Re: [Xen-devel] [PATCH 17/21] xen: xen_ulong_t substitution

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 9 Oct 2012, Ian Campbell wrote:
> On Tue, 2012-10-09 at 13:39 +0100, Stefano Stabellini wrote:
> > On Fri, 5 Oct 2012, Ian Campbell wrote:
> > > On Fri, 2012-10-05 at 11:38 +0100, Ian Campbell wrote:
> > > > From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > > > 
> > > > There is still an unwanted unsigned long in the xen public interface:
> > > > replace it with xen_ulong_t.
> > > > 
> > > > Also typedef xen_ulong_t to uint64_t on ARM.
> > > 
> > > Should this change be applied to the uses of XEN_GUEST_HANDLE(ulong)
> > > too? My main concern is the one in struct gnttab_setup_table but there
> > > are a few others.
> > > 
> > > I suspect XEN_GUEST_HANDLE(ulong) needs to be removed entirely,
> > > everywhere it is used should be XEN_GUEST_HANDLE(xen_ulong_t) instead?
> > 
> > It is not necessary, because all the XEN_GUEST_HANDLE(ulong) are already
> > 64 bit on ARM. A 32 bit guest is going to pass a 32 bit unsigned long in a
> > 64 bit field, while a 64 bit guest is going to pass a 64 bit unsigned
> > long in a 64 bit field. Either way it will work.
> 
> XEN_GUEST_HANDLE(ulong) is unsigned long on all platforms, see
> xen/include/public/xen.h:
>         __DEFINE_XEN_GUEST_HANDLE(ulong, unsigned long);
> 
> The existence of this handle is dangerous since it contains a type which
> varies in size but it is (slightly) opaque so you might not notice.
> 
> The ulong handle is only really usable/desirable on x86 where retaining
> the ABI requires us to use unsigned long for some fields, but we have
> already defined xen_ulong_t which has the correct semantics on both ARM
> and x86.
> 
> I propose the following.

It is certainly an improvement. Also I didn't notice the
XEN_GUEST_HANDLE_PARAM(ulong): that is actually an error.
We also need a corresponding patch for Linux.


> 8<---------------------------------------------------
> 
> From 9090354c816216d6b9cc462e3e8c380e0001c554 Mon Sep 17 00:00:00 2001
> From: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Date: Fri, 5 Oct 2012 16:32:56 +0000
> Subject: [PATCH] xen: remove XEN_GUEST_HANDLE(ulong)
> 
> Having both this and XEN_GUEST_HANDLE(xen_ulong_t) is confusing and
> error prone.
> 
> Replace the two remaining uses of the ulong handle, in grant set and
> x86 set_gdt hypercalls, with xen_ulong_t.
> 
> This correctly sizes the grant frame entry as 64 bit on ARM but
> leaves it as unsigned long on x86 (therefore no intended change on
> x86). Likewise in set_gdt there is no actual change.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
>  xen/arch/x86/mm.c                |    3 ++-
>  xen/common/grant_table.c         |    2 +-
>  xen/include/asm-x86/hypercall.h  |    2 +-
>  xen/include/public/grant_table.h |    2 +-
>  xen/include/public/xen.h         |    2 --
>  5 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
> index f9a41fd..3a11af0 100644
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -4100,7 +4100,8 @@ long set_gdt(struct vcpu *v,
>  }
>  
>  
> -long do_set_gdt(XEN_GUEST_HANDLE_PARAM(ulong) frame_list, unsigned int 
> entries)
> +long do_set_gdt(XEN_GUEST_HANDLE_PARAM(xen_ulong_t) frame_list,
> +                unsigned int entries)
>  {
>      int nr_pages = (entries + 511) / 512;
>      unsigned long frames[16];
> diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
> index f4ae9ee..7912769 100644
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -1322,7 +1322,7 @@ gnttab_setup_table(
>      struct domain *d;
>      struct grant_table *gt;
>      int            i;
> -    unsigned long  gmfn;
> +    xen_pfn_t  gmfn;
>  
>      if ( count != 1 )
>          return -EINVAL;
> diff --git a/xen/include/asm-x86/hypercall.h b/xen/include/asm-x86/hypercall.h
> index bd14220..afa8ba9 100644
> --- a/xen/include/asm-x86/hypercall.h
> +++ b/xen/include/asm-x86/hypercall.h
> @@ -33,7 +33,7 @@ do_mmu_update(
>  
>  extern long
>  do_set_gdt(
> -    XEN_GUEST_HANDLE_PARAM(ulong) frame_list,
> +    XEN_GUEST_HANDLE_PARAM(xen_ulong_t) frame_list,
>      unsigned int entries);
>  
>  extern long
> diff --git a/xen/include/public/grant_table.h 
> b/xen/include/public/grant_table.h
> index 28d9476..13cc559 100644
> --- a/xen/include/public/grant_table.h
> +++ b/xen/include/public/grant_table.h
> @@ -385,7 +385,7 @@ struct gnttab_setup_table {
>      uint32_t nr_frames;
>      /* OUT parameters. */
>      int16_t  status;              /* => enum grant_status */
> -    XEN_GUEST_HANDLE(ulong) frame_list;
> +    XEN_GUEST_HANDLE(xen_pfn_t) frame_list;
>  };
>  typedef struct gnttab_setup_table gnttab_setup_table_t;
>  DEFINE_XEN_GUEST_HANDLE(gnttab_setup_table_t);
> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> index e42d01f..9a5b394 100644
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -43,8 +43,6 @@ DEFINE_XEN_GUEST_HANDLE(char);
>  __DEFINE_XEN_GUEST_HANDLE(uchar, unsigned char);
>  DEFINE_XEN_GUEST_HANDLE(int);
>  __DEFINE_XEN_GUEST_HANDLE(uint,  unsigned int);
> -DEFINE_XEN_GUEST_HANDLE(long);
> -__DEFINE_XEN_GUEST_HANDLE(ulong, unsigned long);
>  DEFINE_XEN_GUEST_HANDLE(void);
>  
>  DEFINE_XEN_GUEST_HANDLE(uint64_t);
> -- 
> 1.7.9.1
> 
> 
> 
> 

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