CP_ALIAS,
>>        .access = PL2_RW, .accessfn = access_el3_aa32ns,
>>        .fieldoffset = offsetof(CPUARMState, cp15.vttbr_el2),
>> -      .writefn = vttbr_write },
>> +      .writefn = vttbr_write, .raw_writefn = raw_write },
>>      { .name = "VTTBR_EL2", .state = ARM_CP_STATE_AA64,
>>        .opc0 = 3, .opc1 = 4, .crn = 2, .crm = 1, .opc2 = 0,
>> -      .access = PL2_RW, .writefn = vttbr_write,
>> +      .access = PL2_RW, .writefn = vttbr_write, .raw_writefn = raw_write,
>>        .fieldoffset = offsetof(CPUARMState, cp15.vttbr_el2) },
>>      { .name = "SCTLR_EL2", .state = ARM_CP_STATE_BOTH,
>>        .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 0, .opc2 = 0,
>> @@ -6002,7 +6007,8 @@ static const ARMCPRegInfo el2_cp_reginfo[] = {
>>        .fieldoffset = offsetof(CPUARMState, cp15.tpidr_el[2]) },
>>      { .name = "TTBR0_EL2", .state = ARM_CP_STATE_AA64,
>>        .opc0 = 3, .opc1 = 4, .crn = 2, .crm = 0, .opc2 = 0,
>> -      .access = PL2_RW, .resetvalue = 0, .writefn = vmsa_tcr_ttbr_el2_write,
>> +      .access = PL2_RW, .resetvalue = 0,
>> +      .writefn = vmsa_tcr_ttbr_el2_write, .raw_writefn = raw_write,
>>        .fieldoffset = offsetof(CPUARMState, cp15.ttbr0_el[2]) },
>>      { .name = "HTTBR", .cp = 15, .opc1 = 4, .crm = 2,
>>        .access = PL2_RW, .type = ARM_CP_64BIT | ARM_CP_ALIAS,
> These ones are all OK.
>
>> @@ -6139,7 +6145,7 @@ static const ARMCPRegInfo el2_v8_cp_reginfo[] = {
>>        .cp = 15, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 4,
>>        .access = PL2_RW,
>>        .fieldoffset = offsetofhigh32(CPUARMState, cp15.hcr_el2),
>> -      .writefn = hcr_writehigh },
>> +      .writefn = hcr_writehigh, .raw_writefn = raw_write },
> Similarly this would need a special purpose raw write function
> since we want to only touch the high 32 bits; and again for
> the KVM case we won't ever be doing a raw access to this register.

same question: can I simply revert that change?

>
>
>>  };
>>
>>  static CPAccessResult sel2_access(CPUARMState *env, const ARMCPRegInfo *ri,
>> @@ -6189,12 +6195,12 @@ static const ARMCPRegInfo el3_cp_reginfo[] = {
>>      { .name = "SCR_EL3", .state = ARM_CP_STATE_AA64,
>>        .opc0 = 3, .opc1 = 6, .crn = 1, .crm = 1, .opc2 = 0,
>>        .access = PL3_RW, .fieldoffset = offsetof(CPUARMState, cp15.scr_el3),
>> -      .resetfn = scr_reset, .writefn = scr_write },
>> +      .resetfn = scr_reset, .writefn = scr_write, .raw_writefn = raw_write },
>>      { .name = "SCR",  .type = ARM_CP_ALIAS | ARM_CP_NEWEL,
>>        .cp = 15, .opc1 = 0, .crn = 1, .crm = 1, .opc2 = 0,
>>        .access = PL1_RW, .accessfn = access_trap_aa32s_el1,
>>        .fieldoffset = offsetoflow32(CPUARMState, cp15.scr_el3),
>> -      .writefn = scr_write },
>> +      .writefn = scr_write, .raw_writefn = raw_write },
>>      { .name = "SDER32_EL3", .state = ARM_CP_STATE_AA64,
>>        .opc0 = 3, .opc1 = 6, .crn = 1, .crm = 1, .opc2 = 1,
>>        .access = PL3_RW, .resetvalue = 0,
>> @@ -7862,6 +7868,7 @@ static const ARMCPRegInfo vhe_reginfo[] = {
>>      { .name = "TTBR1_EL2", .state = ARM_CP_STATE_AA64,
>>        .opc0 = 3, .opc1 = 4, .crn = 2, .crm = 0, .opc2 = 1,
>>        .access = PL2_RW, .writefn = vmsa_tcr_ttbr_el2_write,
>> +      .raw_writefn = raw_write,
>>        .fieldoffset = offsetof(CPUARMState, cp15.ttbr1_el[2]) },
> These are OK.

Than you for the review!

Eric
>
>>  #ifndef CONFIG_USER_ONLY
>>      { .name = "CNTHV_CVAL_EL2", .state = ARM_CP_STATE_AA64,
>> --
>> 2.37.3
>>
> thanks
> -- PMM
>