50 lines
1.7 KiB
Diff
50 lines
1.7 KiB
Diff
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# Commit ad6eddb742577d182e634785bcfaf92732a50024
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# Date 2014-08-28 16:05:10 +0200
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# Author Andrew Cooper <andrew.cooper3@citrix.com>
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# Committer Jan Beulich <jbeulich@suse.com>
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x86/ats: Disable Address Translation Services by default
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Xen cannot safely use any ATS functionality until it gains asynchronous queued
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invalidation support, because of the current synchronous wait for completion.
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Do not turn ATS on by default.
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While editing the default in the command line documentation, correct the
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statement regarding PCI Passthrough. ATS is purely a performance
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optimisation, and is certainly not required for PCI Passthrough to function.
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Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Reviewed-by: Jan Beulich <jbeulich@suse.com>
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Acked-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
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--- a/docs/misc/xen-command-line.markdown
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+++ b/docs/misc/xen-command-line.markdown
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@@ -167,10 +167,13 @@ developers wishing Xen to fall back to o
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### ats
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> `= <boolean>`
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-> Default: `true`
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+> Default: `false`
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+
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+Permits Xen to set up and use PCI Address Translation Services. This is a
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+performance optimisation for PCI Passthrough.
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-Permits Xen to set up and use PCI Address Translation Services, which
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-is required for PCI Passthrough.
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+**WARNING: Xen cannot currently safely use ATS because of its synchronous wait
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+loops for Queued Invalidation completions.**
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### availmem
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> `= <size>`
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--- a/xen/drivers/passthrough/x86/ats.c
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+++ b/xen/drivers/passthrough/x86/ats.c
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@@ -20,7 +20,7 @@
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LIST_HEAD(ats_devices);
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-bool_t __read_mostly ats_enabled = 1;
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+bool_t __read_mostly ats_enabled = 0;
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boolean_param("ats", ats_enabled);
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int enable_ats_device(int seg, int bus, int devfn, const void *iommu)
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