Re: [PATCH v6 15/15] iommu/vt-d: Support reporting nesting capability info

Auger Eric
2020-08-17T07:43:21Z

On 8/17/20 9:05 AM, Liu, Yi L wrote:
> Hi Eric,
>
>> Auger Eric <eric.auger@redhat.com>
>> Sent: Sunday, August 16, 2020 8:01 PM
>>
>> Hi Yi,
>>
>> On 7/28/20 8:27 AM, Liu Yi L wrote:
>>> This patch reports nesting info, and only supports the case where all
>>> the physical iomms have the same CAP/ECAP MASKS.
>> s/iomms/iommus
>
> yep.
>
>>>
>>> Cc: Kevin Tian <kevin.tian@intel.com>
>>> CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
>>> Cc: Alex Williamson <alex.williamson@redhat.com>
>>> Cc: Eric Auger <eric.auger@redhat.com>
>>> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
>>> Cc: Joerg Roedel <joro@8bytes.org>
>>> Cc: Lu Baolu <baolu.lu@linux.intel.com>
>>> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
>>> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
>>> ---
>>> v2 -> v3:
>>> *) remove cap/ecap_mask in iommu_nesting_info.
>>> ---
>>> drivers/iommu/intel/iommu.c | 81
>> +++++++++++++++++++++++++++++++++++++++++++--
>>> include/linux/intel-iommu.h | 16 +++++++++
>>> 2 files changed, 95 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>> index 88f4647..0835804 100644
>>> --- a/drivers/iommu/intel/iommu.c
>>> +++ b/drivers/iommu/intel/iommu.c
>>> @@ -5660,12 +5660,16 @@ static inline bool iommu_pasid_support(void)
>>> static inline bool nested_mode_support(void)
>>> {
>>> struct dmar_drhd_unit *drhd;
>>> - struct intel_iommu *iommu;
>>> + struct intel_iommu *iommu, *prev = NULL;
>>> bool ret = true;
>>>
>>> rcu_read_lock();
>>> for_each_active_iommu(iommu, drhd) {
>>> - if (!sm_supported(iommu) || !ecap_nest(iommu->ecap)) {
>>> + if (!prev)
>>> + prev = iommu;
>>> + if (!sm_supported(iommu) || !ecap_nest(iommu->ecap) ||
>>> + (VTD_CAP_MASK & (iommu->cap ^ prev->cap)) ||
>>> + (VTD_ECAP_MASK & (iommu->ecap ^ prev->ecap))) {
>>> ret = false;
>>> break;
>> So this changes the behavior of DOMAIN_ATTR_NESTING. Shouldn't it have a
>> Fixes tag as well? And maybe add the capability getter in a separate patch?
>
> yes, this changed the behavior. so it would be better to be a separate patch
> and upstream along? how about your idea? @Lu, Baolu :-)
>
>>> }
>>> @@ -6081,6 +6085,78 @@ intel_iommu_domain_set_attr(struct iommu_domain
>> *domain,
>>> return ret;
>>> }
>>>
>>> +static int intel_iommu_get_nesting_info(struct iommu_domain *domain,
>>> + struct iommu_nesting_info *info)
>>> +{
>>> + struct dmar_domain *dmar_domain = to_dmar_domain(domain);
>>> + u64 cap = VTD_CAP_MASK, ecap = VTD_ECAP_MASK;
>>> + struct device_domain_info *domain_info;
>>> + struct iommu_nesting_info_vtd vtd;
>>> + unsigned long flags;
>>> + unsigned int size;
>>> +
>
> perhaps better to acquire the lock here. [1]
>
>>> + if (domain->type != IOMMU_DOMAIN_UNMANAGED ||
>>> + !(dmar_domain->flags & DOMAIN_FLAG_NESTING_MODE))
>>> + return -ENODEV;
>>> +
>>> + if (!info)
>>> + return -EINVAL;
>>> +
>>> + size = sizeof(struct iommu_nesting_info) +
>>> + sizeof(struct iommu_nesting_info_vtd);
>>> + /*
>>> + * if provided buffer size is smaller than expected, should
>>> + * return 0 and also the expected buffer size to caller.
>>> + */
>>> + if (info->argsz < size) {
>>> + info->argsz = size;
>>> + return 0;
>>> + }
>>> +
>>> + spin_lock_irqsave(&device_domain_lock, flags);
>>> + /*
>>> + * arbitrary select the first domain_info as all nesting
>>> + * related capabilities should be consistent across iommu
>>> + * units.
>>> + */
>>> + domain_info = list_first_entry(&dmar_domain->devices,
>>> + struct device_domain_info, link);
>>> + cap &= domain_info->iommu->cap;
>>> + ecap &= domain_info->iommu->ecap;
>>> + spin_unlock_irqrestore(&device_domain_lock, flags);
>>> +
>>> + info->format = IOMMU_PASID_FORMAT_INTEL_VTD;
>>> + info->features = IOMMU_NESTING_FEAT_SYSWIDE_PASID |
>>> + IOMMU_NESTING_FEAT_BIND_PGTBL |
>>> + IOMMU_NESTING_FEAT_CACHE_INVLD;
>>> + info->addr_width = dmar_domain->gaw;
>>> + info->pasid_bits = ilog2(intel_pasid_max_id);
>>> + info->padding = 0;
>>> + vtd.flags = 0;
>>> + vtd.padding = 0;
>>> + vtd.cap_reg = cap;
>>> + vtd.ecap_reg = ecap;
>>> +
>>> + memcpy(info->data, &vtd, sizeof(vtd));
>>> + return 0;
>>> +}
>>> +
>>> +static int intel_iommu_domain_get_attr(struct iommu_domain *domain,
>>> + enum iommu_attr attr, void *data)
>>> +{
>>> + switch (attr) {
>>> + case DOMAIN_ATTR_NESTING:
>>> + {
>>> + struct iommu_nesting_info *info =
>>> + (struct iommu_nesting_info *)data;
>>
>> don't you need to hold a device_domain_lock earlier to make sure domain
>> attributes can't change behind your back (unmanaged type and nested mode)?
>
> do you mean acquire lock at [1]?
yep either at [1] or before calling intel_iommu_get_nesting_info and
adding a comment saying intel_iommu_get_nesting_info() shall be called
with the lock held

Thanks

Eric
>
> Regards,
> Yi Liu
>
>>> +
>>> + return intel_iommu_get_nesting_info(domain, info);
>>> + }
>>> + default:
>>> + return -ENOENT;
>>> + }
>>> +}
>>> +
>>> /*
>>> * Check that the device does not live on an external facing PCI port that is
>>> * marked as untrusted. Such devices should not be able to apply quirks and
>>> @@ -6103,6 +6179,7 @@ const struct iommu_ops intel_iommu_ops = {
>>> .domain_alloc = intel_iommu_domain_alloc,
>>> .domain_free = intel_iommu_domain_free,
>>> .domain_set_attr = intel_iommu_domain_set_attr,
>>> + .domain_get_attr = intel_iommu_domain_get_attr,
>>> .attach_dev = intel_iommu_attach_device,
>>> .detach_dev = intel_iommu_detach_device,
>>> .aux_attach_dev = intel_iommu_aux_attach_device,
>>> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
>>> index f98146b..5acf795 100644
>>> --- a/include/linux/intel-iommu.h
>>> +++ b/include/linux/intel-iommu.h
>>> @@ -197,6 +197,22 @@
>>> #define ecap_max_handle_mask(e) ((e >> 20) & 0xf)
>>> #define ecap_sc_support(e) ((e >> 7) & 0x1) /* Snooping Control */
>>>
>>> +/* Nesting Support Capability Alignment */
>>> +#define VTD_CAP_FL1GP BIT_ULL(56)
>>> +#define VTD_CAP_FL5LP BIT_ULL(60)
>>> +#define VTD_ECAP_PRS BIT_ULL(29)
>>> +#define VTD_ECAP_ERS BIT_ULL(30)
>>> +#define VTD_ECAP_SRS BIT_ULL(31)
>>> +#define VTD_ECAP_EAFS BIT_ULL(34)
>>> +#define VTD_ECAP_PASID BIT_ULL(40)
>>> +
>>> +/* Only capabilities marked in below MASKs are reported */
>>> +#define VTD_CAP_MASK (VTD_CAP_FL1GP | VTD_CAP_FL5LP)
>>> +
>>> +#define VTD_ECAP_MASK (VTD_ECAP_PRS | VTD_ECAP_ERS | \
>>> + VTD_ECAP_SRS | VTD_ECAP_EAFS | \
>>> + VTD_ECAP_PASID)
>>> +
>>> /* Virtual command interface capability */
>>> #define vccap_pasid(v) (((v) & DMA_VCS_PAS)) /* PASID allocation
>> */
>>>
>>>
>> Thanks
>>
>> Eric