[PATCH RFC 10/19] iommu/amd: Add unmap_read_dirty() support

Joao Martins
2022-04-28T21:11:39Z

AMD implementation of unmap_read_dirty() is pretty simple as
mostly reuses unmap code with the extra addition of marshalling
the dirty bit into the bitmap as it walks the to-be-unmapped
IOPTE.

Extra care is taken though, to switch over to cmpxchg as opposed
to a non-serialized store to the PTE and testing the dirty bit
only set until cmpxchg succeeds to set to 0.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
drivers/iommu/amd/io_pgtable.c | 44 +++++++++++++++++++++++++++++-----
drivers/iommu/amd/iommu.c | 22 +++++++++++++++++
2 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/amd/io_pgtable.c b/drivers/iommu/amd/io_pgtable.c
index 8325ef193093..1868c3b58e6d 100644
--- a/drivers/iommu/amd/io_pgtable.c
+++ b/drivers/iommu/amd/io_pgtable.c
@@ -355,6 +355,16 @@ static void free_clear_pte(u64 *pte, u64 pteval, struct list_head *freelist)
free_sub_pt(pt, mode, freelist);
}

+static bool free_pte_dirty(u64 *pte, u64 pteval)
+{
+ bool dirty = false;
+
+ while (IOMMU_PTE_DIRTY(cmpxchg64(pte, pteval, 0)))
+ dirty = true;
+
+ return dirty;
+}
+
/*
* Generic mapping functions. It maps a physical address into a DMA
* address space. It allocates the page table pages if necessary.
@@ -428,10 +438,11 @@ static int iommu_v1_map_page(struct io_pgtable_ops *ops, unsigned long iova,
return ret;
}

-static unsigned long iommu_v1_unmap_page(struct io_pgtable_ops *ops,
- unsigned long iova,
- size_t size,
- struct iommu_iotlb_gather *gather)
+static unsigned long __iommu_v1_unmap_page(struct io_pgtable_ops *ops,
+ unsigned long iova,
+ size_t size,
+ struct iommu_iotlb_gather *gather,
+ struct iommu_dirty_bitmap *dirty)
{
struct amd_io_pgtable *pgtable = io_pgtable_ops_to_data(ops);
unsigned long long unmapped;
@@ -445,11 +456,15 @@ static unsigned long iommu_v1_unmap_page(struct io_pgtable_ops *ops,
while (unmapped < size) {
pte = fetch_pte(pgtable, iova, &unmap_size);
if (pte) {
- int i, count;
+ unsigned long i, count;
+ bool pte_dirty = false;

count = PAGE_SIZE_PTE_COUNT(unmap_size);
for (i = 0; i < count; i++)
- pte[i] = 0ULL;
+ pte_dirty |= free_pte_dirty(&pte[i], pte[i]);
+
+ if (unlikely(pte_dirty && dirty))
+ iommu_dirty_bitmap_record(dirty, iova, unmap_size);
}

iova = (iova & ~(unmap_size - 1)) + unmap_size;
@@ -461,6 +476,22 @@ static unsigned long iommu_v1_unmap_page(struct io_pgtable_ops *ops,
return unmapped;
}

+static unsigned long iommu_v1_unmap_page(struct io_pgtable_ops *ops,
+ unsigned long iova,
+ size_t size,
+ struct iommu_iotlb_gather *gather)
+{
+ return __iommu_v1_unmap_page(ops, iova, size, gather, NULL);
+}
+
+static unsigned long iommu_v1_unmap_page_read_dirty(struct io_pgtable_ops *ops,
+ unsigned long iova, size_t size,
+ struct iommu_iotlb_gather *gather,
+ struct iommu_dirty_bitmap *dirty)
+{
+ return __iommu_v1_unmap_page(ops, iova, size, gather, dirty);
+}
+
static phys_addr_t iommu_v1_iova_to_phys(struct io_pgtable_ops *ops, unsigned long iova)
{
struct amd_io_pgtable *pgtable = io_pgtable_ops_to_data(ops);
@@ -575,6 +606,7 @@ static struct io_pgtable *v1_alloc_pgtable(struct io_pgtable_cfg *cfg, void *coo
pgtable->iop.ops.unmap = iommu_v1_unmap_page;
pgtable->iop.ops.iova_to_phys = iommu_v1_iova_to_phys;
pgtable->iop.ops.read_and_clear_dirty = iommu_v1_read_and_clear_dirty;
+ pgtable->iop.ops.unmap_read_dirty = iommu_v1_unmap_page_read_dirty;

return &pgtable->iop;
}
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 0a86392b2367..a8fcb6e9a684 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2144,6 +2144,27 @@ static size_t amd_iommu_unmap(struct iommu_domain *dom, unsigned long iova,
return r;
}

+static size_t amd_iommu_unmap_read_dirty(struct iommu_domain *dom,
+ unsigned long iova, size_t page_size,
+ struct iommu_iotlb_gather *gather,
+ struct iommu_dirty_bitmap *dirty)
+{
+ struct protection_domain *domain = to_pdomain(dom);
+ struct io_pgtable_ops *ops = &domain->iop.iop.ops;
+ size_t r;
+
+ if ((amd_iommu_pgtable == AMD_IOMMU_V1) &&
+ (domain->iop.mode == PAGE_MODE_NONE))
+ return 0;
+
+ r = (ops->unmap_read_dirty) ?
+ ops->unmap_read_dirty(ops, iova, page_size, gather, dirty) : 0;
+
+ amd_iommu_iotlb_gather_add_page(dom, gather, iova, page_size);
+
+ return r;
+}
+
static phys_addr_t amd_iommu_iova_to_phys(struct iommu_domain *dom,
dma_addr_t iova)
{
@@ -2370,6 +2391,7 @@ const struct iommu_ops amd_iommu_ops = {
.free = amd_iommu_domain_free,
.set_dirty_tracking = amd_iommu_set_dirty_tracking,
.read_and_clear_dirty = amd_iommu_read_and_clear_dirty,
+ .unmap_read_dirty = amd_iommu_unmap_read_dirty,
}
};

--
2.17.2