On 2/15/2016 7:26 PM, Rafael J. Wysocki wrote:

On Mon, Feb 15, 2016 at 5:41 PM, Sinan Kaya [off-list ref] wrote:

quoted

A crash has been observed when assigning penalty on x86 systems.

It looks like this problem happens on x86 platforms with IOAPIC and an SCI
interrupt override in the ACPI table with interrupt number greater than
16. (22 in this example)

The bug has been introduced by "ACPI, PCI, irq: remove interrupt count
restriction" commit. The code was using kmalloc to resize the interrupt
list. In this use case, the set penalty call is coming from early phase
and the heap is not initialized yet.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
IP: [<ffffffff811e8b9d>] kmem_cache_alloc_trace+0xad/0x1c0
PGD 0
Oops: 0000 [#1] SMP
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 4.5.0-rc2Feb-3_RK #1
Hardware name: HP Superdome2 16s, BIOS Bundle: 007.006.000 SFW: 033.162.000
10/30/2015
[<ffffffff813bc190>] acpi_irq_set_penalty+0x60/0x8e
[<ffffffff813bc1df>] acpi_irq_add_penalty+0x21/0x26
[<ffffffff813bc76d>] acpi_penalize_sci_irq+0x25/0x28
[<ffffffff81b8260d>] acpi_sci_ioapic_setup+0x68/0x78
[<ffffffff81b830fc>] acpi_boot_init+0x2cc/0x533
[<ffffffff810677c8>] ? set_pte_vaddr_pud+0x48/0x50
[<ffffffff81b828cf>] ? acpi_parse_x2apic+0x77/0x77
[<ffffffff81b82858>] ? dmi_ignore_irq0_timer_override+0x30/0x30
[<ffffffff81b77c1e>] setup_arch+0xc24/0xce9
[<ffffffff81b6e120>] ? early_idt_handler_array+0x120/0x120
[<ffffffff81b6ed94>] start_kernel+0xfc/0x506
[<ffffffff81b6e120>] ? early_idt_handler_array+0x120/0x120
[<ffffffff81b6e120>] ? early_idt_handler_array+0x120/0x120
[<ffffffff81b6e5ee>] x86_64_start_reservations+0x2a/0x2c
[<ffffffff81b6e73c>] x86_64_start_kernel+0x14c/0x16f

Besides from the use case above, there is one more situation where
set_penalty is being called from the init context like. There is support
for setting the penalty through kernel command line.

Adding support to be called from early context for limited number of
interrupts.

Signed-off-by: Sinan Kaya <redacted>

This looks somewhat hackish to me to be honest.

I know.

This is the reason why I wanted to discuss this patch on the list. I hate the
fact that I broke something unintentionally (who would think that kzalloc
 wouldn't work). I'm trying to restore the functionality and I don't like
what I see with the early_memxxx family of functions. 

They all require a fixed size memory allocation from the system memory. Not a
general purpose early_kzalloc function for instance.

quoted

---
 drivers/acpi/pci_link.c | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
index fa28635..24b69e1 100644
--- a/drivers/acpi/pci_link.c
+++ b/drivers/acpi/pci_link.c

@@ -47,6 +47,7 @@ ACPI_MODULE_NAME("pci_link");
 #define ACPI_PCI_LINK_FILE_INFO                "info"
 #define ACPI_PCI_LINK_FILE_STATUS      "state"
 #define ACPI_PCI_LINK_MAX_POSSIBLE     16
+#define ACPI_PCI_LINK_MAX_EARLY_IRQINFO 1024

 static int acpi_pci_link_add(struct acpi_device *device,
                             const struct acpi_device_id *not_used);

@@ -470,9 +471,13 @@ struct irq_penalty_info {
        int irq;
        int penalty;
        struct list_head node;
+       bool early;

Where is this field used ->

got rid of it.

quoted

 };

 static LIST_HEAD(acpi_irq_penalty_list);
+static int early_init_done;
+static struct irq_penalty_info early_irq_infos[ACPI_PCI_LINK_MAX_EARLY_IRQINFO];
+static int early_irq_info_counter;

 static int acpi_irq_get_penalty(int irq)
 {

@@ -507,10 +512,20 @@ static int acpi_irq_set_penalty(int irq, int new_penalty)
                }
        }

-       /* nope, let's allocate a slot for this IRQ */
-       irq_info = kzalloc(sizeof(*irq_info), GFP_KERNEL);
-       if (!irq_info)
-               return -ENOMEM;
+       if (!early_init_done) {
+               if (early_irq_info_counter < ARRAY_SIZE(early_irq_infos)) {
+                       irq_info = &early_irq_infos[early_irq_info_counter];
+                       irq_info->early = true;

-> except for being set here?

thanks, removed.

quoted

+                       early_irq_info_counter++;
+               } else {
+                       return -ENOMEM;
+               }
+       } else {
+               /* nope, let's allocate a slot for this IRQ */
+               irq_info = kzalloc(sizeof(*irq_info), GFP_KERNEL);
+               if (!irq_info)
+                       return -ENOMEM;
+       }

        irq_info->irq = irq;
        irq_info->penalty = new_penalty;

@@ -968,3 +983,12 @@ void __init acpi_pci_link_init(void)
        register_syscore_ops(&irqrouter_syscore_ops);
        acpi_scan_add_handler(&pci_link_handler);
 }
+
+
+static int acpi_pci_link_subsys_init(void)
+{
+       early_init_done = true;

Why do you need yet another subsys_initcall do set this?  Can't it be
set in, say, acpi_init()?

And isn't there any existing way to check that?  Like checking
acpi_gbl_permanent_mmap or something?

I'll use acpi_gbl_permanent_mmap.

quoted

+       return 0;
+}
+
+subsys_initcall(acpi_pci_link_subsys_init)
--

Thanks,
Rafael
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-- 
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project