File 53ff3716-x86-ats-Disable-Address-Translation-Se... of Package xen

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File 53ff3716-x86-ats-Disable-Address-Translation-Services-by-default.patch of Package xen (Revision 7927bb8adb90295e52907a286ffb5b52)

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# Commit ad6eddb742577d182e634785bcfaf92732a50024
# Date 2014-08-28 16:05:10 +0200
# Author Andrew Cooper <andrew.cooper3@citrix.com>
# Committer Jan Beulich <jbeulich@suse.com>
x86/ats: Disable Address Translation Services by default

Xen cannot safely use any ATS functionality until it gains asynchronous queued
invalidation support, because of the current synchronous wait for completion.

Do not turn ATS on by default.

While editing the default in the command line documentation, correct the
statement regarding PCI Passthrough.  ATS is purely a performance
optimisation, and is certainly not required for PCI Passthrough to function.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -167,10 +167,13 @@ developers wishing Xen to fall back to o
 ### ats
 > `= <boolean>`
 
-> Default: `true`
+> Default: `false`
+
+Permits Xen to set up and use PCI Address Translation Services.  This is a
+performance optimisation for PCI Passthrough.
 
-Permits Xen to set up and use PCI Address Translation Services, which
-is required for PCI Passthrough.
+**WARNING: Xen cannot currently safely use ATS because of its synchronous wait
+loops for Queued Invalidation completions.**
 
 ### availmem
 > `= <size>`
--- a/xen/drivers/passthrough/x86/ats.c
+++ b/xen/drivers/passthrough/x86/ats.c
@@ -20,7 +20,7 @@
 
 LIST_HEAD(ats_devices);
 
-bool_t __read_mostly ats_enabled = 1;
+bool_t __read_mostly ats_enabled = 0;
 boolean_param("ats", ats_enabled);
 
 int enable_ats_device(int seg, int bus, int devfn, const void *iommu)

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File 53ff3716-x86-ats-Disable-Address-Translation-Services-by-default.patch of Package xen (Revision 7927bb8adb90295e52907a286ffb5b52)

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