[tip:x86/urgent] x86/paravirt: Prevent rtc_cmos platform device init on PV guests
From: tip-bot for David Vrabel
Date: Sat Dec 19 2015 - 15:40:01 EST
Commit-ID: d8c98a1d1488747625ad6044d423406e17e99b7a
Gitweb: http://git.kernel.org/tip/d8c98a1d1488747625ad6044d423406e17e99b7a
Author: David Vrabel <david.vrabel@xxxxxxxxxx>
AuthorDate: Fri, 11 Dec 2015 09:07:53 -0500
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Sat, 19 Dec 2015 21:35:13 +0100
x86/paravirt: Prevent rtc_cmos platform device init on PV guests
Adding the rtc platform device in non-privileged Xen PV guests causes
an IRQ conflict because these guests do not have legacy PIC and may
allocate irqs in the legacy range.
In a single VCPU Xen PV guest we should have:
/proc/interrupts:
CPU0
0: 4934 xen-percpu-virq timer0
1: 0 xen-percpu-ipi spinlock0
2: 0 xen-percpu-ipi resched0
3: 0 xen-percpu-ipi callfunc0
4: 0 xen-percpu-virq debug0
5: 0 xen-percpu-ipi callfuncsingle0
6: 0 xen-percpu-ipi irqwork0
7: 321 xen-dyn-event xenbus
8: 90 xen-dyn-event hvc_console
...
But hvc_console cannot get its interrupt because it is already in use
by rtc0 and the console does not work.
genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 (rtc0)
We can avoid this problem by realizing that unprivileged PV guests (both
Xen and lguests) are not supposed to have rtc_cmos device and so
adding it is not necessary.
Privileged guests (i.e. Xen's dom0) do use it but they should not have
irq conflicts since they allocate irqs above legacy range (above
gsi_top, in fact).
Instead of explicitly testing whether the guest is privileged we can
extend pv_info structure to include information about guest's RTC
support.
Reported-and-tested-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: vkuznets@xxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: konrad.wilk@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # 4.2+
Link: http://lkml.kernel.org/r/1449842873-2613-1-git-send-email-boris.ostrovsky@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
arch/x86/include/asm/paravirt.h | 6 ++++++
arch/x86/include/asm/paravirt_types.h | 5 +++++
arch/x86/include/asm/processor.h | 1 +
arch/x86/kernel/rtc.c | 3 +++
arch/x86/lguest/boot.c | 1 +
arch/x86/xen/enlighten.c | 4 +++-
6 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 10d0596..c759b3c 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -19,6 +19,12 @@ static inline int paravirt_enabled(void)
return pv_info.paravirt_enabled;
}
+static inline int paravirt_has_feature(unsigned int feature)
+{
+ WARN_ON_ONCE(!pv_info.paravirt_enabled);
+ return (pv_info.features & feature);
+}
+
static inline void load_sp0(struct tss_struct *tss,
struct thread_struct *thread)
{
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 31247b5..3d44191 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -70,9 +70,14 @@ struct pv_info {
#endif
int paravirt_enabled;
+ unsigned int features; /* valid only if paravirt_enabled is set */
const char *name;
};
+#define paravirt_has(x) paravirt_has_feature(PV_SUPPORTED_##x)
+/* Supported features */
+#define PV_SUPPORTED_RTC (1<<0)
+
struct pv_init_ops {
/*
* Patch may replace one of the defined code sequences with
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 6752225..2d5a50c 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -472,6 +472,7 @@ static inline unsigned long current_top_of_stack(void)
#else
#define __cpuid native_cpuid
#define paravirt_enabled() 0
+#define paravirt_has(x) 0
static inline void load_sp0(struct tss_struct *tss,
struct thread_struct *thread)
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index cd96852..4af8d06 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -200,6 +200,9 @@ static __init int add_rtc_cmos(void)
}
#endif
+ if (paravirt_enabled() && !paravirt_has(RTC))
+ return -ENODEV;
+
platform_device_register(&rtc_device);
dev_info(&rtc_device.dev,
"registered platform RTC device (no PNP device found)\n");
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index a0d09f6..a43b2ea 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1414,6 +1414,7 @@ __init void lguest_init(void)
pv_info.kernel_rpl = 1;
/* Everyone except Xen runs with this set. */
pv_info.shared_kernel_pmd = 1;
+ pv_info.features = 0;
/*
* We set up all the lguest overrides for sensitive operations. These
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index d315151..b7de78b 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1192,7 +1192,7 @@ static const struct pv_info xen_info __initconst = {
#ifdef CONFIG_X86_64
.extra_user_64bit_cs = FLAT_USER_CS64,
#endif
-
+ .features = 0,
.name = "Xen",
};
@@ -1535,6 +1535,8 @@ asmlinkage __visible void __init xen_start_kernel(void)
/* Install Xen paravirt ops */
pv_info = xen_info;
+ if (xen_initial_domain())
+ pv_info.features |= PV_SUPPORTED_RTC;
pv_init_ops = xen_init_ops;
pv_apic_ops = xen_apic_ops;
if (!xen_pvh_domain()) {
--
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