vfio/pds: Only use a single SGL for both seq and ack

Since the seq/ack operations never happen in parallel there
is no need for multiple scatter gather lists per region.
The current implementation is wasting memory. Fix this by
only using a single scatter-gather list for both the seq
and ack operations.

Signed-off-by: Brett Creeley <brett.creeley@amd.com>
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Link: https://lore.kernel.org/r/20231117001207.2793-3-brett.creeley@amd.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/pci/pds/dirty.c b/drivers/vfio/pci/pds/dirty.c
index 27607d7..4462f6e 100644 (file)
--- a/drivers/vfio/pci/pds/dirty.c
+++ b/drivers/vfio/pci/pds/dirty.c
@@ -100,35 +100,35 @@ static void pds_vfio_dirty_free_bitmaps(struct pds_vfio_dirty *dirty)
 }
 
 static void __pds_vfio_dirty_free_sgl(struct pds_vfio_pci_device *pds_vfio,
-                                     struct pds_vfio_bmp_info *bmp_info)
+                                     struct pds_vfio_dirty *dirty)
 {
        struct pci_dev *pdev = pds_vfio->vfio_coredev.pdev;
        struct device *pdsc_dev = &pci_physfn(pdev)->dev;
 
-       dma_unmap_single(pdsc_dev, bmp_info->sgl_addr,
-                        bmp_info->num_sge * sizeof(struct pds_lm_sg_elem),
+       dma_unmap_single(pdsc_dev, dirty->sgl_addr,
+                        dirty->num_sge * sizeof(struct pds_lm_sg_elem),
                         DMA_BIDIRECTIONAL);
-       kfree(bmp_info->sgl);
+       kfree(dirty->sgl);
 
-       bmp_info->num_sge = 0;
-       bmp_info->sgl = NULL;
-       bmp_info->sgl_addr = 0;
+       dirty->num_sge = 0;
+       dirty->sgl = NULL;
+       dirty->sgl_addr = 0;
 }
 
 static void pds_vfio_dirty_free_sgl(struct pds_vfio_pci_device *pds_vfio)
 {
-       if (pds_vfio->dirty.host_seq.sgl)
-               __pds_vfio_dirty_free_sgl(pds_vfio, &pds_vfio->dirty.host_seq);
-       if (pds_vfio->dirty.host_ack.sgl)
-               __pds_vfio_dirty_free_sgl(pds_vfio, &pds_vfio->dirty.host_ack);
+       struct pds_vfio_dirty *dirty = &pds_vfio->dirty;
+
+       if (dirty->sgl)
+               __pds_vfio_dirty_free_sgl(pds_vfio, dirty);
 }
 
-static int __pds_vfio_dirty_alloc_sgl(struct pds_vfio_pci_device *pds_vfio,
-                                     struct pds_vfio_bmp_info *bmp_info,
-                                     u32 page_count)
+static int pds_vfio_dirty_alloc_sgl(struct pds_vfio_pci_device *pds_vfio,
+                                   u32 page_count)
 {
        struct pci_dev *pdev = pds_vfio->vfio_coredev.pdev;
        struct device *pdsc_dev = &pci_physfn(pdev)->dev;
+       struct pds_vfio_dirty *dirty = &pds_vfio->dirty;
        struct pds_lm_sg_elem *sgl;
        dma_addr_t sgl_addr;
        size_t sgl_size;
@@ -147,30 +147,9 @@ static int __pds_vfio_dirty_alloc_sgl(struct pds_vfio_pci_device *pds_vfio,
                return -EIO;
        }
 
-       bmp_info->sgl = sgl;
-       bmp_info->num_sge = max_sge;
-       bmp_info->sgl_addr = sgl_addr;
-
-       return 0;
-}
-
-static int pds_vfio_dirty_alloc_sgl(struct pds_vfio_pci_device *pds_vfio,
-                                   u32 page_count)
-{
-       struct pds_vfio_dirty *dirty = &pds_vfio->dirty;
-       int err;
-
-       err = __pds_vfio_dirty_alloc_sgl(pds_vfio, &dirty->host_seq,
-                                        page_count);
-       if (err)
-               return err;
-
-       err = __pds_vfio_dirty_alloc_sgl(pds_vfio, &dirty->host_ack,
-                                        page_count);
-       if (err) {
-               __pds_vfio_dirty_free_sgl(pds_vfio, &dirty->host_seq);
-               return err;
-       }
+       dirty->sgl = sgl;
+       dirty->num_sge = max_sge;
+       dirty->sgl_addr = sgl_addr;
 
        return 0;
 }
@@ -328,6 +307,8 @@ static int pds_vfio_dirty_seq_ack(struct pds_vfio_pci_device *pds_vfio,
        u8 dma_dir = read_seq ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
        struct pci_dev *pdev = pds_vfio->vfio_coredev.pdev;
        struct device *pdsc_dev = &pci_physfn(pdev)->dev;
+       struct pds_vfio_dirty *dirty = &pds_vfio->dirty;
+       struct pds_lm_sg_elem *sgl;
        unsigned long long npages;
        struct sg_table sg_table;
        struct scatterlist *sg;
@@ -374,8 +355,9 @@ static int pds_vfio_dirty_seq_ack(struct pds_vfio_pci_device *pds_vfio,
        if (err)
                goto out_free_sg_table;
 
+       sgl = pds_vfio->dirty.sgl;
        for_each_sgtable_dma_sg(&sg_table, sg, i) {
-               struct pds_lm_sg_elem *sg_elem = &bmp_info->sgl[i];
+               struct pds_lm_sg_elem *sg_elem = &sgl[i];
 
                sg_elem->addr = cpu_to_le64(sg_dma_address(sg));
                sg_elem->len = cpu_to_le32(sg_dma_len(sg));
@@ -383,15 +365,15 @@ static int pds_vfio_dirty_seq_ack(struct pds_vfio_pci_device *pds_vfio,
 
        num_sge = sg_table.nents;
        size = num_sge * sizeof(struct pds_lm_sg_elem);
-       dma_sync_single_for_device(pdsc_dev, bmp_info->sgl_addr, size, dma_dir);
-       err = pds_vfio_dirty_seq_ack_cmd(pds_vfio, bmp_info->sgl_addr, num_sge,
+       dma_sync_single_for_device(pdsc_dev, dirty->sgl_addr, size, dma_dir);
+       err = pds_vfio_dirty_seq_ack_cmd(pds_vfio, dirty->sgl_addr, num_sge,
                                         offset, bmp_bytes, read_seq);
        if (err)
                dev_err(&pdev->dev,
                        "Dirty bitmap %s failed offset %u bmp_bytes %u num_sge %u DMA 0x%llx: %pe\n",
                        bmp_type_str, offset, bmp_bytes,
-                       num_sge, bmp_info->sgl_addr, ERR_PTR(err));
-       dma_sync_single_for_cpu(pdsc_dev, bmp_info->sgl_addr, size, dma_dir);
+                       num_sge, dirty->sgl_addr, ERR_PTR(err));
+       dma_sync_single_for_cpu(pdsc_dev, dirty->sgl_addr, size, dma_dir);
 
        dma_unmap_sgtable(pdsc_dev, &sg_table, dma_dir, 0);
 out_free_sg_table:

diff --git a/drivers/vfio/pci/pds/dirty.h b/drivers/vfio/pci/pds/dirty.h
index f78da25..9de5aac 100644 (file)
--- a/drivers/vfio/pci/pds/dirty.h
+++ b/drivers/vfio/pci/pds/dirty.h
@@ -7,9 +7,6 @@
 struct pds_vfio_bmp_info {
        unsigned long *bmp;
        u32 bmp_bytes;
-       struct pds_lm_sg_elem *sgl;
-       dma_addr_t sgl_addr;
-       u16 num_sge;
 };
 
 struct pds_vfio_dirty {
@@ -18,6 +15,9 @@ struct pds_vfio_dirty {
        u64 region_size;
        u64 region_start;
        u64 region_page_size;
+       struct pds_lm_sg_elem *sgl;
+       dma_addr_t sgl_addr;
+       u16 num_sge;
        bool is_enabled;
 };