svn commit: r303776 - in stable/10/sys: amd64/include i386/include x86/x86 x86/xen
John Baldwin
jhb at FreeBSD.org
Fri Aug 5 17:13:27 UTC 2016
Author: jhb
Date: Fri Aug 5 17:13:25 2016
New Revision: 303776
URL: https://svnweb.freebsd.org/changeset/base/303776
Log:
MFC 302181,302635: Disable MSI-X migration on older Xen hypervisors.
302181:
Add a tunable to disable migration of MSI-X interrupts.
The new 'machdep.disable_msix_migration' tunable can be set to 1 to
disable migration of MSI-X interrupts.
Xen versions prior to 4.6.0 do not properly handle updates to MSI-X
table entries after the initial write. In particular, the operation
to unmask a table entry after updating it during migration is not
propagated to the "real" table for passthrough devices causing the
interrupt to remain masked. At least some systems in EC2 are
affected by this bug when using SRIOV. The tunable can be set in
loader.conf as a workaround.
302635:
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.
Modified:
stable/10/sys/amd64/include/intr_machdep.h
stable/10/sys/i386/include/intr_machdep.h
stable/10/sys/x86/x86/msi.c
stable/10/sys/x86/xen/hvm.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/amd64/include/intr_machdep.h
==============================================================================
--- stable/10/sys/amd64/include/intr_machdep.h Fri Aug 5 16:53:24 2016 (r303775)
+++ stable/10/sys/amd64/include/intr_machdep.h Fri Aug 5 17:13:25 2016 (r303776)
@@ -144,6 +144,8 @@ struct nmi_pcpu {
extern struct mtx icu_lock;
extern int elcr_found;
+extern int msix_disable_migration;
+
#ifndef DEV_ATPIC
void atpic_reset(void);
#endif
Modified: stable/10/sys/i386/include/intr_machdep.h
==============================================================================
--- stable/10/sys/i386/include/intr_machdep.h Fri Aug 5 16:53:24 2016 (r303775)
+++ stable/10/sys/i386/include/intr_machdep.h Fri Aug 5 17:13:25 2016 (r303776)
@@ -141,6 +141,8 @@ struct trapframe;
extern struct mtx icu_lock;
extern int elcr_found;
+extern int msix_disable_migration;
+
#ifndef DEV_ATPIC
void atpic_reset(void);
#endif
Modified: stable/10/sys/x86/x86/msi.c
==============================================================================
--- stable/10/sys/x86/x86/msi.c Fri Aug 5 16:53:24 2016 (r303775)
+++ stable/10/sys/x86/x86/msi.c Fri Aug 5 17:13:25 2016 (r303776)
@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/sx.h>
+#include <sys/sysctl.h>
#include <sys/systm.h>
#include <x86/apicreg.h>
#include <machine/cputypes.h>
@@ -134,6 +135,20 @@ struct pic msi_pic = { msi_enable_source
msi_source_pending, NULL, NULL, msi_config_intr,
msi_assign_cpu };
+/**
+ * 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. Values have the following meaning:
+ *
+ * -1: automatic detection by FreeBSD
+ * 0: enable migration
+ * 1: disable migration
+ */
+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");
+
static int msi_enabled;
static int msi_last_irq;
static struct mtx msi_lock;
@@ -212,6 +227,9 @@ msi_assign_cpu(struct intsrc *isrc, u_in
if (msi->msi_first != msi)
return (EINVAL);
+ if (msix_disable_migration && msi->msi_msix)
+ return (EINVAL);
+
/* Store information to free existing irq. */
old_vector = msi->msi_vector;
old_id = msi->msi_cpu;
@@ -284,6 +302,11 @@ 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: stable/10/sys/x86/xen/hvm.c
==============================================================================
--- stable/10/sys/x86/xen/hvm.c Fri Aug 5 16:53:24 2016 (r303775)
+++ stable/10/sys/x86/xen/hvm.c Fri Aug 5 17:13:25 2016 (r303776)
@@ -385,9 +385,29 @@ xen_hvm_init_hypercall_stubs(void)
return (ENXIO);
if (hypercall_stubs == NULL) {
+ 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;
+ }
}
/*
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