Re: [PATCH RFC v1 3/7] swiotlb-xen: support highmem for xen specific code

[Christoph Hellwig]

On Wed, Jun 08, 2022 at 05:55:49PM -0700, Dongli Zhang wrote:
> @@ -109,19 +110,25 @@ int xen_swiotlb_fixup(void *buf, unsigned long nslabs, 
> bool high)
>   int rc;
>   unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);
>   unsigned int i, dma_bits = order + PAGE_SHIFT;
> + unsigned int max_dma_bits = MAX_DMA32_BITS;
>   dma_addr_t dma_handle;
>   phys_addr_t p = virt_to_phys(buf);
>  
>   BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));
>   BUG_ON(nslabs % IO_TLB_SEGSIZE);
>  
> + if (high) {
> + dma_bits = MAX_DMA64_BITS;
> + max_dma_bits = MAX_DMA64_BITS;
> + }
> +

I think you really want to pass the addressing bits or mask to the
remap callback and not do magic with a 'high' flag here.
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[PATCH RFC v1 3/7] swiotlb-xen: support highmem for xen specific code

[Dongli Zhang]

While for most of times the swiotlb-xen relies on the generic swiotlb api
to initialize and use swiotlb, this patch is to support highmem swiotlb
for swiotlb-xen specific code.

E.g., the xen_swiotlb_fixup() may request the hypervisor to provide
64-bit memory pages as swiotlb buffer.

Cc: Konrad Wilk 
Cc: Joe Jin 
Signed-off-by: Dongli Zhang 
---
 drivers/xen/swiotlb-xen.c | 14 +++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 339f46e21053..d15321e9f9db 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -38,7 +38,8 @@
 #include 
 
 #include 
-#define MAX_DMA_BITS 32
+#define MAX_DMA32_BITS 32
+#define MAX_DMA64_BITS 64
 
 /*
  * Quick lookup value of the bus address of the IOTLB.
@@ -109,19 +110,25 @@ int xen_swiotlb_fixup(void *buf, unsigned long nslabs, 
bool high)
int rc;
unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);
unsigned int i, dma_bits = order + PAGE_SHIFT;
+   unsigned int max_dma_bits = MAX_DMA32_BITS;
dma_addr_t dma_handle;
phys_addr_t p = virt_to_phys(buf);
 
BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));
BUG_ON(nslabs % IO_TLB_SEGSIZE);
 
+   if (high) {
+   dma_bits = MAX_DMA64_BITS;
+   max_dma_bits = MAX_DMA64_BITS;
+   }
+
i = 0;
do {
do {
rc = xen_create_contiguous_region(
p + (i << IO_TLB_SHIFT), order,
dma_bits, _handle);
-   } while (rc && dma_bits++ < MAX_DMA_BITS);
+   } while (rc && dma_bits++ < max_dma_bits);
if (rc)
return rc;
 
@@ -381,7 +388,8 @@ xen_swiotlb_sync_sg_for_device(struct device *dev, struct 
scatterlist *sgl,
 static int
 xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
 {
-   return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask;
+   return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask ||
+  xen_phys_to_dma(hwdev, io_tlb_high_mem.end - 1) <= mask;
 }
 
 const struct dma_map_ops xen_swiotlb_dma_ops = {
-- 
2.17.1

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