Re: [PATCH v6 01/10] iommu/vt-d: Enlightened PASID allocation

[Jacob Pan <jacob.jun.pan@linux.intel.com>]

On Wed, 23 Oct 2019 09:53:04 +0800
Lu Baolu <baolu.lu@linux.intel.com> wrote:

> Hi Ashok,
> 
> Thanks for reviewing the patch.
> 
> On 10/23/19 8:45 AM, Raj, Ashok wrote:
> > On Tue, Oct 22, 2019 at 04:53:14PM -0700, 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. 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.  
> > 
> > The above paragraph seems a bit confusing, there is no reference
> > to caching mode for for VCMD... some suggestion below.
> > 
> > Enabling IOMMU in a guest requires communication with the host
> > driver for certain aspects. Use of PASID ID to enable Shared Virtual
> > Addressing (SVA) requires managing PASID's in the host. VT-d 3.0
> > spec provides a Virtual Command Register (VCMD) to facilitate this.
> > Writes to this register in the guest are trapped by Qemu and
> > proxies the call to the host driver....  
> 
> Yours is better. Will use it.
> 
I will roll that in to v7
> > 
> >   
> >>
> >> This patch adds the enlightened PASID allocation/free interfaces
> >> 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>
> >> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> >> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> >> ---
> >>   drivers/iommu/intel-pasid.c | 83
> >> +++++++++++++++++++++++++++++++++++++++++++++
> >> drivers/iommu/intel-pasid.h | 13 ++++++-
> >> include/linux/intel-iommu.h |  2 ++ 3 files changed, 97
> >> insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/iommu/intel-pasid.c
> >> b/drivers/iommu/intel-pasid.c index 040a445be300..76bcbb21e112
> >> 100644 --- a/drivers/iommu/intel-pasid.c
> >> +++ b/drivers/iommu/intel-pasid.c
> >> @@ -63,6 +63,89 @@ void *intel_pasid_lookup_id(int pasid)
> >>   	return p;
> >>   }
> >>   
> >> +static int check_vcmd_pasid(struct intel_iommu *iommu)
> >> +{
> >> +	u64 cap;
> >> +
> >> +	if (!ecap_vcs(iommu->ecap)) {
> >> +		pr_warn("IOMMU: %s: Hardware doesn't support
> >> virtual command\n",
> >> +			iommu->name);
> >> +		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;
> >> +	}
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +int vcmd_alloc_pasid(struct intel_iommu *iommu, unsigned int
> >> *pasid) +{
> >> +	u64 res;
> >> +	u8 status_code;
> >> +	unsigned long flags;
> >> +	int ret = 0;
> >> +
> >> +	ret = check_vcmd_pasid(iommu);  
> > 
> > Do you have to check this everytime? every dmar_readq is going to
> > trap to the other side ...  
> 
> Yes. We don't need to check it every time. Check once and save the
> result during boot is enough.
> 
> How about below incremental change?
> 
Below is good but I was thinking to include vccap in struct
intel_iommu{} where cap and ecaps reside. i.e.
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index 14b87ae2916a..e2cf25c9c956 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -528,6 +528,7 @@ struct intel_iommu {
        u64             reg_size; /* size of hw register set */
        u64             cap;
        u64             ecap;
+       u64             vccap;

Also, we can use a static branch here.

> diff --git a/drivers/iommu/intel-pasid.c b/drivers/iommu/intel-pasid.c
> index ff7e877b7a4d..c15d9d7e1e73 100644
> --- a/drivers/iommu/intel-pasid.c
> +++ b/drivers/iommu/intel-pasid.c
> @@ -29,22 +29,29 @@ u32 intel_pasid_max_id = PASID_MAX;
> 
>   static int check_vcmd_pasid(struct intel_iommu *iommu)
>   {
> +       static int vcmd_supported = -EINVAL;
>          u64 cap;
> 
> +       if (vcmd_supported != -EINVAL)
> +               return vcmd_supported;
> +
>          if (!ecap_vcs(iommu->ecap)) {
>                  pr_warn("IOMMU: %s: Hardware doesn't support virtual 
> command\n",
>                          iommu->name);
> -               return -ENODEV;
> +               vcmd_supported = -ENODEV;
> +               return vcmd_supported;
>          }
> 
>          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;
> +               vcmd_supported = -ENODEV;
> +               return vcmd_supported;
>          }
> 
> -       return 0;
> +       vcmd_supported = 0;
> +       return vcmd_supported;
>   }
> 
>   int vcmd_alloc_pasid(struct intel_iommu *iommu, unsigned int *pasid)
> 
> Best regards,
> baolu
> 
> >   
> >> +	if (ret)
> >> +		return ret;
> >> +
> >> +	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);
> >> +
> >> +	status_code = VCMD_VRSP_SC(res);
> >> +	switch (status_code) {
> >> +	case VCMD_VRSP_SC_SUCCESS:
> >> +		*pasid = VCMD_VRSP_RESULT(res);
> >> +		break;
> >> +	case VCMD_VRSP_SC_NO_PASID_AVAIL:
> >> +		pr_info("IOMMU: %s: No PASID available\n",
> >> iommu->name);
> >> +		ret = -ENOMEM;
> >> +		break;
> >> +	default:
> >> +		ret = -ENODEV;
> >> +		pr_warn("IOMMU: %s: Unexpected error code %d\n",
> >> +			iommu->name, status_code);
> >> +	}
> >> +
> >> +	return ret;
> >> +}
> >> +
> >> +void vcmd_free_pasid(struct intel_iommu *iommu, unsigned int
> >> pasid) +{
> >> +	u64 res;
> >> +	u8 status_code;
> >> +	unsigned long flags;
> >> +
> >> +	if (check_vcmd_pasid(iommu))
> >> +		return;
> >> +
> >> +	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);
> >> +
> >> +	status_code = VCMD_VRSP_SC(res);
> >> +	switch (status_code) {
> >> +	case VCMD_VRSP_SC_SUCCESS:
> >> +		break;
> >> +	case VCMD_VRSP_SC_INVALID_PASID:
> >> +		pr_info("IOMMU: %s: Invalid PASID\n",
> >> iommu->name);
> >> +		break;
> >> +	default:
> >> +		pr_warn("IOMMU: %s: Unexpected error code %d\n",
> >> +			iommu->name, status_code);
> >> +	}
> >> +}
> >> +
> >>   /*
> >>    * Per device pasid table management:
> >>    */
> >> diff --git a/drivers/iommu/intel-pasid.h
> >> b/drivers/iommu/intel-pasid.h index fc8cd8f17de1..e413e884e685
> >> 100644 --- a/drivers/iommu/intel-pasid.h
> >> +++ b/drivers/iommu/intel-pasid.h
> >> @@ -23,6 +23,16 @@
> >>   #define is_pasid_enabled(entry)		(((entry)->lo >>
> >> 3) & 0x1) #define get_pasid_dir_size(entry)	(1 <<
> >> ((((entry)->lo >> 9) & 0x7) + 7)) 
> >> +/* 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_SC(e)			(((e) >> 1) & 0x3)
> >> +#define VCMD_VRSP_SC_SUCCESS		0
> >> +#define VCMD_VRSP_SC_NO_PASID_AVAIL	1
> >> +#define VCMD_VRSP_SC_INVALID_PASID	1
> >> +#define VCMD_VRSP_RESULT(e)		(((e) >> 8) & 0xfffff)
> >> +
> >>   /*
> >>    * Domain ID reserved for pasid entries programmed for
> >> first-level
> >>    * only and pass-through transfer modes.
> >> @@ -95,5 +105,6 @@ 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 ed11ef594378..eea7468694a7
> >> 100644 --- a/include/linux/intel-iommu.h
> >> +++ b/include/linux/intel-iommu.h
> >> @@ -161,6 +161,7 @@
> >>   #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)
> >> @@ -279,6 +280,7 @@
> >>   
> >>   /* PRS_REG */
> >>   #define DMA_PRS_PPR	((u32)1)
> >> +#define DMA_VCS_PAS	((u64)1)
> >>   
> >>   #define IOMMU_WAIT_OP(iommu, offset, op, cond,
> >> sts)			\ do
> >> {
> >> \ -- 2.7.4
> >>  
> >   

[Jacob Pan]
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu