Re: [Xen-devel] [PATCH v6 12/14] memory: add get_paged_gfn() as a wrapper...

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.08.18 at 11:47, <paul.durrant@xxxxxxxxxx> wrote:
> ...for some uses of get_page_from_gfn().
> 
> There are many occurences of the following pattern in the code:
> 
>     q = <readonly look-up> ? P2M_ALLOC : P2M_UNSHARE;

Especially with this UNSHARE in mind - is "paged" in the helper
function's name really suitable? Since we (I think) already have
get_gfn(), how about try_get_gfn()?

> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -350,34 +350,16 @@ static int hvmemul_do_io_buffer(
>  
>  static int hvmemul_acquire_page(unsigned long gmfn, struct page_info **page)
>  {
> -    struct domain *curr_d = current->domain;
> -    p2m_type_t p2mt;
> -
> -    *page = get_page_from_gfn(curr_d, gmfn, &p2mt, P2M_UNSHARE);
> -
> -    if ( *page == NULL )
> -        return X86EMUL_UNHANDLEABLE;
> -
> -    if ( p2m_is_paging(p2mt) )
> -    {
> -        put_page(*page);
> -        p2m_mem_paging_populate(curr_d, gmfn);
> -        return X86EMUL_RETRY;
> -    }
> -
> -    if ( p2m_is_shared(p2mt) )
> +    switch ( get_paged_gfn(current->domain, _gfn(gmfn), false, NULL, page) )
>      {
> -        put_page(*page);
> +    case -EAGAIN:
>          return X86EMUL_RETRY;
> -    }
> -
> -    /* This code should not be reached if the gmfn is not RAM */
> -    if ( p2m_is_mmio(p2mt) )
> -    {
> -        domain_crash(curr_d);
> -
> -        put_page(*page);
> +    case -EINVAL:
>          return X86EMUL_UNHANDLEABLE;
> +    default:
> +        ASSERT_UNREACHABLE();
> +    case 0:

I think you'd better have "default:" fall through to "case -EINVAL".
Similarly elsewhere.

> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -2557,24 +2557,12 @@ static void *_hvm_map_guest_frame(unsigned long gfn, 
> bool_t permanent,
>                                    bool_t *writable)
>  {
>      void *map;
> -    p2m_type_t p2mt;
>      struct page_info *page;
>      struct domain *d = current->domain;
> +    p2m_type_t p2mt;

???

Jan



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel