Re: [PATCH] acpi, pci, irq: account for early penalty assignment

Rafael J. Wysocki
2016-02-16T00:26:49Z

On Mon, Feb 15, 2016 at 5:41 PM, Sinan Kaya <okaya@codeaurora.org> wrote:
> 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 <okaya@codeaurora.org>

This looks somewhat hackish to me to be honest.

> ---
> 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 ->

> };
>
> 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?

> + 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?

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

Thanks,
Rafael