Re: [Resend RFC PATCH V2 09/12] swiotlb: Add bounce buffer remap address setting function

2021-04-15 Thread Konrad Rzeszutek Wilk
On Wed, Apr 14, 2021 at 10:49:42AM -0400, Tianyu Lan wrote:
> From: Tianyu Lan 
> 
> For Hyper-V isolation VM with AMD SEV SNP, the bounce buffer(shared memory)
> needs to be accessed via extra address space(e.g address above bit39).
> Hyper-V code may remap extra address space outside of swiotlb. 
> swiotlb_bounce()

May? Isn't this a MUST in this case?

> needs to use remap virtual address to copy data from/to bounce buffer. Add
> new interface swiotlb_set_bounce_remap() to do that.

I am bit lost - why can't you use the swiotlb_init and pass in your
DMA pool that is already above bit 39?

> 
> Signed-off-by: Tianyu Lan 
> ---
>  include/linux/swiotlb.h |  5 +
>  kernel/dma/swiotlb.c| 13 -
>  2 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index d9c9fc9ca5d2..3ccd08116683 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -82,8 +82,13 @@ unsigned int swiotlb_max_segment(void);
>  size_t swiotlb_max_mapping_size(struct device *dev);
>  bool is_swiotlb_active(void);
>  void __init swiotlb_adjust_size(unsigned long new_size);
> +void swiotlb_set_bounce_remap(unsigned char *vaddr);
>  #else
>  #define swiotlb_force SWIOTLB_NO_FORCE
> +static inline void swiotlb_set_bounce_remap(unsigned char *vaddr)
> +{
> +}
> +
>  static inline bool is_swiotlb_buffer(phys_addr_t paddr)
>  {
>   return false;
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 7c42df6e6100..5fd2db6aa149 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -94,6 +94,7 @@ static unsigned int io_tlb_index;
>   * not be bounced (unless SWIOTLB_FORCE is set).
>   */
>  static unsigned int max_segment;
> +static unsigned char *swiotlb_bounce_remap_addr;
>  
>  /*
>   * We need to save away the original address corresponding to a mapped entry
> @@ -421,6 +422,11 @@ void __init swiotlb_exit(void)
>   swiotlb_cleanup();
>  }
>  
> +void swiotlb_set_bounce_remap(unsigned char *vaddr)
> +{
> + swiotlb_bounce_remap_addr = vaddr;
> +}
> +
>  /*
>   * Bounce: copy the swiotlb buffer from or back to the original dma location
>   */
> @@ -428,7 +434,12 @@ static void swiotlb_bounce(phys_addr_t orig_addr, 
> phys_addr_t tlb_addr,
>  size_t size, enum dma_data_direction dir)
>  {
>   unsigned long pfn = PFN_DOWN(orig_addr);
> - unsigned char *vaddr = phys_to_virt(tlb_addr);
> + unsigned char *vaddr;
> +
> + if (swiotlb_bounce_remap_addr)
> + vaddr = swiotlb_bounce_remap_addr + tlb_addr - io_tlb_start;
> + else
> + vaddr = phys_to_virt(tlb_addr);
>  
>   if (PageHighMem(pfn_to_page(pfn))) {
>   /* The buffer does not have a mapping.  Map it in and copy */
> -- 
> 2.25.1
> 


[Resend RFC PATCH V2 09/12] swiotlb: Add bounce buffer remap address setting function

2021-04-14 Thread Tianyu Lan
From: Tianyu Lan 

For Hyper-V isolation VM with AMD SEV SNP, the bounce buffer(shared memory)
needs to be accessed via extra address space(e.g address above bit39).
Hyper-V code may remap extra address space outside of swiotlb. swiotlb_bounce()
needs to use remap virtual address to copy data from/to bounce buffer. Add
new interface swiotlb_set_bounce_remap() to do that.

Signed-off-by: Tianyu Lan 
---
 include/linux/swiotlb.h |  5 +
 kernel/dma/swiotlb.c| 13 -
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index d9c9fc9ca5d2..3ccd08116683 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -82,8 +82,13 @@ unsigned int swiotlb_max_segment(void);
 size_t swiotlb_max_mapping_size(struct device *dev);
 bool is_swiotlb_active(void);
 void __init swiotlb_adjust_size(unsigned long new_size);
+void swiotlb_set_bounce_remap(unsigned char *vaddr);
 #else
 #define swiotlb_force SWIOTLB_NO_FORCE
+static inline void swiotlb_set_bounce_remap(unsigned char *vaddr)
+{
+}
+
 static inline bool is_swiotlb_buffer(phys_addr_t paddr)
 {
return false;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 7c42df6e6100..5fd2db6aa149 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -94,6 +94,7 @@ static unsigned int io_tlb_index;
  * not be bounced (unless SWIOTLB_FORCE is set).
  */
 static unsigned int max_segment;
+static unsigned char *swiotlb_bounce_remap_addr;
 
 /*
  * We need to save away the original address corresponding to a mapped entry
@@ -421,6 +422,11 @@ void __init swiotlb_exit(void)
swiotlb_cleanup();
 }
 
+void swiotlb_set_bounce_remap(unsigned char *vaddr)
+{
+   swiotlb_bounce_remap_addr = vaddr;
+}
+
 /*
  * Bounce: copy the swiotlb buffer from or back to the original dma location
  */
@@ -428,7 +434,12 @@ static void swiotlb_bounce(phys_addr_t orig_addr, 
phys_addr_t tlb_addr,
   size_t size, enum dma_data_direction dir)
 {
unsigned long pfn = PFN_DOWN(orig_addr);
-   unsigned char *vaddr = phys_to_virt(tlb_addr);
+   unsigned char *vaddr;
+
+   if (swiotlb_bounce_remap_addr)
+   vaddr = swiotlb_bounce_remap_addr + tlb_addr - io_tlb_start;
+   else
+   vaddr = phys_to_virt(tlb_addr);
 
if (PageHighMem(pfn_to_page(pfn))) {
/* The buffer does not have a mapping.  Map it in and copy */
-- 
2.25.1