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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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.

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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