Hi Drew, On 9/26/19 1:40 PM, Andrew Jones wrote: > On Thu, Sep 26, 2019 at 12:01:36PM +0200, Auger Eric wrote: >> >> >> On 9/26/19 10:41 AM, Andrew Jones wrote: >>> On Thu, Sep 26, 2019 at 08:52:55AM +0200, Auger Eric wrote: >>>> Hi Drew, >>>> >>>> On 9/24/19 1:31 PM, Andrew Jones wrote: >>>>> Extend the SVE vq map initialization and validation with KVM's >>>>> supported vector lengths when KVM is enabled. In order to determine >>>>> and select supported lengths we add two new KVM functions for getting >>>>> and setting the KVM_REG_ARM64_SVE_VLS pseudo-register. >>>>> >>>>> This patch has been co-authored with Richard Henderson, who reworked >>>>> the target/arm/cpu64.c changes in order to push all the validation and >>>>> auto-enabling/disabling steps into the finalizer, resulting in a nice >>>>> LOC reduction. >>>>> >>>>> Signed-off-by: Andrew Jones <[email protected]> >>>>> --- >>>>> docs/arm-cpu-features.rst | 36 +++++--- >>>>> target/arm/cpu64.c | 167 +++++++++++++++++++++++++++++--------- >>>>> target/arm/kvm64.c | 100 ++++++++++++++++++++++- >>>>> target/arm/kvm_arm.h | 12 +++ >>>>> tests/arm-cpu-features.c | 105 +++++++++++++++++++++++- >>>>> 5 files changed, 368 insertions(+), 52 deletions(-) >>>>> >>>>> diff --git a/docs/arm-cpu-features.rst b/docs/arm-cpu-features.rst >>>>> index 1262fddc6201..939366f959cf 100644 >>>>> --- a/docs/arm-cpu-features.rst >>>>> +++ b/docs/arm-cpu-features.rst >>>>> @@ -188,10 +188,17 @@ SVE CPU Property Dependencies and Constraints >>>>> >>>>> 1) At least one vector length must be enabled when `sve` is enabled. >>>>> >>>>> - 2) If a vector length `N` is enabled, then all power-of-two vector >>>>> - lengths smaller than `N` must also be enabled. E.g. if `sve512` >>>>> - is enabled, then `sve128` and `sve256` must also be enabled, >>>>> - but `sve384` is not required. >>>>> + 2) If a vector length `N` is enabled, then, when KVM is enabled, all >>>>> + smaller, host supported vector lengths must also be enabled. If >>>>> + KVM is not enabled, then only all the smaller, power-of-two vector >>>>> + lengths must be enabled. E.g. with KVM if the host supports all >>>>> + vector lengths up to 512-bits (128, 256, 384, 512), then if >>>>> + `sve512` is enabled, `sve128`, `sve256`, and `sve384` must also >>>>> + be enabled. Without KVM, `sve384` would not be required. >>>>> + >>>>> + 3) If KVM is enabled then only vector lengths that the host CPU type >>>>> + support may be enabled. If SVE is not supported by the host, then >>>>> + no `sve*` properties may be enabled. >>>>> >>>>> SVE CPU Property Parsing Semantics >>>>> ---------------------------------- >>>>> @@ -210,20 +217,29 @@ SVE CPU Property Parsing Semantics >>>>> disable the last enabled vector length (see constraint (1) of "SVE >>>>> CPU Property Dependencies and Constraints"). >>>>> >>>>> - 4) If one or more `sve<N>` CPU properties are set `off`, but no >>>>> `sve<N>`, >>>>> + 4) When KVM is enabled, if the host does not support SVE, then an error >>>>> + is generated when attempting to enable any `sve*` properties. >>>>> + >>>>> + 5) When KVM is enabled, if the host does support SVE, then an error is >>>>> + generated when attempting to enable any vector lengths not supported >>>>> + by the host. >>>>> + >>>>> + 6) If one or more `sve<N>` CPU properties are set `off`, but no >>>>> `sve<N>`, >>>>> CPU properties are set `on`, then the specified vector lengths are >>>>> disabled but the default for any unspecified lengths remains >>>>> enabled. >>>>> - Disabling a power-of-two vector length also disables all vector >>>>> - lengths larger than the power-of-two length (see constraint (2) of >>>>> - "SVE CPU Property Dependencies and Constraints"). >>>>> + When KVM is not enabled, disabling a power-of-two vector length also >>>>> + disables all vector lengths larger than the power-of-two length. >>>>> + When KVM is enabled, then disabling any supported vector length also >>>>> + disables all larger vector lengths (see constraint (2) of "SVE CPU >>>>> + Property Dependencies and Constraints"). >>>>> >>>>> - 5) If one or more `sve<N>` CPU properties are set to `on`, then they >>>>> + 7) If one or more `sve<N>` CPU properties are set to `on`, then they >>>>> are enabled and all unspecified lengths default to disabled, except >>>>> for the required lengths per constraint (2) of "SVE CPU Property >>>>> Dependencies and Constraints", which will even be auto-enabled if >>>>> they were not explicitly enabled. >>>>> >>>>> - 6) If SVE was disabled (`sve=off`), allowing all vector lengths to be >>>>> + 8) If SVE was disabled (`sve=off`), allowing all vector lengths to be >>>>> explicitly disabled (i.e. avoiding the error specified in (3) of >>>>> "SVE CPU Property Parsing Semantics"), then if later an `sve=on` is >>>>> provided an error will be generated. To avoid this error, one must >>>>> diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c >>>>> index b7eff4e1e107..18dd5e24ec61 100644 >>>>> --- a/target/arm/cpu64.c >>>>> +++ b/target/arm/cpu64.c >>>>> @@ -273,9 +273,18 @@ void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp) >>>>> * any of the above. Finally, if SVE is not disabled, then at least >>>>> one >>>>> * vector length must be enabled. >>>>> */ >>>>> + DECLARE_BITMAP(kvm_supported, ARM_MAX_VQ); >>>>> DECLARE_BITMAP(tmp, ARM_MAX_VQ); >>>>> uint32_t vq, max_vq = 0; >>>>> >>>>> + /* Collect the set of vector lengths supported by KVM. */ >>>>> + bitmap_zero(kvm_supported, ARM_MAX_VQ); >>>>> + if (kvm_enabled() && kvm_arm_sve_supported(CPU(cpu))) { >>>>> + kvm_arm_sve_get_vls(CPU(cpu), kvm_supported); >>>>> + } else if (kvm_enabled()) { >>>>> + assert(!cpu_isar_feature(aa64_sve, cpu)); >>>> why not set an error and propagate it instead? >>> >>> This should never happen. We shouldn't be here if KVM is enabled and SVE >>> isn't supported. The question is how defensive do we want QEMU code? >>> We could just drop the check altogether if we don't want the assert, but >>> I'd rather keep it. >>> >>>>> + } >>>>> + >>>>> /* >>>>> * Process explicit sve<N> properties. >>>>> * From the properties, sve_vq_map<N> implies sve_vq_init<N>. >>>>> @@ -293,10 +302,19 @@ void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp) >>>>> return; >>>>> } >>>>> >>>>> - /* Propagate enabled bits down through required powers-of-two. */ >>>>> - for (vq = pow2floor(max_vq); vq >= 1; vq >>= 1) { >>>>> - if (!test_bit(vq - 1, cpu->sve_vq_init)) { >>>>> - set_bit(vq - 1, cpu->sve_vq_map); >>>>> + if (kvm_enabled()) { >>>>> + /* >>>>> + * For KVM we have to automatically enable all supported >>>>> unitialized >>>>> + * lengths, even when the smaller lengths are not all >>>>> powers-of-two. >>>>> + */ >>>>> + bitmap_andnot(tmp, kvm_supported, cpu->sve_vq_init, max_vq); >>>>> + bitmap_or(cpu->sve_vq_map, cpu->sve_vq_map, tmp, max_vq); >>>>> + } else { >>>>> + /* Propagate enabled bits down through required >>>>> powers-of-two. */ >>>>> + for (vq = pow2floor(max_vq); vq >= 1; vq >>= 1) { >>>>> + if (!test_bit(vq - 1, cpu->sve_vq_init)) { >>>>> + set_bit(vq - 1, cpu->sve_vq_map); >>>>> + } >>>>> } >>>>> } >>>>> } else if (cpu->sve_max_vq == 0) { >>>>> @@ -308,23 +326,46 @@ void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp) >>>>> return; >>>>> } >>>>> >>>>> - /* Disabling a power-of-two disables all larger lengths. */ >>>>> - if (test_bit(0, cpu->sve_vq_init)) { >>>>> - error_setg(errp, "cannot disable sve128"); >>>>> - error_append_hint(errp, "Disabling sve128 results in all >>>>> vector " >>>>> - "lengths being disabled.\n"); >>>>> - error_append_hint(errp, "With SVE enabled, at least one >>>>> vector " >>>>> - "length must be enabled.\n"); >>>>> - return; >>>>> - } >>>>> - for (vq = 2; vq <= ARM_MAX_VQ; vq <<= 1) { >>>>> - if (test_bit(vq - 1, cpu->sve_vq_init)) { >>>>> - break; >>>>> + if (kvm_enabled()) { >>>>> + /* Disabling a supported length disables all larger lengths. >>>>> */ >>>>> + for (vq = 1; vq <= ARM_MAX_VQ; ++vq) { >>>>> + if (test_bit(vq - 1, cpu->sve_vq_init) && >>>>> + test_bit(vq - 1, kvm_supported)) { >>>>> + break; >>>>> + } >> the above loop looks for the 1st disabled vq that is also supported, right? > > Right > >>>>> + } >>>>> + max_vq = vq <= ARM_MAX_VQ ? vq - 1 : ARM_MAX_VQ; >>>>> + bitmap_andnot(cpu->sve_vq_map, kvm_supported, >>>>> + cpu->sve_vq_init, max_vq); >>>>> + if (max_vq == 0 || bitmap_empty(cpu->sve_vq_map, max_vq)) { >> here we don't have anything enabled below the disabled one. So don't we >> have the culprit already? > > Oh, you're right. We can drop the find_next_bit call. Thanks for catching > that. > >>>>> + vq = find_next_bit(kvm_supported, ARM_MAX_VQ, 0) + 1; >>>>> + error_setg(errp, "cannot disable sve%d", vq * 128); >>>> isn't the one disabled max_vq? Do you really need to re-compute vq? > > vq != max_vq here. max_vq is one smaller, even 0 if vq=1. So while vq > is already correct, as you've pointed out, we need to use specifically > that, not max_vq. OK
Thanks Eric > > Thanks, > drew >
