svn commit: r302635 - in head/sys: amd64/include i386/include x86/x86 x86/xen

[Roger Pau Monné]

Author: royger
Date: Tue Jul 12 08:43:09 2016
New Revision: 302635
URL: https://svnweb.freebsd.org/changeset/base/302635

Log:
  xen: automatically disable MSI-X interrupt migration
  
  If the hypervisor version is smaller than 4.6.0. Xen commits 74fd00 and
  70a3cb are required on the hypervisor side for this to be fixed, and those
  are only included in 4.6.0, so stay on the safe side and disable MSI-X
  interrupt migration on anything older than 4.6.0.
  
  It should not cause major performance degradation unless a lot of MSI-X
  interrupts are allocated.
  
  Sponsored by:		Citrix Systems R&D
  MFC after:		3 days
  Reviewed by:		jhb
  Differential revision:	https://reviews.freebsd.org/D7148

Modified:
  head/sys/amd64/include/intr_machdep.h
  head/sys/i386/include/intr_machdep.h
  head/sys/x86/x86/msi.c
  head/sys/x86/xen/hvm.c

Modified: head/sys/amd64/include/intr_machdep.h
==============================================================================
--- head/sys/amd64/include/intr_machdep.h	Tue Jul 12 08:38:03 2016	(r302634)
+++ head/sys/amd64/include/intr_machdep.h	Tue Jul 12 08:43:09 2016	(r302635)
@@ -149,6 +149,8 @@ extern cpuset_t intr_cpus;
 extern struct mtx icu_lock;
 extern int elcr_found;
 
+extern int msix_disable_migration;
+
 #ifndef DEV_ATPIC
 void	atpic_reset(void);
 #endif

Modified: head/sys/i386/include/intr_machdep.h
==============================================================================
--- head/sys/i386/include/intr_machdep.h	Tue Jul 12 08:38:03 2016	(r302634)
+++ head/sys/i386/include/intr_machdep.h	Tue Jul 12 08:43:09 2016	(r302635)
@@ -140,6 +140,8 @@ extern cpuset_t intr_cpus;
 extern struct mtx icu_lock;
 extern int elcr_found;
 
+extern int msix_disable_migration;
+
 #ifndef DEV_ATPIC
 void	atpic_reset(void);
 #endif

Modified: head/sys/x86/x86/msi.c
==============================================================================
--- head/sys/x86/x86/msi.c	Tue Jul 12 08:38:03 2016	(r302634)
+++ head/sys/x86/x86/msi.c	Tue Jul 12 08:43:09 2016	(r302635)
@@ -149,12 +149,16 @@ struct pic msi_pic = {
 	.pic_reprogram_pin = NULL,
 };
 
-/*
+/**
  * Xen hypervisors prior to 4.6.0 do not properly handle updates to
  * enabled MSI-X table entries.  Allow migration of MSI-X interrupts
- * to be disabled via a tunable.
+ * to be disabled via a tunable. Values have the following meaning:
+ *
+ * -1: automatic detection by FreeBSD
+ *  0: enable migration
+ *  1: disable migration
  */
-static int msix_disable_migration = 0;
+int msix_disable_migration = -1;
 SYSCTL_INT(_machdep, OID_AUTO, disable_msix_migration, CTLFLAG_RDTUN,
     &msix_disable_migration, 0,
     "Disable migration of MSI-X interrupts between CPUs");
@@ -312,6 +316,11 @@ msi_init(void)
 		return;
 	}
 
+	if (msix_disable_migration == -1) {
+		/* The default is to allow migration of MSI-X interrupts. */
+		msix_disable_migration = 0;
+	}
+
 	msi_enabled = 1;
 	intr_register_pic(&msi_pic);
 	mtx_init(&msi_lock, "msi", NULL, MTX_DEF);

Modified: head/sys/x86/xen/hvm.c
==============================================================================
--- head/sys/x86/xen/hvm.c	Tue Jul 12 08:38:03 2016	(r302634)
+++ head/sys/x86/xen/hvm.c	Tue Jul 12 08:43:09 2016	(r302635)
@@ -134,9 +134,29 @@ xen_hvm_init_hypercall_stubs(enum xen_hv
 		return (ENXIO);
 
 	if (init_type == XEN_HVM_INIT_COLD) {
+		int major, minor;
+
 		do_cpuid(base + 1, regs);
-		printf("XEN: Hypervisor version %d.%d detected.\n",
-		    regs[0] >> 16, regs[0] & 0xffff);
+
+		major = regs[0] >> 16;
+		minor = regs[0] & 0xffff;
+		printf("XEN: Hypervisor version %d.%d detected.\n", major,
+			minor);
+
+		if (((major < 4) || (major == 4 && minor <= 5)) &&
+		    msix_disable_migration == -1) {
+			/*
+			 * Xen hypervisors prior to 4.6.0 do not properly
+			 * handle updates to enabled MSI-X table entries,
+			 * so disable MSI-X interrupt migration in that
+			 * case.
+			 */
+			if (bootverbose)
+				printf(
+"Disabling MSI-X interrupt migration due to Xen hypervisor bug.\n"
+"Set machdep.msix_disable_migration=0 to forcefully enable it.\n");
+			msix_disable_migration = 1;
+		}
 	}
 
 	/*