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Message-ID: <a2791312-2957-27e6-43af-c805bbb90266@collabora.com>
Date: Tue, 15 Mar 2022 01:37:19 +0300
From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
To: "Maciej W. Rozycki" <macro@...am.me.uk>,
Nikolai Zhubr <zhubr.2@...il.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>
Cc: Arnd Bergmann <arnd@...nel.org>,
Michal Necasek <mnecasek@...oo.com>, x86@...nel.org,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] x86/PCI: Add $IRT PIRQ routing table support
On 1/6/22 14:24, Maciej W. Rozycki wrote:
> Handle the $IRT PCI IRQ Routing Table format used by AMI for its BCP
> (BIOS Configuration Program) external tool meant for tweaking BIOS
> structures without the need to rebuild it from sources[1].
>
> The $IRT format has been invented by AMI before Microsoft has come up
> with its $PIR format and a $IRT table is therefore there in some systems
> that lack a $PIR table, such as the DataExpert EXP8449 mainboard based
> on the ALi FinALi 486 chipset (M1489/M1487), which predates DMI 2.0 and
> cannot therefore be easily identified at run time.
>
> Unlike with the $PIR format there is no alignment guarantee as to the
> placement of the $IRT table, so scan the whole BIOS area bytewise.
>
> Credit to Michal Necasek for helping me chase documentation for the
> format.
>
> References:
>
> [1] "What is BCP? - AMI", <https://www.ami.com/what-is-bcp/>
>
> Signed-off-by: Maciej W. Rozycki <macro@...am.me.uk>
> Cc: Michal Necasek <mnecasek@...oo.com>
> ---
> New change in v3.
> ---
> arch/x86/include/asm/pci_x86.h | 9 +++++
> arch/x86/pci/irq.c | 71 +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 80 insertions(+)
>
> linux-x86-pirq-irt.diff
> Index: linux-macro/arch/x86/include/asm/pci_x86.h
> ===================================================================
> --- linux-macro.orig/arch/x86/include/asm/pci_x86.h
> +++ linux-macro/arch/x86/include/asm/pci_x86.h
> @@ -90,6 +90,15 @@ struct irq_routing_table {
> struct irq_info slots[0];
> } __attribute__((packed));
>
> +struct irt_routing_table {
> + u32 signature; /* IRT_SIGNATURE should be here */
> + u8 size; /* Number of entries provided */
> + u8 used; /* Number of entries actually used */
> + u16 exclusive_irqs; /* IRQs devoted exclusively to
> + PCI usage */
> + struct irq_info slots[0];
> +} __attribute__((packed));
> +
> extern unsigned int pcibios_irq_mask;
>
> extern raw_spinlock_t pci_config_lock;
> Index: linux-macro/arch/x86/pci/irq.c
> ===================================================================
> --- linux-macro.orig/arch/x86/pci/irq.c
> +++ linux-macro/arch/x86/pci/irq.c
> @@ -25,6 +25,8 @@
> #define PIRQ_SIGNATURE (('$' << 0) + ('P' << 8) + ('I' << 16) + ('R' << 24))
> #define PIRQ_VERSION 0x0100
>
> +#define IRT_SIGNATURE (('$' << 0) + ('I' << 8) + ('R' << 16) + ('T' << 24))
> +
> static int broken_hp_bios_irq9;
> static int acer_tm360_irqrouting;
>
> @@ -91,7 +93,69 @@ static inline struct irq_routing_table *
> return NULL;
> }
>
> +/*
> + * Handle the $IRT PCI IRQ Routing Table format used by AMI for its BCP
> + * (BIOS Configuration Program) external tool meant for tweaking BIOS
> + * structures without the need to rebuild it from sources. The $IRT
> + * format has been invented by AMI before Microsoft has come up with its
> + * $PIR format and a $IRT table is therefore there in some systems that
> + * lack a $PIR table.
> + *
> + * It uses the same PCI BIOS 2.1 format for interrupt routing entries
> + * themselves but has a different simpler header prepended instead,
> + * occupying 8 bytes, where a `$IRT' signature is followed by one byte
> + * specifying the total number of interrupt routing entries allocated in
> + * the table, then one byte specifying the actual number of entries used
> + * (which the BCP tool can take advantage of when modifying the table),
> + * and finally a 16-bit word giving the IRQs devoted exclusively to PCI.
> + * Unlike with the $PIR table there is no alignment guarantee.
> + *
> + * Given the similarity of the two formats the $IRT one is trivial to
> + * convert to the $PIR one, which we do here, except that obviously we
> + * have no information as to the router device to use, but we can handle
> + * it by matching PCI device IDs actually seen on the bus against ones
> + * that our individual routers recognise.
> + *
> + * Reportedly there is another $IRT table format where a 16-bit word
> + * follows the header instead that points to interrupt routing entries
> + * in a $PIR table provided elsewhere. In that case this code will not
> + * be reached though as the $PIR table will have been chosen instead.
> + */
> +static inline struct irq_routing_table *pirq_convert_irt_table(u8 *addr)
> +{
> + struct irt_routing_table *ir;
> + struct irq_routing_table *rt;
> + u16 size;
> + u8 sum;
> + int i;
> +
> + ir = (struct irt_routing_table *)addr;
> + if (ir->signature != IRT_SIGNATURE || !ir->used || ir->size < ir->used)
> + return NULL;
>
> + DBG(KERN_DEBUG "PCI: $IRT Interrupt Routing Table found at 0x%lx\n",
> + __pa(ir));
> +
> + size = sizeof(*rt) + ir->used * sizeof(rt->slots[0]);
> + rt = kzalloc(size, GFP_KERNEL);
> + if (!rt)
> + return NULL;
> +
> + rt->signature = PIRQ_SIGNATURE;
> + rt->version = PIRQ_VERSION;
> + rt->size = size;
> + rt->exclusive_irqs = ir->exclusive_irqs;
> + for (i = 0; i < ir->used; i++)
> + rt->slots[i] = ir->slots[i];
> +
> + addr = (u8 *)rt;
> + sum = 0;
> + for (i = 0; i < size; i++)
> + sum += addr[i];
> + rt->checksum = -sum;
> +
> + return rt;
> +}
>
> /*
> * Search 0xf0000 -- 0xfffff for the PCI IRQ Routing Table.
> @@ -113,6 +177,13 @@ static struct irq_routing_table * __init
> if (rt)
> return rt;
> }
> + for (addr = (u8 *)__va(0xf0000);
> + addr < (u8 *)__va(0x100000);
> + addr++) {
> + rt = pirq_convert_irt_table(addr);
> + if (rt)
> + return rt;
> + }
> return NULL;
> }
>
Hi,
This patch broke crosvm using recent linux-next. The "ir = (struct
irt_routing_table *)addr;" contains invalid pointer. Any ideas why?
PCI: Probing PCI hardware
BUG: unable to handle page fault for address: ffffed1000020000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 12fff4067 P4D 12fff4067 PUD 12fff3067 PMD 12fff2067 PTE 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc7-next-20220310+ #226
Hardware name: ChromiumOS crosvm, BIOS 0
RIP: 0010:kasan_check_range+0xe6/0x1a0
Code: 00 74 ee 48 89 c2 b8 01 00 00 00 48 85 d2 75 5d 5b 41 5c 41 5d 5d
c3 48 85 d2 74 63 4c 01 e2 eb 09 48 83 c0 01 48 39 d0 74 55 <80> 38 00
74 f2 eb d2 41 bd 08 00 00 00 45 29 dd 4b 8d 54 25 00 eb
RSP: 0000:ffff8881002c7d98 EFLAGS: 00010297
RAX: ffffed1000020000 RBX: ffffed1000020001 RCX: ffffffff8440db66
RDX: ffffed1000020001 RSI: 0000000000000004 RDI: ffff8880000ffffd
RBP: ffff8881002c7db0 R08: 0000000000000000 R09: ffff888000100000
R10: ffffed1000020000 R11: 0000000000000001 R12: ffffed100001ffff
R13: ffff888000100000 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88810b200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffed1000020000 CR3: 0000000003a29001 CR4: 0000000000170ef0
Call Trace:
<TASK>
__asan_loadN+0xf/0x20
pcibios_irq_init+0xd7/0x484
? pci_legacy_init+0x3b/0x3b
pci_subsys_init+0x88/0x92
do_one_initcall+0xba/0x3e0
? trace_event_raw_event_initcall_level+0x140/0x140
? rcu_read_lock_sched_held+0x46/0x80
kernel_init_freeable+0x33c/0x395
? rest_init+0x280/0x280
kernel_init+0x1e/0x130
ret_from_fork+0x1f/0x30
</TASK>
Modules linked in:
CR2: ffffed1000020000
---[ end trace 0000000000000000 ]---
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