[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Xen-devel] [PATCH] x86/PCI: fix guest_io_read() when pci_cfg_ok() denies access


  • To: "xen-devel" <xen-devel@xxxxxxxxxxxxx>
  • From: "Jan Beulich" <JBeulich@xxxxxxxx>
  • Date: Thu, 21 Jun 2012 13:17:55 +0100
  • Delivery-date: Thu, 21 Jun 2012 12:17:34 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>

For a multi-byte aligned read, this so far resulted in 0x00ff to be
put in the guest's register rather than 0xffff or 0xffffffff, which in
turn could confuse bus scanning functions (which, when reading vendor
and/or device IDs, expect to get back all zeroes or all ones).

As the value gets masked to the read width when merging back into the
full result, setting the initial value to all ones should not harm any
or the other cases.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1717,7 +1717,7 @@ static uint32_t guest_io_read(
     while ( bytes != 0 )
     {
         unsigned int size = 1;
-        uint32_t sub_data = 0xff;
+        uint32_t sub_data = ~0;
 
         if ( (port == 0x42) || (port == 0x43) || (port == 0x61) )
         {



Attachment: x86-PCI-config-read-not-ok.patch
Description: Text document

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.