Re: [PATCH v3 3/5] vduse: Support using userspace pages as bounce buffer

From: Jason Wang
Date: Wed Jul 20 2022 - 02:04:09 EST

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In reply to: Xie Yongji: "[PATCH v3 3/5] vduse: Support using userspace pages as bounce buffer"
Next in thread: Xie Yongji: "[PATCH v3 4/5] vduse: Support registering userspace memory for IOVA regions"
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On Wed, Jul 20, 2022 at 12:42 PM Xie Yongji <xieyongji@xxxxxxxxxxxxx> wrote:
>
> Introduce two APIs: vduse_domain_add_user_bounce_pages()
> and vduse_domain_remove_user_bounce_pages() to support
> adding and removing userspace pages for bounce buffers.
> During adding and removing, the DMA data would be copied
> from the kernel bounce pages to the userspace bounce pages
> and back.
>
> Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>

Acked-by: Jason Wang <jasowang@xxxxxxxxxx>

> ---
> drivers/vdpa/vdpa_user/iova_domain.c | 96 +++++++++++++++++++++++++---
> drivers/vdpa/vdpa_user/iova_domain.h | 8 +++
> 2 files changed, 96 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/iova_domain.c b/drivers/vdpa/vdpa_user/iova_domain.c
> index 50d7c08d5450..e682bc7ee6c9 100644
> --- a/drivers/vdpa/vdpa_user/iova_domain.c
> +++ b/drivers/vdpa/vdpa_user/iova_domain.c
> @@ -178,8 +178,9 @@ static void vduse_domain_bounce(struct vduse_iova_domain *domain,
> map->orig_phys == INVALID_PHYS_ADDR))
> return;
>
> - addr = page_address(map->bounce_page) + offset;
> - do_bounce(map->orig_phys + offset, addr, sz, dir);
> + addr = kmap_local_page(map->bounce_page);
> + do_bounce(map->orig_phys + offset, addr + offset, sz, dir);
> + kunmap_local(addr);
> size -= sz;
> iova += sz;
> }
> @@ -210,20 +211,23 @@ static struct page *
> vduse_domain_get_bounce_page(struct vduse_iova_domain *domain, u64 iova)
> {
> struct vduse_bounce_map *map;
> - struct page *page;
> + struct page *page = NULL;
>
> + read_lock(&domain->bounce_lock);
> map = &domain->bounce_maps[iova >> PAGE_SHIFT];
> - if (!map->bounce_page)
> - return NULL;
> + if (domain->user_bounce_pages || !map->bounce_page)
> + goto out;
>
> page = map->bounce_page;
> get_page(page);
> +out:
> + read_unlock(&domain->bounce_lock);
>
> return page;
> }
>
> static void
> -vduse_domain_free_bounce_pages(struct vduse_iova_domain *domain)
> +vduse_domain_free_kernel_bounce_pages(struct vduse_iova_domain *domain)
> {
> struct vduse_bounce_map *map;
> unsigned long pfn, bounce_pfns;
> @@ -243,6 +247,73 @@ vduse_domain_free_bounce_pages(struct vduse_iova_domain *domain)
> }
> }
>
> +int vduse_domain_add_user_bounce_pages(struct vduse_iova_domain *domain,
> + struct page **pages, int count)
> +{
> + struct vduse_bounce_map *map;
> + int i, ret;
> +
> + /* Now we don't support partial mapping */
> + if (count != (domain->bounce_size >> PAGE_SHIFT))
> + return -EINVAL;
> +
> + write_lock(&domain->bounce_lock);
> + ret = -EEXIST;
> + if (domain->user_bounce_pages)
> + goto out;
> +
> + for (i = 0; i < count; i++) {
> + map = &domain->bounce_maps[i];
> + if (map->bounce_page) {
> + /* Copy kernel page to user page if it's in use */
> + if (map->orig_phys != INVALID_PHYS_ADDR)
> + memcpy_to_page(pages[i], 0,
> + page_address(map->bounce_page),
> + PAGE_SIZE);
> + __free_page(map->bounce_page);
> + }
> + map->bounce_page = pages[i];
> + get_page(pages[i]);
> + }
> + domain->user_bounce_pages = true;
> + ret = 0;
> +out:
> + write_unlock(&domain->bounce_lock);
> +
> + return ret;
> +}
> +
> +void vduse_domain_remove_user_bounce_pages(struct vduse_iova_domain *domain)
> +{
> + struct vduse_bounce_map *map;
> + unsigned long i, count;
> +
> + write_lock(&domain->bounce_lock);
> + if (!domain->user_bounce_pages)
> + goto out;
> +
> + count = domain->bounce_size >> PAGE_SHIFT;
> + for (i = 0; i < count; i++) {
> + struct page *page = NULL;
> +
> + map = &domain->bounce_maps[i];
> + if (WARN_ON(!map->bounce_page))
> + continue;
> +
> + /* Copy user page to kernel page if it's in use */
> + if (map->orig_phys != INVALID_PHYS_ADDR) {
> + page = alloc_page(GFP_ATOMIC | __GFP_NOFAIL);
> + memcpy_from_page(page_address(page),
> + map->bounce_page, 0, PAGE_SIZE);
> + }
> + put_page(map->bounce_page);
> + map->bounce_page = page;
> + }
> + domain->user_bounce_pages = false;
> +out:
> + write_unlock(&domain->bounce_lock);
> +}
> +
> void vduse_domain_reset_bounce_map(struct vduse_iova_domain *domain)
> {
> if (!domain->bounce_map)
> @@ -318,13 +389,18 @@ dma_addr_t vduse_domain_map_page(struct vduse_iova_domain *domain,
> if (vduse_domain_init_bounce_map(domain))
> goto err;
>
> + read_lock(&domain->bounce_lock);
> if (vduse_domain_map_bounce_page(domain, (u64)iova, (u64)size, pa))
> - goto err;
> + goto err_unlock;
>
> if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
> vduse_domain_bounce(domain, iova, size, DMA_TO_DEVICE);
>
> + read_unlock(&domain->bounce_lock);
> +
> return iova;
> +err_unlock:
> + read_unlock(&domain->bounce_lock);
> err:
> vduse_domain_free_iova(iovad, iova, size);
> return DMA_MAPPING_ERROR;
> @@ -336,10 +412,12 @@ void vduse_domain_unmap_page(struct vduse_iova_domain *domain,
> {
> struct iova_domain *iovad = &domain->stream_iovad;
>
> + read_lock(&domain->bounce_lock);
> if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
> vduse_domain_bounce(domain, dma_addr, size, DMA_FROM_DEVICE);
>
> vduse_domain_unmap_bounce_page(domain, (u64)dma_addr, (u64)size);
> + read_unlock(&domain->bounce_lock);
> vduse_domain_free_iova(iovad, dma_addr, size);
> }
>
> @@ -447,7 +525,8 @@ static int vduse_domain_release(struct inode *inode, struct file *file)
>
> spin_lock(&domain->iotlb_lock);
> vduse_iotlb_del_range(domain, 0, ULLONG_MAX);
> - vduse_domain_free_bounce_pages(domain);
> + vduse_domain_remove_user_bounce_pages(domain);
> + vduse_domain_free_kernel_bounce_pages(domain);
> spin_unlock(&domain->iotlb_lock);
> put_iova_domain(&domain->stream_iovad);
> put_iova_domain(&domain->consistent_iovad);
> @@ -507,6 +586,7 @@ vduse_domain_create(unsigned long iova_limit, size_t bounce_size)
> goto err_file;
>
> domain->file = file;
> + rwlock_init(&domain->bounce_lock);
> spin_lock_init(&domain->iotlb_lock);
> init_iova_domain(&domain->stream_iovad,
> PAGE_SIZE, IOVA_START_PFN);
> diff --git a/drivers/vdpa/vdpa_user/iova_domain.h b/drivers/vdpa/vdpa_user/iova_domain.h
> index 2722d9b8e21a..4e0e50e7ac15 100644
> --- a/drivers/vdpa/vdpa_user/iova_domain.h
> +++ b/drivers/vdpa/vdpa_user/iova_domain.h
> @@ -14,6 +14,7 @@
> #include <linux/iova.h>
> #include <linux/dma-mapping.h>
> #include <linux/vhost_iotlb.h>
> +#include <linux/rwlock.h>
>
> #define IOVA_START_PFN 1
>
> @@ -34,6 +35,8 @@ struct vduse_iova_domain {
> struct vhost_iotlb *iotlb;
> spinlock_t iotlb_lock;
> struct file *file;
> + bool user_bounce_pages;
> + rwlock_t bounce_lock;
> };
>
> int vduse_domain_set_map(struct vduse_iova_domain *domain,
> @@ -61,6 +64,11 @@ void vduse_domain_free_coherent(struct vduse_iova_domain *domain, size_t size,
>
> void vduse_domain_reset_bounce_map(struct vduse_iova_domain *domain);
>
> +int vduse_domain_add_user_bounce_pages(struct vduse_iova_domain *domain,
> + struct page **pages, int count);
> +
> +void vduse_domain_remove_user_bounce_pages(struct vduse_iova_domain *domain);
> +
> void vduse_domain_destroy(struct vduse_iova_domain *domain);
>
> struct vduse_iova_domain *vduse_domain_create(unsigned long iova_limit,
> --
> 2.20.1
>

Next message: Akhil P Oommen: "Re: [Freedreno] [PATCH v2 5/7] arm64: dts: qcom: sc7280: Update gpu register list"
Previous message: Jason Wang: "Re: [PATCH v3 1/5] vduse: Remove unnecessary spin lock protection"
In reply to: Xie Yongji: "[PATCH v3 3/5] vduse: Support using userspace pages as bounce buffer"
Next in thread: Xie Yongji: "[PATCH v3 4/5] vduse: Support registering userspace memory for IOVA regions"
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