Re: [PATCH v7 04/11] iommu/vt-d: Replace Intel specific PASID allocator with IOASID

[Auger Eric]

Hi Jacob,

On 11/8/19 11:55 PM, Jacob Pan wrote:
> On Fri, 8 Nov 2019 12:30:31 +0100
> Auger Eric <eric.auger@xxxxxxxxxx> wrote:
> 
>> Hi Jacob,
>>
>> On 10/24/19 9:54 PM, Jacob Pan wrote:
>>> Make use of generic IOASID code to manage PASID allocation,
>>> free, and lookup. Replace Intel specific code.
>>>
>>> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
>>> ---
>>>  drivers/iommu/intel-iommu.c | 12 ++++++------
>>>  drivers/iommu/intel-pasid.c | 36
>>> ------------------------------------ drivers/iommu/intel-svm.c   |
>>> 39 +++++++++++++++++++++++---------------- 3 files changed, 29
>>> insertions(+), 58 deletions(-)
>>>
>>> diff --git a/drivers/iommu/intel-iommu.c
>>> b/drivers/iommu/intel-iommu.c index ced1d89ef977..2ea09b988a23
>>> 100644 --- a/drivers/iommu/intel-iommu.c
>>> +++ b/drivers/iommu/intel-iommu.c
>>> @@ -5311,7 +5311,7 @@ static void auxiliary_unlink_device(struct
>>> dmar_domain *domain, domain->auxd_refcnt--;
>>>  
>>>  	if (!domain->auxd_refcnt && domain->default_pasid > 0)
>>> -		intel_pasid_free_id(domain->default_pasid);
>>> +		ioasid_free(domain->default_pasid);
>>>  }
>>>  
>>>  static int aux_domain_add_dev(struct dmar_domain *domain,
>>> @@ -5329,10 +5329,10 @@ static int aux_domain_add_dev(struct
>>> dmar_domain *domain, if (domain->default_pasid <= 0) {
>>>  		int pasid;
>>>  
>>> -		pasid = intel_pasid_alloc_id(domain, PASID_MIN,
>>> -
>>> pci_max_pasids(to_pci_dev(dev)),
>>> -					     GFP_KERNEL);
>>> -		if (pasid <= 0) {
>>> +		/* No private data needed for the default pasid */
>>> +		pasid = ioasid_alloc(NULL, PASID_MIN,
>>> pci_max_pasids(to_pci_dev(dev)) - 1,
>>> +				NULL);
>>> +		if (pasid == INVALID_IOASID) {
>>>  			pr_err("Can't allocate default pasid\n");
>>>  			return -ENODEV;
>>>  		}
>>> @@ -5368,7 +5368,7 @@ static int aux_domain_add_dev(struct
>>> dmar_domain *domain, spin_unlock(&iommu->lock);
>>>  	spin_unlock_irqrestore(&device_domain_lock, flags);
>>>  	if (!domain->auxd_refcnt && domain->default_pasid > 0)
>>> -		intel_pasid_free_id(domain->default_pasid);
>>> +		ioasid_free(domain->default_pasid);
>>>  
>>>  	return ret;
>>>  }
>>> diff --git a/drivers/iommu/intel-pasid.c
>>> b/drivers/iommu/intel-pasid.c index d81e857d2b25..e79d680fe300
>>> 100644 --- a/drivers/iommu/intel-pasid.c
>>> +++ b/drivers/iommu/intel-pasid.c
>>> @@ -26,42 +26,6 @@
>>>   */
>>>  static DEFINE_SPINLOCK(pasid_lock);
>>>  u32 intel_pasid_max_id = PASID_MAX;
>>> -static DEFINE_IDR(pasid_idr);
>>> -
>>> -int intel_pasid_alloc_id(void *ptr, int start, int end, gfp_t gfp)
>>> -{
>>> -	int ret, min, max;
>>> -
>>> -	min = max_t(int, start, PASID_MIN);
>>> -	max = min_t(int, end, intel_pasid_max_id);
>>> -
>>> -	WARN_ON(in_interrupt());
>>> -	idr_preload(gfp);
>>> -	spin_lock(&pasid_lock);
>>> -	ret = idr_alloc(&pasid_idr, ptr, min, max, GFP_ATOMIC);
>>> -	spin_unlock(&pasid_lock);
>>> -	idr_preload_end();
>>> -
>>> -	return ret;
>>> -}
>>> -
>>> -void intel_pasid_free_id(int pasid)
>>> -{
>>> -	spin_lock(&pasid_lock);
>>> -	idr_remove(&pasid_idr, pasid);
>>> -	spin_unlock(&pasid_lock);
>>> -}
>>> -
>>> -void *intel_pasid_lookup_id(int pasid)
>>> -{
>>> -	void *p;
>>> -
>>> -	spin_lock(&pasid_lock);
>>> -	p = idr_find(&pasid_idr, pasid);
>>> -	spin_unlock(&pasid_lock);
>>> -
>>> -	return p;
>>> -}
>>>  
>>>  int vcmd_alloc_pasid(struct intel_iommu *iommu, unsigned int
>>> *pasid) {
>>> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
>>> index 9b159132405d..a9a7f85a09bc 100644
>>> --- a/drivers/iommu/intel-svm.c
>>> +++ b/drivers/iommu/intel-svm.c
>>> @@ -17,6 +17,7 @@
>>>  #include <linux/dmar.h>
>>>  #include <linux/interrupt.h>
>>>  #include <linux/mm_types.h>
>>> +#include <linux/ioasid.h>
>>>  #include <asm/page.h>
>>>  
>>>  #include "intel-pasid.h"
>>> @@ -318,16 +319,15 @@ int intel_svm_bind_mm(struct device *dev, int
>>> *pasid, int flags, struct svm_dev_ if (pasid_max >
>>> intel_pasid_max_id) pasid_max = intel_pasid_max_id;
>>>  
>>> -		/* Do not use PASID 0 in caching mode (virtualised
>>> IOMMU) */
>>> -		ret = intel_pasid_alloc_id(svm,
>>> -					   !!cap_caching_mode(iommu->cap),
>>> -					   pasid_max - 1,
>>> GFP_KERNEL);
>>> -		if (ret < 0) {
>>> +		/* Do not use PASID 0, reserved for RID to PASID */
>>> +		svm->pasid = ioasid_alloc(NULL, PASID_MIN,
>>> +					pasid_max - 1, svm);  
>> pasid_max -1 is inclusive. whereas max param in intel_pasid_alloc_id()
>> is exclusive right? If you fixed an issue, you can mention it in the
>> commit message.
> yes, i should mention that. intel_pasid_alloc_id() uses IDR which is
> end exclusive. ioasid uses xarray, which is inclusive. 
>>> +		if (svm->pasid == INVALID_IOASID) {  
>>>  			kfree(svm);>
>>> kfree(sdev);  
>>> +			ret = ENOSPC;  
>> -ENOSPC.
>> Nit: in 2/11 vcmd_alloc_pasid returned -ENOMEM
> yes, it should be -ENOSPC as well.
> 
>>>  			goto out;
>>>  		}
>>> -		svm->pasid = ret;
>>>  		svm->notifier.ops = &intel_mmuops;
>>>  		svm->mm = mm;
>>>  		svm->flags = flags;
>>> @@ -337,7 +337,7 @@ int intel_svm_bind_mm(struct device *dev, int
>>> *pasid, int flags, struct svm_dev_ if (mm) {
>>>  			ret =
>>> mmu_notifier_register(&svm->notifier, mm); if (ret) {
>>> -				intel_pasid_free_id(svm->pasid);
>>> +				ioasid_free(svm->pasid);
>>>  				kfree(svm);
>>>  				kfree(sdev);
>>>  				goto out;
>>> @@ -353,7 +353,7 @@ int intel_svm_bind_mm(struct device *dev, int
>>> *pasid, int flags, struct svm_dev_ if (ret) {
>>>  			if (mm)
>>>  				mmu_notifier_unregister(&svm->notifier,
>>> mm);
>>> -			intel_pasid_free_id(svm->pasid);
>>> +			ioasid_free(svm->pasid);
>>>  			kfree(svm);
>>>  			kfree(sdev);
>>>  			goto out;
>>> @@ -401,7 +401,12 @@ int intel_svm_unbind_mm(struct device *dev,
>>> int pasid) if (!iommu)
>>>  		goto out;
>>>  
>>> -	svm = intel_pasid_lookup_id(pasid);
>>> +	svm = ioasid_find(NULL, pasid, NULL);
>>> +	if (IS_ERR(svm)) {
>>> +		ret = PTR_ERR(svm);
>>> +		goto out;
>>> +	}
>>> +
>>>  	if (!svm)
>>>  		goto out;
>>>  
>>> @@ -423,7 +428,9 @@ int intel_svm_unbind_mm(struct device *dev, int
>>> pasid) kfree_rcu(sdev, rcu);
>>>  
>>>  				if (list_empty(&svm->devs)) {
>>> -
>>> intel_pasid_free_id(svm->pasid);
>>> +					/* Clear private data so
>>> that free pass check */> +
>>> ioasid_set_data(svm->pasid, NULL);  
>> I don't get the above comment. Why is it needed?
> Having private data associated with an IOASID is an indicator that this
> IOASID is busy. So we have to clear it to signal it is free.
> Actually, I am planning to introduce a refcount per IOASID since there
> will be multiple users of IOASID, e.g. IOMMU driver and KVM. When
> refcount == 0, we can free.
Ah OK I missed that. This is a specificity of the intel custom PASID
allocator, ie intel_ioasid_free and not a generic behavior.

Thanks

Eric
> 
>>> +					ioasid_free(svm->pasid);
>>>  					if (svm->mm)
>>>  						mmu_notifier_unregister(&svm->notifier,
>>> svm->mm); 
>>> @@ -458,10 +465,11 @@ int intel_svm_is_pasid_valid(struct device
>>> *dev, int pasid) if (!iommu)
>>>  		goto out;
>>>  
>>> -	svm = intel_pasid_lookup_id(pasid);
>>> -	if (!svm)
>>> +	svm = ioasid_find(NULL, pasid, NULL);
>>> +	if (IS_ERR(svm)) {
>>> +		ret = PTR_ERR(svm);
>>>  		goto out;
>>> -
>>> +	}
>>>  	/* init_mm is used in this case */
>>>  	if (!svm->mm)
>>>  		ret = 1;
>>> @@ -568,13 +576,12 @@ static irqreturn_t prq_event_thread(int irq,
>>> void *d) 
>>>  		if (!svm || svm->pasid != req->pasid) {
>>>  			rcu_read_lock();
>>> -			svm = intel_pasid_lookup_id(req->pasid);
>>> +			svm = ioasid_find(NULL, req->pasid, NULL);
>>>  			/* It *can't* go away, because the driver
>>> is not permitted
>>>  			 * to unbind the mm while any page faults
>>> are outstanding.
>>>  			 * So we only need RCU to protect the
>>> internal idr code. */ rcu_read_unlock();
>>> -
>>> -			if (!svm) {
>>> +			if (IS_ERR(svm) || !svm) {
>>>  				pr_err("%s: Page request for
>>> invalid PASID %d: %08llx %08llx\n", iommu->name, req->pasid,
>>> ((unsigned long long *)req)[0], ((unsigned long long *)req)[1]);
>>>   
>> Thanks
>>
>> Eric
>>
> 
> [Jacob Pan]
>