Re: [PATCH 09 of 14] swiotlb: support bouncing of HighMem pages

FUJITA Tomonori
2008-12-17T02:49:41Z

On Tue, 16 Dec 2008 12:17:33 -0800
Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> This requires us to treat DMA regions in terms of page+offset rather
> than virtual addressing since a HighMem page may not have a mapping.
>
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

Hmm, swiotlb should be architecture independent code.

Can you separate the following hack for only X86_32 from swiotlb? I
don't think that X86_64 and IA64 want such hack in core swiotbl code.

> lib/swiotlb.c | 120 +++++++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 88 insertions(+), 32 deletions(-)
>
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -26,6 +26,7 @@
> #include <linux/swiotlb.h>
> #include <linux/types.h>
> #include <linux/ctype.h>
> +#include <linux/highmem.h>
>
> #include <asm/io.h>
> #include <asm/dma.h>
> @@ -38,9 +39,6 @@
> #define OFFSET(val,align) ((unsigned long) \
> ( (val) & ( (align) - 1)))
>
> -#define SG_ENT_VIRT_ADDRESS(sg) (sg_virt((sg)))
> -#define SG_ENT_PHYS_ADDRESS(sg) virt_to_bus(SG_ENT_VIRT_ADDRESS(sg))
> -
> #define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
>
> /*
> @@ -91,7 +89,10 @@
> * We need to save away the original address corresponding to a mapped entry
> * for the sync operations.
> */
> -static unsigned char **io_tlb_orig_addr;
> +static struct swiotlb_phys_addr {
> + struct page *page;
> + unsigned int offset;
> +} *io_tlb_orig_addr;
>
> /*
> * Protect the above data structures in the map and unmap calls
> @@ -150,6 +151,11 @@
> return 0;
> }
>
> +static dma_addr_t swiotlb_sg_to_bus(struct scatterlist *sg)
> +{
> + return swiotlb_phys_to_bus(page_to_phys(sg_page(sg)) + sg->offset);
> +}
> +
> /*
> * Statically reserve bounce buffer space and initialize bounce buffer data
> * structures for the software IO TLB used to implement the DMA API.
> @@ -183,7 +189,7 @@
> for (i = 0; i < io_tlb_nslabs; i++)
> io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
> io_tlb_index = 0;
> - io_tlb_orig_addr = alloc_bootmem(io_tlb_nslabs * sizeof(char *));
> + io_tlb_orig_addr = alloc_bootmem(io_tlb_nslabs * sizeof(struct swiotlb_phys_addr));
>
> /*
> * Get the overflow emergency buffer
> @@ -258,12 +264,12 @@
> io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
> io_tlb_index = 0;
>
> - io_tlb_orig_addr = (unsigned char **)__get_free_pages(GFP_KERNEL,
> - get_order(io_tlb_nslabs * sizeof(char *)));
> + io_tlb_orig_addr = (struct swiotlb_phys_addr *)__get_free_pages(GFP_KERNEL,
> + get_order(io_tlb_nslabs * sizeof(struct swiotlb_phys_addr)));
> if (!io_tlb_orig_addr)
> goto cleanup3;
>
> - memset(io_tlb_orig_addr, 0, io_tlb_nslabs * sizeof(char *));
> + memset(io_tlb_orig_addr, 0, io_tlb_nslabs * sizeof(struct swiotlb_phys_addr));
>
> /*
> * Get the overflow emergency buffer
> @@ -312,20 +318,59 @@
> return addr >= io_tlb_start && addr < io_tlb_end;
> }
>
> +static struct swiotlb_phys_addr swiotlb_bus_to_phys_addr(char *dma_addr)
> +{
> + int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT;
> + struct swiotlb_phys_addr buffer = io_tlb_orig_addr[index];
> + buffer.offset += (long)dma_addr & ((1 << IO_TLB_SHIFT) - 1);
> + buffer.page += buffer.offset >> PAGE_SHIFT;
> + buffer.offset &= PAGE_SIZE - 1;
> + return buffer;
> +}
> +
> static void
> -__sync_single(char *buffer, char *dma_addr, size_t size, int dir)
> +__sync_single(struct swiotlb_phys_addr buffer, char *dma_addr, size_t size, int dir)
> {
> - if (dir == DMA_TO_DEVICE)
> - memcpy(dma_addr, buffer, size);
> - else
> - memcpy(buffer, dma_addr, size);
> + if (PageHighMem(buffer.page)) {
> + size_t len, bytes;
> + char *dev, *host, *kmp;
> +
> + len = size;
> + while (len != 0) {
> + unsigned long flags;
> +
> + bytes = len;
> + if ((bytes + buffer.offset) > PAGE_SIZE)
> + bytes = PAGE_SIZE - buffer.offset;
> + local_irq_save(flags); /* protects KM_BOUNCE_READ */
> + kmp = kmap_atomic(buffer.page, KM_BOUNCE_READ);
> + dev = dma_addr + size - len;
> + host = kmp + buffer.offset;
> + if (dir == DMA_FROM_DEVICE)
> + memcpy(host, dev, bytes);
> + else
> + memcpy(dev, host, bytes);
> + kunmap_atomic(kmp, KM_BOUNCE_READ);
> + local_irq_restore(flags);
> + len -= bytes;
> + buffer.page++;
> + buffer.offset = 0;
> + }
> + } else {
> + void *v = page_address(buffer.page) + buffer.offset;
> +
> + if (dir == DMA_TO_DEVICE)
> + memcpy(dma_addr, v, size);
> + else
> + memcpy(v, dma_addr, size);
> + }
> }
>
> /*
> * Allocates bounce buffer and returns its kernel virtual address.
> */
> static void *
> -map_single(struct device *hwdev, char *buffer, size_t size, int dir)
> +map_single(struct device *hwdev, struct swiotlb_phys_addr buffer, size_t size, int dir)
> {
> unsigned long flags;
> char *dma_addr;
> @@ -335,6 +380,7 @@
> unsigned long mask;
> unsigned long offset_slots;
> unsigned long max_slots;
> + struct swiotlb_phys_addr slot_buf;
>
> mask = dma_get_seg_boundary(hwdev);
> start_dma_addr = swiotlb_virt_to_bus(io_tlb_start) & mask;
> @@ -419,8 +465,13 @@
> * This is needed when we sync the memory. Then we sync the buffer if
> * needed.
> */
> - for (i = 0; i < nslots; i++)
> - io_tlb_orig_addr[index+i] = buffer + (i << IO_TLB_SHIFT);
> + slot_buf = buffer;
> + for (i = 0; i < nslots; i++) {
> + slot_buf.page += slot_buf.offset >> PAGE_SHIFT;
> + slot_buf.offset &= PAGE_SIZE - 1;
> + io_tlb_orig_addr[index+i] = slot_buf;
> + slot_buf.offset += 1 << IO_TLB_SHIFT;
> + }
> if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
> __sync_single(buffer, dma_addr, size, DMA_TO_DEVICE);
>
> @@ -436,12 +487,12 @@
> unsigned long flags;
> int i, count, nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
> int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT;
> - char *buffer = io_tlb_orig_addr[index];
> + struct swiotlb_phys_addr buffer = swiotlb_bus_to_phys_addr(dma_addr);
>
> /*
> * First, sync the memory before unmapping the entry
> */
> - if (buffer && ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
> + if ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL))
> /*
> * bounce... copy the data back into the original buffer * and
> * delete the bounce buffer.
> @@ -478,10 +529,7 @@
> sync_single(struct device *hwdev, char *dma_addr, size_t size,
> int dir, int target)
> {
> - int index = (dma_addr - io_tlb_start) >> IO_TLB_SHIFT;
> - char *buffer = io_tlb_orig_addr[index];
> -
> - buffer += ((unsigned long)dma_addr & ((1 << IO_TLB_SHIFT) - 1));
> + struct swiotlb_phys_addr buffer = swiotlb_bus_to_phys_addr(dma_addr);
>
> switch (target) {
> case SYNC_FOR_CPU:
> @@ -525,7 +573,10 @@
> * swiotlb_map_single(), which will grab memory from
> * the lowest available address range.
> */
> - ret = map_single(hwdev, NULL, size, DMA_FROM_DEVICE);
> + struct swiotlb_phys_addr buffer;
> + buffer.page = virt_to_page(NULL);
> + buffer.offset = 0;
> + ret = map_single(hwdev, buffer, size, DMA_FROM_DEVICE);
> if (!ret)
> return NULL;
> }
> @@ -593,6 +644,7 @@
> {
> dma_addr_t dev_addr = swiotlb_virt_to_bus(ptr);
> void *map;
> + struct swiotlb_phys_addr buffer;
>
> BUG_ON(dir == DMA_NONE);
> /*
> @@ -607,7 +659,9 @@
> /*
> * Oh well, have to allocate and map a bounce buffer.
> */
> - map = map_single(hwdev, ptr, size, dir);
> + buffer.page = virt_to_page(ptr);
> + buffer.offset = (unsigned long)ptr & ~PAGE_MASK;
> + map = map_single(hwdev, buffer, size, dir);
> if (!map) {
> swiotlb_full(hwdev, size, dir, 1);
> map = io_tlb_overflow_buffer;
> @@ -752,18 +806,20 @@
> int dir, struct dma_attrs *attrs)
> {
> struct scatterlist *sg;
> - void *addr;
> + struct swiotlb_phys_addr buffer;
> dma_addr_t dev_addr;
> int i;
>
> BUG_ON(dir == DMA_NONE);
>
> for_each_sg(sgl, sg, nelems, i) {
> - addr = SG_ENT_VIRT_ADDRESS(sg);
> - dev_addr = swiotlb_virt_to_bus(addr);
> + dev_addr = swiotlb_sg_to_bus(sg);
> if (range_needs_mapping(sg_virt(sg), sg->length) ||
> address_needs_mapping(hwdev, dev_addr, sg->length)) {
> - void *map = map_single(hwdev, addr, sg->length, dir);
> + void *map;
> + buffer.page = sg_page(sg);
> + buffer.offset = sg->offset;
> + map = map_single(hwdev, buffer, sg->length, dir);
> if (!map) {
> /* Don't panic here, we expect map_sg users
> to do proper error handling. */
> @@ -803,11 +859,11 @@
> BUG_ON(dir == DMA_NONE);
>
> for_each_sg(sgl, sg, nelems, i) {
> - if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
> + if (sg->dma_address != swiotlb_sg_to_bus(sg))
> unmap_single(hwdev, swiotlb_bus_to_virt(sg->dma_address),
> sg->dma_length, dir);
> else if (dir == DMA_FROM_DEVICE)
> - dma_mark_clean(SG_ENT_VIRT_ADDRESS(sg), sg->dma_length);
> + dma_mark_clean(swiotlb_bus_to_virt(sg->dma_address), sg->dma_length);
> }
> }
> EXPORT_SYMBOL(swiotlb_unmap_sg_attrs);
> @@ -836,11 +892,11 @@
> BUG_ON(dir == DMA_NONE);
>
> for_each_sg(sgl, sg, nelems, i) {
> - if (sg->dma_address != SG_ENT_PHYS_ADDRESS(sg))
> + if (sg->dma_address != swiotlb_sg_to_bus(sg))
> sync_single(hwdev, swiotlb_bus_to_virt(sg->dma_address),
> sg->dma_length, dir, target);
> else if (dir == DMA_FROM_DEVICE)
> - dma_mark_clean(SG_ENT_VIRT_ADDRESS(sg), sg->dma_length);
> + dma_mark_clean(swiotlb_bus_to_virt(sg->dma_address), sg->dma_length);
> }
> }
>
>
>
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