Re: [PATCH v2 09/19] iommu/vt-d: Enlightened PASID allocation

Auger Eric
2019-04-26T07:24:39Z

On 4/26/19 1:40 AM, Jacob Pan wrote:
> On Wed, 24 Apr 2019 19:27:52 +0200
> Auger Eric <eric.auger@redhat.com> wrote:
>
>> Hi Jacob,
>>
>> On 4/24/19 1:31 AM, Jacob Pan wrote:
>>> From: Lu Baolu <baolu.lu@linux.intel.com>
>>>
>>> If Intel IOMMU runs in caching mode, a.k.a. virtual IOMMU, the
>>> IOMMU driver should rely on the emulation software to allocate
>>> and free PASID IDs.
>> Do we make the decision depending on the CM or depending on the
>> VCCAP_REG?
>>
>> VCCAP_REG description says:
>>
>> If Set, software must use Virtual Command Register interface to
>> allocate and free PASIDs.
>>
>> The Intel vt-d spec revision 3.0 defines a
>>> register set to support this. This includes a capability register,
>>> a virtual command register and a virtual response register. Refer
>>> to section 10.4.42, 10.4.43, 10.4.44 for more information.
>>>
>>> This patch adds the enlightened PASID allocation/free interfaces
>> For mu curiosity why is it called "enlightened"?
> I don't know the origin but "enlightened" means guest is tipped with
> information that it is not running on real HW.
>
>>> via the virtual command register.
>>>
>>> Cc: Ashok Raj <ashok.raj@intel.com>
>>> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
>>> Cc: Kevin Tian <kevin.tian@intel.com>
>>> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
>>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>>> ---
>>> drivers/iommu/intel-pasid.c | 70
>>> +++++++++++++++++++++++++++++++++++++++++++++
>>> drivers/iommu/intel-pasid.h | 13 ++++++++-
>>> include/linux/intel-iommu.h | 2 ++ 3 files changed, 84
>>> insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/iommu/intel-pasid.c
>>> b/drivers/iommu/intel-pasid.c index 03b12d2..5b1d3be 100644
>>> --- a/drivers/iommu/intel-pasid.c
>>> +++ b/drivers/iommu/intel-pasid.c
>>> @@ -63,6 +63,76 @@ void *intel_pasid_lookup_id(int pasid)
>>> return p;
>>> }
>>>
>>> +int vcmd_alloc_pasid(struct intel_iommu *iommu, unsigned int
>>> *pasid) +{
>>> + u64 res;
>>> + u64 cap;
>>> + u8 err_code;
>>> + unsigned long flags;
>>> + int ret = 0;
>>> +
>>> + if (!ecap_vcs(iommu->ecap)) {
>>> + pr_warn("IOMMU: %s: Hardware doesn't support
>>> virtual command\n",
>>> + iommu->name);
>> nit: other pr_* messages don't have the "IOMMU: %s:" prefix.
> Are you suggesting just use the prefix defined in pr_fmt? I guess i can
> remove "IOMMU" if Allen is OK with it :).
I aimed to signal the trace formats are not homogeneous in this .c file
but that's not a big deal. In the feature you may use the "IOMMU: %s"
prefix for all pr_* traces.

>
>>> + return -ENODEV;
>>> + }
>>> +
>>> + cap = dmar_readq(iommu->reg + DMAR_VCCAP_REG);
>>> + if (!(cap & DMA_VCS_PAS)) {
>>> + pr_warn("IOMMU: %s: Emulation software doesn't
>>> support PASID allocation\n",
>>> + iommu->name);
>>> + return -ENODEV;
>>> + }
>>> +
>>> + raw_spin_lock_irqsave(&iommu->register_lock, flags);
>>> + dmar_writeq(iommu->reg + DMAR_VCMD_REG, VCMD_CMD_ALLOC);
>>> + IOMMU_WAIT_OP(iommu, DMAR_VCRSP_REG, dmar_readq,
>>> + !(res & VCMD_VRSP_IP), res);
>>> + raw_spin_unlock_irqrestore(&iommu->register_lock, flags);
>>> +
>>> + err_code = VCMD_VRSP_EC(res);
>>> + switch (err_code) {
>>> + case VCMD_VRSP_EC_SUCCESS:
>>> + *pasid = VCMD_VRSP_RESULE(res);
>>> + break;
>>> + case VCMD_VRSP_EC_UNAVAIL:
>>> + pr_info("IOMMU: %s: No PASID available\n",
>>> iommu->name);
>>> + ret = -ENOMEM;
>>> + break;
>>> + default:
>>> + ret = -ENODEV;
>>> + pr_warn("IOMMU: %s: Unkonwn error code %d\n",
>> unknown
>>> + iommu->name, err_code);
>>> + }
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +void vcmd_free_pasid(struct intel_iommu *iommu, unsigned int pasid)
>>> +{
>>> + u64 res;
>>> + u8 err_code;
>>> + unsigned long flags;
>> Shall we check as well the cap is set?
> yes, good point.
>
>>> +
>>> + raw_spin_lock_irqsave(&iommu->register_lock, flags);
>>> + dmar_writeq(iommu->reg + DMAR_VCMD_REG, (pasid << 8) |
>>> VCMD_CMD_FREE);
>>> + IOMMU_WAIT_OP(iommu, DMAR_VCRSP_REG, dmar_readq,
>>> + !(res & VCMD_VRSP_IP), res);
>>> + raw_spin_unlock_irqrestore(&iommu->register_lock, flags);
>>> +
>>> + err_code = VCMD_VRSP_EC(res);
>>> + switch (err_code) {
>>> + case VCMD_VRSP_EC_SUCCESS:
>>> + break;
>>> + case VCMD_VRSP_EC_INVAL:
>>> + pr_info("IOMMU: %s: Invalid PASID\n", iommu->name);
>>> + break;
>>> + default:
>>> + pr_warn("IOMMU: %s: Unkonwn error code %d\n",
>> unknown
>>> + iommu->name, err_code);
>>> + }
>>> +}
>>> +
>>> /*
>>> * Per device pasid table management:
>>> */
>>> diff --git a/drivers/iommu/intel-pasid.h
>>> b/drivers/iommu/intel-pasid.h index 23537b3..0999dfe 100644
>>> --- a/drivers/iommu/intel-pasid.h
>>> +++ b/drivers/iommu/intel-pasid.h
>>> @@ -19,6 +19,16 @@
>>> #define PASID_PDE_SHIFT 6
>>> #define MAX_NR_PASID_BITS 20
>>>
>>> +/* Virtual command interface for enlightened pasid management. */
>>> +#define VCMD_CMD_ALLOC 0x1
>>> +#define VCMD_CMD_FREE 0x2
>>> +#define VCMD_VRSP_IP 0x1
>>> +#define VCMD_VRSP_EC(e) (((e) >> 1) & 0x3)
>> s/EC/SC? for Status Code and below
> Good, that would match the spec.
>
>>> +#define VCMD_VRSP_EC_SUCCESS 0
>>> +#define VCMD_VRSP_EC_UNAVAIL 1
>> nit: _NO_VALID_PASID
> Other than SUCCESS, these codes are PASID command specific. I think it
> can be called _NO_PASID_AVAIL to match Spec. Fig 10-87 "No PASID
> Available"
yes that's what I meant actually ;-)
>
>>> +#define VCMD_VRSP_EC_INVAL 1
>> nit: _INVALID_PASID
> Agreed
>>> +#define VCMD_VRSP_RESULE(e) (((e) >> 8) & 0xfffff)
>> nit: s/RESULE/RSLT?
> yes. Also the mask bits should be 8 to 63
> s/0xfffff/GENMASK_ULL(63, 8))/
Well the macro definition looks correct as 63:28 is RsvdZ

Thanks

Eric
>
>>> +
>>> /*
>>> * Domain ID reserved for pasid entries programmed for first-level
>>> * only and pass-through transfer modes.
>>> @@ -69,5 +79,6 @@ int intel_pasid_setup_pass_through(struct
>>> intel_iommu *iommu, struct device *dev, int pasid);
>>> void intel_pasid_tear_down_entry(struct intel_iommu *iommu,
>>> struct device *dev, int pasid);
>>> -
>>> +int vcmd_alloc_pasid(struct intel_iommu *iommu, unsigned int
>>> *pasid); +void vcmd_free_pasid(struct intel_iommu *iommu, unsigned
>>> int pasid); #endif /* __INTEL_PASID_H */
>>> diff --git a/include/linux/intel-iommu.h
>>> b/include/linux/intel-iommu.h index 6925a18..bff907b 100644
>>> --- a/include/linux/intel-iommu.h
>>> +++ b/include/linux/intel-iommu.h
>>> @@ -173,6 +173,7 @@
>>> #define ecap_smpwc(e) (((e) >> 48) & 0x1)
>>> #define ecap_flts(e) (((e) >> 47) & 0x1)
>>> #define ecap_slts(e) (((e) >> 46) & 0x1)
>>> +#define ecap_vcs(e) (((e) >> 44) & 0x1)
>>> #define ecap_smts(e) (((e) >> 43) & 0x1)
>>> #define ecap_dit(e) ((e >> 41) & 0x1)
>>> #define ecap_pasid(e) ((e >> 40) & 0x1)
>>> @@ -289,6 +290,7 @@
>>>
>>> /* PRS_REG */
>>> #define DMA_PRS_PPR ((u32)1)
>>> +#define DMA_VCS_PAS ((u64)1)
>>>
>>> #define IOMMU_WAIT_OP(iommu, offset, op, cond,
>>> sts) \ do
>>> {
>>> \
>>
>> Thanks
>>
>> Eric
>>
>
> [Jacob Pan]
>