VT-d Posted-Interrupts is an enhancement to CPU side Posted-Interrupt.
With VT-d Posted-Interrupts enabled, external interrupts from
direct-assigned devices can be delivered to guests without VMM
intervention when guest is running in non-root mode.
This patch adds variable 'iommu_intpost' to control whether enable VT-d
posted-interrupt or not in the generic IOMMU code.
CC: Jan Beulich <jbeul...@suse.com>
CC: Kevin Tian <kevin.t...@intel.com>
Signed-off-by: Feng Wu <feng...@intel.com>
Reviewed-by: Kevin Tian <kevin.t...@intel.com>
---
v4:
- No changes
v3:
- Remove pointless initializer for 'iommu_intpost'.
- Some adjustment for "if no intremap then no intpost" logic.
* For parse_iommu_param(), move it to the end of the function,
so we don't need to add the some logic when introduing the
new kernel parameter 'intpost' in later patch.
* Add this logic in iommu_setup() after iommu_hardware_setup()
is called.
xen/drivers/passthrough/iommu.c | 17 ++++++++++++++++-
xen/include/xen/iommu.h | 2 +-
2 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 06cb38f..536b69f 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -39,6 +39,7 @@ static void iommu_dump_p2m_table(unsigned char key);
* no-snoop Disable VT-d Snoop Control
* no-qinval Disable VT-d Queued Invalidation
* no-intremap Disable VT-d Interrupt Remapping
+ * no-intpost Disable VT-d Interrupt posting
*/
custom_param("iommu", parse_iommu_param);
bool_t __initdata iommu_enable = 1;
@@ -51,6 +52,14 @@ bool_t __read_mostly iommu_passthrough;
bool_t __read_mostly iommu_snoop = 1;
bool_t __read_mostly iommu_qinval = 1;
bool_t __read_mostly iommu_intremap = 1;
+
+/*
+ * In the current implementation of VT-d posted interrupts, in some extreme
+ * cases, the per cpu list which saves the blocked vCPU will be very long,
+ * and this will affect the interrupt latency, so let this feature off by
+ * default until we find a good solution to resolve it.
+ */
+bool_t __read_mostly iommu_intpost;
bool_t __read_mostly iommu_hap_pt_share = 1;
bool_t __read_mostly iommu_debug;
bool_t __read_mostly amd_iommu_perdev_intremap = 1;
@@ -112,6 +121,9 @@ static void __init parse_iommu_param(char *s)
s = ss + 1;
} while ( ss );
+
+ if ( !iommu_intremap )
+ iommu_intpost = 0;
}
int iommu_domain_init(struct domain *d)
@@ -305,6 +317,9 @@ int __init iommu_setup(void)
panic("Couldn't enable %s and iommu=required/force",
!iommu_enabled ? "IOMMU" : "Interrupt Remapping");
+ if ( !iommu_intremap )
+ iommu_intpost = 0;
+
if ( !iommu_enabled )
{
iommu_snoop = 0;
@@ -372,7 +387,7 @@ void iommu_crash_shutdown(void)
const struct iommu_ops *ops = iommu_get_ops();
if ( iommu_enabled )
ops->crash_shutdown();
- iommu_enabled = iommu_intremap = 0;
+ iommu_enabled = iommu_intremap = iommu_intpost = 0;
}
bool_t iommu_has_feature(struct domain *d, enum iommu_feature feature)
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index b30bf41..a123cce 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -31,7 +31,7 @@
extern bool_t iommu_enable, iommu_enabled;
extern bool_t force_iommu, iommu_verbose;
extern bool_t iommu_workaround_bios_bug, iommu_passthrough;
-extern bool_t iommu_snoop, iommu_qinval, iommu_intremap;
+extern bool_t iommu_snoop, iommu_qinval, iommu_intremap, iommu_intpost;
extern bool_t iommu_hap_pt_share;
extern bool_t iommu_debug;
extern bool_t amd_iommu_perdev_intremap;
--
2.1.0
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