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

[Jacob Pan]

On Wed, 24 Apr 2019 19:27:52 +0200
Auger Eric <eric.auger@xxxxxxxxxx> wrote:

> Hi Jacob,
> 
> On 4/24/19 1:31 AM, Jacob Pan wrote:
> > From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > 
> > 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@xxxxxxxxx>
> > Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > ---
> >  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 :).

> > +		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"

> > +#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))/

> > +
> >  /*
> >   * 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]