[PATCH] x86/HVM: correct last address emulation acceptance check

[PATCH] x86/HVM: correct last address emulation acceptance check

[Jan Beulich]

[-- Attachment #1: Type: text/plain, Size: 1069 bytes --]

For REPeated memory access instructions the repeat count also needs to
be considered. Utilize that "last" already takes this into account.

Also defer computing "last" until we really know we need it.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/hvm/intercept.c
+++ b/xen/arch/x86/hvm/intercept.c
@@ -34,16 +34,16 @@
 static bool_t hvm_mmio_accept(const struct hvm_io_handler *handler,
                               const ioreq_t *p)
 {
-    paddr_t first = hvm_mmio_first_byte(p);
-    paddr_t last = hvm_mmio_last_byte(p);
+    paddr_t first = hvm_mmio_first_byte(p), last;
 
     BUG_ON(handler->type != IOREQ_TYPE_COPY);
 
     if ( !handler->mmio.ops->check(current, first) )
         return 0;
 
-    /* Make sure the handler will accept the whole access */
-    if ( p->size > 1 &&
+    /* Make sure the handler will accept the whole access. */
+    last = hvm_mmio_last_byte(p);
+    if ( last != first &&
          !handler->mmio.ops->check(current, last) )
         domain_crash(current->domain);
 




[-- Attachment #2: x86-HVM-MMIO-accept-rep.patch --]
[-- Type: text/plain, Size: 1123 bytes --]

x86/HVM: correct last address emulation acceptance check

For REPeated memory access instructions the repeat count also needs to
be considered. Utilize that "last" already takes this into account.

Also defer computing "last" until we really know we need it.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/hvm/intercept.c
+++ b/xen/arch/x86/hvm/intercept.c
@@ -34,16 +34,16 @@
 static bool_t hvm_mmio_accept(const struct hvm_io_handler *handler,
                               const ioreq_t *p)
 {
-    paddr_t first = hvm_mmio_first_byte(p);
-    paddr_t last = hvm_mmio_last_byte(p);
+    paddr_t first = hvm_mmio_first_byte(p), last;
 
     BUG_ON(handler->type != IOREQ_TYPE_COPY);
 
     if ( !handler->mmio.ops->check(current, first) )
         return 0;
 
-    /* Make sure the handler will accept the whole access */
-    if ( p->size > 1 &&
+    /* Make sure the handler will accept the whole access. */
+    last = hvm_mmio_last_byte(p);
+    if ( last != first &&
          !handler->mmio.ops->check(current, last) )
         domain_crash(current->domain);
 

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Re: [PATCH] x86/HVM: correct last address emulation acceptance check

[Paul Durrant]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: 26 April 2016 09:23
> To: xen-devel
> Cc: Paul Durrant; Wei Liu
> Subject: [PATCH] x86/HVM: correct last address emulation acceptance check
> 
> For REPeated memory access instructions the repeat count also needs to
> be considered. Utilize that "last" already takes this into account.
> 
> Also defer computing "last" until we really know we need it.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

> 
> --- a/xen/arch/x86/hvm/intercept.c
> +++ b/xen/arch/x86/hvm/intercept.c
> @@ -34,16 +34,16 @@
>  static bool_t hvm_mmio_accept(const struct hvm_io_handler *handler,
>                                const ioreq_t *p)
>  {
> -    paddr_t first = hvm_mmio_first_byte(p);
> -    paddr_t last = hvm_mmio_last_byte(p);
> +    paddr_t first = hvm_mmio_first_byte(p), last;
> 
>      BUG_ON(handler->type != IOREQ_TYPE_COPY);
> 
>      if ( !handler->mmio.ops->check(current, first) )
>          return 0;
> 
> -    /* Make sure the handler will accept the whole access */
> -    if ( p->size > 1 &&
> +    /* Make sure the handler will accept the whole access. */
> +    last = hvm_mmio_last_byte(p);
> +    if ( last != first &&
>           !handler->mmio.ops->check(current, last) )
>          domain_crash(current->domain);
> 
> 
> 


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Re: [PATCH] x86/HVM: correct last address emulation acceptance check

[Wei Liu]

On Tue, Apr 26, 2016 at 02:22:50AM -0600, Jan Beulich wrote:
> For REPeated memory access instructions the repeat count also needs to
> be considered. Utilize that "last" already takes this into account.
> 
> Also defer computing "last" until we really know we need it.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Release-acked-by: Wei Liu <wei.liu2@citrix.com>

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