Re: [PATCH 4.4 50/62] XEN uses irqdesc::irq_data_common::handler_data to store a per interrupt XEN data pointer which contains XEN specific information.

[Stefan Bader <stefan.bader@canonical.com>]

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On 29.09.20 16:05, Jürgen Groß wrote:
> On 29.09.20 15:13, Stefan Bader wrote:
>> On 01.09.20 17:10, Greg Kroah-Hartman wrote:
>>> From: Thomas Gleixner <tglx@linutronix.de>
>>>
>>> commit c330fb1ddc0a922f044989492b7fcca77ee1db46 upstream.
>>>
>>> handler data is meant for interrupt handlers and not for storing irq chip
>>> specific information as some devices require handler data to store internal
>>> per interrupt information, e.g. pinctrl/GPIO chained interrupt handlers.
>>>
>>> This obviously creates a conflict of interests and crashes the machine
>>> because the XEN pointer is overwritten by the driver pointer.
>>
>> I cannot say whether this applies the same for the vanilla 4.4 stable kernels
>> but once this had been applied to our 4.4 based kernels, we observed Xen HVM
>> guests crashing on boot with:
>>
>> [    0.927538] ACPI: bus type PCI registered
>> [    0.936008] acpiphp: ACPI Hot Plug PCI Controller Driver version: 0.5
>> [    0.948739] PCI: Using configuration type 1 for base access
>> [    0.960007] PCI: Using configuration type 1 for extended access
>> [    0.984340] ACPI: Added _OSI(Module Device)
>> [    0.988010] ACPI: Added _OSI(Processor Device)
>> [    0.992007] ACPI: Added _OSI(3.0 _SCP Extensions)
>> [    0.996013] ACPI: Added _OSI(Processor Aggregator Device)
>> [    1.002103] BUG: unable to handle kernel paging request at ffffffffff5f3000
>> [    1.004000] IP: [<ffffffff810592ff>] mp_irqdomain_activate+0x5f/0xa0
>> [    1.004000] PGD 1e0f067 PUD 1e11067 PMD 1e12067 PTE 0
>> [    1.004000] Oops: 0002 [#1] SMP
>> [    1.004000] Modules linked in:
>> [    1.004000] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 4.4.0-191-generic
>> #221-Ubuntu
>> [    1.004000] Hardware name: Xen HVM domU, BIOS 4.6.5 04/18/2018
>> [    1.004000] task: ffff880107db0000 ti: ffff880107dac000 task.ti:
>> ffff880107dac000
>> [    1.004000] RIP: 0010:[<ffffffff810592ff>]  [<ffffffff810592ff>]
>> mp_irqdomain_activate+0x5f/0xa0
>> [    1.004000] RSP: 0018:ffff880107dafc48  EFLAGS: 00010086
>> [    1.004000] RAX: 0000000000000086 RBX: ffff8800eb852140 RCX: 0000000000000000
>> [    1.004000] RDX: ffffffffff5f3000 RSI: 0000000000000001 RDI: 000000000020c000
>> [    1.004000] RBP: ffff880107dafc50 R08: ffffffff81ebdfd0 R09: 00000000ffffffff
>> [    1.004000] R10: 0000000000000011 R11: 0000000000000009 R12: ffff88010880d400
>> [    1.004000] R13: 0000000000000001 R14: 0000000000000009 R15: ffff8800eb880080
>> [    1.004000] FS:  0000000000000000(0000) GS:ffff880108ec0000(0000)
>> knlGS:0000000000000000
>> [    1.004000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [    1.004000] CR2: ffffffffff5f3000 CR3: 0000000001e0a000 CR4: 00000000000006f0
>> [    1.004000] Stack:
>> [    1.004000]  ffff88010880bc58 ffff880107dafc70 ffffffff810ea644
>> ffff88010880bc00
>> [    1.004000]  ffff88010880bc58 ffff880107dafca0 ffffffff810e6d88
>> ffffffff810e1009
>> [    1.004000]  ffff88010880bc00 ffff88010880bca0 ffff8800eb880080
>> ffff880107dafd38
>> [    1.004000] Call Trace:
>> [    1.004000]  [<ffffffff810ea644>] irq_domain_activate_irq+0x44/0x50
>> [    1.004000]  [<ffffffff810e6d88>] irq_startup+0x38/0x90
>> [    1.004000]  [<ffffffff810e1009>] ? vprintk_default+0x29/0x40
>> [    1.004000]  [<ffffffff810e55e2>] __setup_irq+0x5a2/0x650
>> [    1.004000]  [<ffffffff811fc064>] ? kmem_cache_alloc_trace+0x1d4/0x1f0
>> [    1.004000]  [<ffffffff814a3870>] ? acpi_osi_handler+0xb0/0xb0
>> [    1.004000]  [<ffffffff810e582b>] request_threaded_irq+0xfb/0x1a0
>> [    1.004000]  [<ffffffff814a3870>] ? acpi_osi_handler+0xb0/0xb0
>> [    1.004000]  [<ffffffff814bf624>] ? acpi_ev_sci_dispatch+0x64/0x64
>> [    1.004000]  [<ffffffff814a3f0a>] acpi_os_install_interrupt_handler+0xaa/0x100
>> [    1.004000]  [<ffffffff81fb26e1>] ? acpi_sleep_proc_init+0x28/0x28
>> [    1.004000]  [<ffffffff814bf689>] acpi_ev_install_sci_handler+0x23/0x25
>> [    1.004000]  [<ffffffff814bcf03>] acpi_ev_install_xrupt_handlers+0x1c/0x6c
>> [    1.004000]  [<ffffffff81fb3e9d>] acpi_enable_subsystem+0x8f/0x93
>> [    1.004000]  [<ffffffff81fb276c>] acpi_init+0x8b/0x2c4
>> [    1.004000]  [<ffffffff8141ee1e>] ? kasprintf+0x4e/0x70
>> [    1.004000]  [<ffffffff81fb26e1>] ? acpi_sleep_proc_init+0x28/0x28
>> [    1.004000]  [<ffffffff810021f5>] do_one_initcall+0xb5/0x200
>> [    1.004000]  [<ffffffff810a6fda>] ? parse_args+0x29a/0x4a0
>> [    1.004000]  [<ffffffff81f69152>] kernel_init_freeable+0x177/0x218
>> [    1.004000]  [<ffffffff8185dcf0>] ? rest_init+0x80/0x80
>> [    1.004000]  [<ffffffff8185dcfe>] kernel_init+0xe/0xe0
>> [    1.004000]  [<ffffffff8186ae92>] ret_from_fork+0x42/0x80
>> [    1.004000]  [<ffffffff8185dcf0>] ? rest_init+0x80/0x80
>> [    1.004000] Code: 8d 1c d2 8d ba 0b 02 00 00 44 8d 51 11 42 8b 14 dd 74 ec 10
>> 82 c1 e7 0c 48 63 ff 81 e2 ff 0f 00 00 48 81 ea 00 10 80 00 48 29 fa <44> 89 12
>> 89 72 10 42 8b 14 dd 74 ec 10 82 83 c1 10 81 e2 ff 0f
>> [    1.004000] RIP  [<ffffffff810592ff>] mp_irqdomain_activate+0x5f/0xa0
>> [    1.004000]  RSP <ffff880107dafc48>
>> [    1.004000] CR2: ffffffffff5f3000
>> [    1.004000] ---[ end trace 3201cae5b6bd7be1 ]---
>> [    1.592027] Kernel panic - not syncing: Attempted to kill init!
>> exitcode=0x00000009
>> [    1.592027]
>>
>> This is from a local server but same stack-trace happens on AWS instances while
>> initializing ACPI SCI. mp_irqdomain_activate is accessing chip_data expecting
>> ioapic data there. Oddly enough more recent kernels seem to do the same but not
>> crashing as HVM guest (neither seen for our 4.15 nor the 5.4).
> 
> Hmm, could it be that calling irq_set_chip_data() for a legacy irq is
> a rather bad idea?
> 
> Could you please try the attached patch (might need some backport, but
> should be rather easy)?

Ok, I can confirm that adding your patch (minor backport to 4.4 attached) on top
of the change to use chip_data generally, the HVM guest does come up
successfully. Again, I was unable to figure out why this fixup is not needed in
more recent kernels, but for 4.4.y it seems to be needed.

Thanks,
Stefan

> 
> 
> Juergen


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From b7a74e75bbee9b70ec0b281d0399e9c6c25bd610 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Tue, 29 Sep 2020 15:47:21 +0200
Subject: [PATCH] xen/events: don't use chip_data for legacy IRQs

Storing Xen specific data via chip_data is fine, as long as this isn't
done for a legacy IRQ.

Use a local array for this purpose in case of legacy IRQs.

Signed-off-by: Juergen Gross <jgross@suse.com>
[smb: backport adjust context around __unbind_from_irq]
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
---
 drivers/xen/events/events_base.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index e4dd991e2888..9a126732d5d9 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -91,6 +91,8 @@ static bool (*pirq_needs_eoi)(unsigned irq);
 /* Xen will never allocate port zero for any purpose. */
 #define VALID_EVTCHN(chn)	((chn) != 0)
 
+static struct irq_info *legacy_info_ptrs[NR_IRQS_LEGACY];
+
 static struct irq_chip xen_dynamic_chip;
 static struct irq_chip xen_percpu_chip;
 static struct irq_chip xen_pirq_chip;
@@ -155,7 +157,18 @@ int get_evtchn_to_irq(unsigned evtchn)
 /* Get info for IRQ */
 struct irq_info *info_for_irq(unsigned irq)
 {
-	return irq_get_chip_data(irq);
+	if (irq < nr_legacy_irqs())
+		return legacy_info_ptrs[irq];
+	else
+		return irq_get_chip_data(irq);
+}
+
+static void set_info_for_irq(unsigned int irq, struct irq_info *info)
+{
+	if (irq < nr_legacy_irqs())
+		legacy_info_ptrs[irq] = info;
+	else
+		irq_set_chip_data(irq, info);
 }
 
 /* Constructors for packed IRQ information. */
@@ -384,7 +397,7 @@ static void xen_irq_init(unsigned irq)
 	info->type = IRQT_UNBOUND;
 	info->refcnt = -1;
 
-	irq_set_chip_data(irq, info);
+	set_info_for_irq(irq, info);
 
 	list_add_tail(&info->list, &xen_irq_list_head);
 }
@@ -433,14 +446,14 @@ static int __must_check xen_allocate_irq_gsi(unsigned gsi)
 
 static void xen_free_irq(unsigned irq)
 {
-	struct irq_info *info = irq_get_chip_data(irq);
+	struct irq_info *info = info_for_irq(irq);
 
 	if (WARN_ON(!info))
 		return;
 
 	list_del(&info->list);
 
-	irq_set_chip_data(irq, NULL);
+	set_info_for_irq(irq, NULL);
 
 	WARN_ON(info->refcnt > 0);
 
@@ -610,7 +623,7 @@ EXPORT_SYMBOL_GPL(xen_irq_from_gsi);
 static void __unbind_from_irq(unsigned int irq)
 {
 	int evtchn = evtchn_from_irq(irq);
-	struct irq_info *info = irq_get_chip_data(irq);
+	struct irq_info *info = info_for_irq(irq);
 
 	if (info->refcnt > 0) {
 		info->refcnt--;
@@ -1114,7 +1127,7 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
 
 void unbind_from_irqhandler(unsigned int irq, void *dev_id)
 {
-	struct irq_info *info = irq_get_chip_data(irq);
+	struct irq_info *info = info_for_irq(irq);
 
 	if (WARN_ON(!info))
 		return;
@@ -1148,7 +1161,7 @@ int evtchn_make_refcounted(unsigned int evtchn)
 	if (irq == -1)
 		return -ENOENT;
 
-	info = irq_get_chip_data(irq);
+	info = info_for_irq(irq);
 
 	if (!info)
 		return -ENOENT;
@@ -1176,7 +1189,7 @@ int evtchn_get(unsigned int evtchn)
 	if (irq == -1)
 		goto done;
 
-	info = irq_get_chip_data(irq);
+	info = info_for_irq(irq);
 
 	if (!info)
 		goto done;
-- 
2.25.1


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