Re: [Xen-devel] [PATCH v6 09/16] x86/hvm: limit reps to avoid the need to handle retry

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.07.15 at 18:25, <paul.durrant@xxxxxxxxxx> wrote:
> @@ -287,17 +271,56 @@ static int hvmemul_do_io_addr(
>      bool_t is_mmio, paddr_t addr, unsigned long *reps,
>      unsigned int size, uint8_t dir, bool_t df, paddr_t ram_gpa)
>  {
> -    struct page_info *ram_page;
> +    struct vcpu *v = current;
> +    unsigned long ram_gmfn = paddr_to_pfn(ram_gpa);
> +    unsigned int page_off = ram_gpa & (PAGE_SIZE - 1);
> +    struct page_info *ram_page[2];
> +    int nr_pages = 0;

unsigned int

> +    unsigned long count;
>      int rc;
>  
> -    rc = hvmemul_acquire_page(paddr_to_pfn(ram_gpa), &ram_page);
> +    rc = hvmemul_acquire_page(ram_gmfn, &ram_page[nr_pages]);
>      if ( rc != X86EMUL_OKAY )
> -        return rc;
> +        goto out;
>  
> -    rc = hvmemul_do_io(is_mmio, addr, reps, size, dir, df, 1,
> +    nr_pages++;
> +
> +    /* Detemine how many reps will fit within this page */

"Determine" and missing stop.

> +    count = min_t(unsigned long,
> +                  *reps,
> +                  df ?
> +                  (page_off + size - 1) / size :

Looks like this won't be correct for the page crossing case (where
the code below really expects to see zero). I think you simply need
to mask with (PAGE_SIZE - 1) again here before dividing.

> @@ -468,6 +469,9 @@ void hvm_do_resume(struct vcpu *v)
>          }
>      }
>  
> +    if ( vio->mmio_retry )
> +        (void)handle_mmio();

Pointless cast.

Jan


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