Re: [PATCH v1 3/3] iommu/amd: Optimize the IOMMU queue flush

[Jan Vesely <jan.vesely-kgbqMDwikbSVc3sceRu5cw@public.gmane.org>]

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On Tue, 2017-06-06 at 10:02 +0000, Nath, Arindam wrote:
> > -----Original Message-----
> > From: Lendacky, Thomas
> > Sent: Tuesday, June 06, 2017 1:23 AM
> > To: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> > Cc: Nath, Arindam <Arindam.Nath-5C7GfCeVMHo@public.gmane.org>; Joerg Roedel
> > <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>; Duran, Leo <leo.duran-5C7GfCeVMHo@public.gmane.org>; Suthikulpanit,
> > Suravee <Suravee.Suthikulpanit-5C7GfCeVMHo@public.gmane.org>
> > Subject: [PATCH v1 3/3] iommu/amd: Optimize the IOMMU queue flush
> > 
> > After reducing the amount of MMIO performed by the IOMMU during
> > operation,
> > perf data shows that flushing the TLB for all protection domains during
> > DMA unmapping is a performance issue. It is not necessary to flush the
> > TLBs for all protection domains, only the protection domains associated
> > with iova's on the flush queue.
> > 
> > Create a separate queue that tracks the protection domains associated with
> > the iova's on the flush queue. This new queue optimizes the flushing of
> > TLBs to the required protection domains.
> > 
> > Reviewed-by: Arindam Nath <arindam.nath-5C7GfCeVMHo@public.gmane.org>
> > Signed-off-by: Tom Lendacky <thomas.lendacky-5C7GfCeVMHo@public.gmane.org>
> > ---
> > drivers/iommu/amd_iommu.c |   56
> > ++++++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 50 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> > index 856103b..a5e77f0 100644
> > --- a/drivers/iommu/amd_iommu.c
> > +++ b/drivers/iommu/amd_iommu.c
> > @@ -103,7 +103,18 @@ struct flush_queue {
> > 	struct flush_queue_entry *entries;
> > };
> > 
> > +struct flush_pd_queue_entry {
> > +	struct protection_domain *pd;
> > +};
> > +
> > +struct flush_pd_queue {
> > +	/* No lock needed, protected by flush_queue lock */
> > +	unsigned next;
> > +	struct flush_pd_queue_entry *entries;
> > +};
> > +
> > static DEFINE_PER_CPU(struct flush_queue, flush_queue);
> > +static DEFINE_PER_CPU(struct flush_pd_queue, flush_pd_queue);
> > 
> > static atomic_t queue_timer_on;
> > static struct timer_list queue_timer;
> > @@ -2227,16 +2238,20 @@ static struct iommu_group
> > *amd_iommu_device_group(struct device *dev)
> >  *
> > 
> > ***********************************************************
> > ******************/
> > 
> > -static void __queue_flush(struct flush_queue *queue)
> > +static void __queue_flush(struct flush_queue *queue,
> > +			  struct flush_pd_queue *pd_queue)
> > {
> > -	struct protection_domain *domain;
> > 	unsigned long flags;
> > 	int idx;
> > 
> > 	/* First flush TLB of all known domains */
> > 	spin_lock_irqsave(&amd_iommu_pd_lock, flags);
> > -	list_for_each_entry(domain, &amd_iommu_pd_list, list)
> > -		domain_flush_tlb(domain);
> > +	for (idx = 0; idx < pd_queue->next; ++idx) {
> > +		struct flush_pd_queue_entry *entry;
> > +
> > +		entry = pd_queue->entries + idx;
> > +		domain_flush_tlb(entry->pd);
> > +	}
> > 	spin_unlock_irqrestore(&amd_iommu_pd_lock, flags);
> > 
> > 	/* Wait until flushes have completed */
> > @@ -2255,6 +2270,7 @@ static void __queue_flush(struct flush_queue
> > *queue)
> > 		entry->dma_dom = NULL;
> > 	}
> > 
> > +	pd_queue->next = 0;
> > 	queue->next = 0;
> > }
> > 
> > @@ -2263,13 +2279,15 @@ static void queue_flush_all(void)
> > 	int cpu;
> > 
> > 	for_each_possible_cpu(cpu) {
> > +		struct flush_pd_queue *pd_queue;
> > 		struct flush_queue *queue;
> > 		unsigned long flags;
> > 
> > 		queue = per_cpu_ptr(&flush_queue, cpu);
> > +		pd_queue = per_cpu_ptr(&flush_pd_queue, cpu);
> > 		spin_lock_irqsave(&queue->lock, flags);
> > 		if (queue->next > 0)
> > -			__queue_flush(queue);
> > +			__queue_flush(queue, pd_queue);
> > 		spin_unlock_irqrestore(&queue->lock, flags);
> > 	}
> > }
> > @@ -2283,6 +2301,8 @@ static void queue_flush_timeout(unsigned long
> > unsused)
> > static void queue_add(struct dma_ops_domain *dma_dom,
> > 		      unsigned long address, unsigned long pages)
> > {
> > +	struct flush_pd_queue_entry *pd_entry;
> > +	struct flush_pd_queue *pd_queue;
> > 	struct flush_queue_entry *entry;
> > 	struct flush_queue *queue;
> > 	unsigned long flags;
> > @@ -2292,10 +2312,22 @@ static void queue_add(struct dma_ops_domain
> > *dma_dom,
> > 	address >>= PAGE_SHIFT;
> > 
> > 	queue = get_cpu_ptr(&flush_queue);
> > +	pd_queue = get_cpu_ptr(&flush_pd_queue);
> > 	spin_lock_irqsave(&queue->lock, flags);
> > 
> > 	if (queue->next == FLUSH_QUEUE_SIZE)
> > -		__queue_flush(queue);
> > +		__queue_flush(queue, pd_queue);
> > +
> > +	for (idx = 0; idx < pd_queue->next; ++idx) {
> > +		pd_entry = pd_queue->entries + idx;
> > +		if (pd_entry->pd == &dma_dom->domain)
> > +			break;
> > +	}
> > +	if (idx == pd_queue->next) {
> > +		/* New protection domain, add it to the list */
> > +		pd_entry = pd_queue->entries + pd_queue->next++;
> > +		pd_entry->pd = &dma_dom->domain;
> > +	}
> > 
> > 	idx   = queue->next++;
> > 	entry = queue->entries + idx;
> > @@ -2309,6 +2341,7 @@ static void queue_add(struct dma_ops_domain
> > *dma_dom,
> > 	if (atomic_cmpxchg(&queue_timer_on, 0, 1) == 0)
> > 		mod_timer(&queue_timer, jiffies + msecs_to_jiffies(10));
> > 
> > +	put_cpu_ptr(&flush_pd_queue);
> > 	put_cpu_ptr(&flush_queue);
> > }
> > 
> > @@ -2810,6 +2843,8 @@ int __init amd_iommu_init_api(void)
> > 		return ret;
> > 
> > 	for_each_possible_cpu(cpu) {
> > +		struct flush_pd_queue *pd_queue =
> > per_cpu_ptr(&flush_pd_queue,
> > +							      cpu);
> > 		struct flush_queue *queue = per_cpu_ptr(&flush_queue,
> > cpu);
> > 
> > 		queue->entries = kzalloc(FLUSH_QUEUE_SIZE *
> > @@ -2819,6 +2854,12 @@ int __init amd_iommu_init_api(void)
> > 			goto out_put_iova;
> > 
> > 		spin_lock_init(&queue->lock);
> > +
> > +		pd_queue->entries = kzalloc(FLUSH_QUEUE_SIZE *
> > +					    sizeof(*pd_queue->entries),
> > +					    GFP_KERNEL);
> > +		if (!pd_queue->entries)
> > +			goto out_put_iova;
> > 	}
> > 
> > 	err = bus_set_iommu(&pci_bus_type, &amd_iommu_ops);
> > @@ -2836,9 +2877,12 @@ int __init amd_iommu_init_api(void)
> > 
> > out_put_iova:
> > 	for_each_possible_cpu(cpu) {
> > +		struct flush_pd_queue *pd_queue =
> > per_cpu_ptr(&flush_pd_queue,
> > +							      cpu);
> > 		struct flush_queue *queue = per_cpu_ptr(&flush_queue,
> > cpu);
> > 
> > 		kfree(queue->entries);
> > +		kfree(pd_queue->entries);
> > 	}
> > 
> > 	return -ENOMEM;
> 
> Craig and Jan, can you please confirm whether this patch fixes the
> IOMMU timeout errors you encountered before? If it does, then this is
> a better implementation of the fix I provided few weeks back.

I have only remote access to the machine, so I won't be able to test
until June 22nd.

Jan

> 
> Thanks,
> Arindam

-- 
Jan Vesely <jan.vesely-kgbqMDwikbSVc3sceRu5cw@public.gmane.org>

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