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From:   Tom Murphy <tmurphy@arista.com>
Date:   Wed, 15 May 2019 13:46:43 +0100
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Subject: Re: [PATCH v3 2/4] iommu/dma-iommu: Handle deferred devices
To:     Christoph Hellwig <hch@infradead.org>
Cc:     iommu@lists.linux-foundation.org, Tom Murphy <murphyt7@tcd.ie>,
        Joerg Roedel <joro@8bytes.org>,
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like this?

In that case we need to add a call to iommu_dma_alloc_remap.

From 862aeebb601008cf863e3aff4ff8ed7cefebeefa Mon Sep 17 00:00:00 2001
From: Tom Murphy <tmurphy@tmurphy-419tom-0.sjc.aristanetworks.com>
Date: Wed, 15 May 2019 05:43:25 -0700
Subject: [PATCH] iommu/dma-iommu: Handle deferred devices

Handle devices which defer their attach to the iommu in the dma-iommu api

Signed-off-by: Tom Murphy <tmurphy@arista.com>
---
 drivers/iommu/dma-iommu.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 7f313cfa9..a48ae906d 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -22,6 +22,7 @@
 #include <linux/pci.h>
 #include <linux/scatterlist.h>
 #include <linux/vmalloc.h>
+#include <linux/crash_dump.h>

 struct iommu_dma_msi_page {
     struct list_head    list;
@@ -323,6 +324,21 @@ static int iommu_dma_init_domain(struct
iommu_domain *domain, dma_addr_t base,
     return iova_reserve_iommu_regions(dev, domain);
 }

+static int handle_deferred_device(struct device *dev,
+        struct iommu_domain *domain)
+{
+    const struct iommu_ops *ops = domain->ops;
+
+    if (!is_kdump_kernel())
+        return 0;
+
+    if (unlikely(ops->is_attach_deferred &&
+            ops->is_attach_deferred(domain, dev)))
+        return iommu_attach_device(domain, dev);
+
+    return 0;
+}
+
 /**
  * dma_info_to_prot - Translate DMA API directions and attributes to IOMMU API
  *                    page flags.
@@ -432,6 +448,9 @@ static dma_addr_t __iommu_dma_map(struct device
*dev, phys_addr_t phys,
     size_t iova_off = 0;
     dma_addr_t iova;

+    if (unlikely(handle_deferred_device(dev, domain)))
+        return DMA_MAPPING_ERROR;
+
     if (cookie->type == IOMMU_DMA_IOVA_COOKIE) {
         iova_off = iova_offset(&cookie->iovad, phys);
         size = iova_align(&cookie->iovad, size + iova_off);
@@ -609,6 +628,9 @@ static void *iommu_dma_alloc_remap(struct device
*dev, size_t size,
     dma_addr_t iova;
     void *vaddr;

+    if (unlikely(handle_deferred_device(dev, domain)))
+        return DMA_MAPPING_ERROR;
+
     *dma_handle = DMA_MAPPING_ERROR;

     min_size = alloc_sizes & -alloc_sizes;
@@ -836,7 +858,7 @@ static dma_addr_t iommu_dma_map_page(struct device
*dev, struct page *page,
     bool coherent = dev_is_dma_coherent(dev);
     dma_addr_t dma_handle;

-    dma_handle =__iommu_dma_map(dev, phys, size,
+    dma_handle = __iommu_dma_map(dev, phys, size,
             dma_info_to_prot(dir, coherent, attrs),
             iommu_get_dma_domain(dev));
     if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
@@ -954,6 +976,9 @@ static int iommu_dma_map_sg(struct device *dev,
struct scatterlist *sg,
     unsigned long mask = dma_get_seg_boundary(dev);
     int i;

+    if (unlikely(handle_deferred_device(dev, domain)))
+        return 0;
+
     if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
         iommu_dma_sync_sg_for_device(dev, sg, nents, dir);

-- 
2.20.0

On Tue, May 7, 2019 at 7:40 AM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Mon, May 06, 2019 at 07:52:04PM +0100, Tom Murphy wrote:
> > +static int handle_deferred_device(struct device *dev)
> > +{
> > +     struct iommu_domain *domain;
> > +     const struct iommu_ops *ops;
> > +
> > +     if (!is_kdump_kernel())
> > +             return 0;
> > +
> > +     domain = iommu_get_domain_for_dev(dev);
>
> > -     dma_handle =__iommu_dma_map(dev, phys, size,
> > +     if (unlikely(handle_deferred_device(dev)))
> > +             return DMA_MAPPING_ERROR;
> > +
> > +     dma_handle = __iommu_dma_map(dev, phys, size,
>
> __iommu_dma_map already looks up the domain, and as far as I can
> tell all callers need the handle_deferred_device call.  Should we
> just move it to there and pass the domain from the caller?
>
> Also shouldn't the iommu_attach_device call inside
> handle_deferred_device also get an unlikely marker?