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authorKarimAllah Ahmed <karahmed@amazon.de>2016-08-26 23:55:36 +0200
committerDavid Vrabel <david.vrabel@citrix.com>2016-09-30 11:44:34 +0100
commit72a9b186292d98494f222226cfd24a1621796209 (patch)
tree62bf7896b9e9971a4106adf28dd22b8f3cba4c24 /arch
parentc8761e2016aa51a2829563b02a0a55913bdb0be8 (diff)
xen: Remove event channel notification through Xen PCI platform device
Ever since commit 254d1a3f02eb ("xen/pv-on-hvm kexec: shutdown watches from old kernel") using the INTx interrupt from Xen PCI platform device for event channel notification would just lockup the guest during bootup. postcore_initcall now calls xs_reset_watches which will eventually try to read a value from XenStore and will get stuck on read_reply at XenBus forever since the platform driver is not probed yet and its INTx interrupt handler is not registered yet. That means that the guest can not be notified at this moment of any pending event channels and none of the per-event handlers will ever be invoked (including the XenStore one) and the reply will never be picked up by the kernel. The exact stack where things get stuck during xenbus_init: -xenbus_init -xs_init -xs_reset_watches -xenbus_scanf -xenbus_read -xs_single -xs_single -xs_talkv Vector callbacks have always been the favourite event notification mechanism since their introduction in commit 38e20b07efd5 ("x86/xen: event channels delivery on HVM.") and the vector callback feature has always been advertised for quite some time by Xen that's why INTx was broken for several years now without impacting anyone. Luckily this also means that event channel notification through INTx is basically dead-code which can be safely removed without impacting anybody since it has been effectively disabled for more than 4 years with nobody complaining about it (at least as far as I'm aware of). This commit removes event channel notification through Xen PCI platform device. Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Juergen Gross <jgross@suse.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Cc: Julien Grall <julien.grall@citrix.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Ross Lagerwall <ross.lagerwall@citrix.com> Cc: xen-devel@lists.xenproject.org Cc: linux-kernel@vger.kernel.org Cc: linux-pci@vger.kernel.org Cc: Anthony Liguori <aliguori@amazon.com> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/include/asm/xen/events.h11
-rw-r--r--arch/x86/pci/xen.c2
-rw-r--r--arch/x86/xen/enlighten.c21
-rw-r--r--arch/x86/xen/smp.c2
-rw-r--r--arch/x86/xen/time.c5
5 files changed, 7 insertions, 34 deletions
diff --git a/arch/x86/include/asm/xen/events.h b/arch/x86/include/asm/xen/events.h
index e6911caf5bbf..608a79d5a466 100644
--- a/arch/x86/include/asm/xen/events.h
+++ b/arch/x86/include/asm/xen/events.h
@@ -20,15 +20,4 @@ static inline int xen_irqs_disabled(struct pt_regs *regs)
/* No need for a barrier -- XCHG is a barrier on x86. */
#define xchg_xen_ulong(ptr, val) xchg((ptr), (val))
-extern int xen_have_vector_callback;
-
-/*
- * Events delivered via platform PCI interrupts are always
- * routed to vcpu 0 and hence cannot be rebound.
- */
-static inline bool xen_support_evtchn_rebind(void)
-{
- return (!xen_hvm_domain() || xen_have_vector_callback);
-}
-
#endif /* _ASM_X86_XEN_EVENTS_H */
diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 3a483cb5ac81..bedfab98077a 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -456,7 +456,7 @@ void __init xen_msi_init(void)
int __init pci_xen_hvm_init(void)
{
- if (!xen_have_vector_callback || !xen_feature(XENFEAT_hvm_pirqs))
+ if (!xen_feature(XENFEAT_hvm_pirqs))
return 0;
#ifdef CONFIG_ACPI
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index a9ba14ac3aea..366b6aed4a8e 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -137,8 +137,6 @@ struct shared_info xen_dummy_shared_info;
void *xen_initial_gdt;
RESERVE_BRK(shared_info_page_brk, PAGE_SIZE);
-__read_mostly int xen_have_vector_callback;
-EXPORT_SYMBOL_GPL(xen_have_vector_callback);
static int xen_cpu_up_prepare(unsigned int cpu);
static int xen_cpu_up_online(unsigned int cpu);
@@ -1524,10 +1522,7 @@ static void __init xen_pvh_early_guest_init(void)
if (!xen_feature(XENFEAT_auto_translated_physmap))
return;
- if (!xen_feature(XENFEAT_hvm_callback_vector))
- return;
-
- xen_have_vector_callback = 1;
+ BUG_ON(!xen_feature(XENFEAT_hvm_callback_vector));
xen_pvh_early_cpu_init(0, false);
xen_pvh_set_cr_flags(0);
@@ -1864,9 +1859,7 @@ static int xen_cpu_up_prepare(unsigned int cpu)
xen_vcpu_setup(cpu);
}
- if (xen_pv_domain() ||
- (xen_have_vector_callback &&
- xen_feature(XENFEAT_hvm_safe_pvclock)))
+ if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock))
xen_setup_timer(cpu);
rc = xen_smp_intr_init(cpu);
@@ -1882,9 +1875,7 @@ static int xen_cpu_dead(unsigned int cpu)
{
xen_smp_intr_free(cpu);
- if (xen_pv_domain() ||
- (xen_have_vector_callback &&
- xen_feature(XENFEAT_hvm_safe_pvclock)))
+ if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock))
xen_teardown_timer(cpu);
return 0;
@@ -1922,8 +1913,8 @@ static void __init xen_hvm_guest_init(void)
xen_panic_handler_init();
- if (xen_feature(XENFEAT_hvm_callback_vector))
- xen_have_vector_callback = 1;
+ BUG_ON(!xen_feature(XENFEAT_hvm_callback_vector));
+
xen_hvm_smp_init();
WARN_ON(xen_cpuhp_setup());
xen_unplug_emulated_devices();
@@ -1961,7 +1952,7 @@ bool xen_hvm_need_lapic(void)
return false;
if (!xen_hvm_domain())
return false;
- if (xen_feature(XENFEAT_hvm_pirqs) && xen_have_vector_callback)
+ if (xen_feature(XENFEAT_hvm_pirqs))
return false;
return true;
}
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 137afbbd0590..311acad7dad2 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -765,8 +765,6 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
void __init xen_hvm_smp_init(void)
{
- if (!xen_have_vector_callback)
- return;
smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
smp_ops.cpu_die = xen_cpu_die;
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 67356d29d74d..33d8f6a7829d 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -432,11 +432,6 @@ static void xen_hvm_setup_cpu_clockevents(void)
void __init xen_hvm_init_time_ops(void)
{
- /* vector callback is needed otherwise we cannot receive interrupts
- * on cpu > 0 and at this point we don't know how many cpus are
- * available */
- if (!xen_have_vector_callback)
- return;
if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
printk(KERN_INFO "Xen doesn't support pvclock on HVM,"
"disable pv timer\n");