Re: [PATCH] x86: detect use of extended APIC ID for AMD CPUs

Bastian Blank
2009-07-21T10:43:20Z

On Thu, Jun 04, 2009 at 12:40:16PM +0200, Andreas Herrmann wrote:
> Booting a 32-bit kernel on Magny-Cours results in the following panic

This patch breaks Xen really bad. It uses read_pci_config without
knowing that there is something accessible. Also read_pci_config does
not define fault handlers.

| (XEN) traps.c:413:d375 Unhandled general protection fault fault/trap [#13] on VCPU 0 [ec=0000]
| (XEN) domain_crash_sync called from entry.S
| (XEN) Domain 375 (vcpu#0) crashed on cpu#1:
| (XEN) ----[ Xen-3.2-1 x86_64 debug=n Not tainted ]----
| (XEN) CPU: 1
| (XEN) RIP: e033:[<ffffffff80401d6b>]
| (XEN) RFLAGS: 0000000000000282 CONTEXT: guest
| (XEN) rax: 000000008000c068 rbx: ffffffff80618a40 rcx: 0000000000000068
| (XEN) rdx: 0000000000000cf8 rsi: 000000000000c000 rdi: 0000000000000000
| (XEN) rbp: 0000000000000018 rsp: ffffffff80621eb0 r8: ffffffff80621efc
| (XEN) r9: 00000000ffffffff r10: ffffffff80621ef8 r11: 00000000ffffffff
| (XEN) r12: ffffffffffffffff r13: ffffffff80621fd8 r14: 0000002040404030
| (XEN) r15: 00000000015bb600 cr0: 000000008005003b cr4: 00000000000006f0
| (XEN) cr3: 00000002077be000 cr2: 000000204316b000
| (XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 ss: e02b cs: e033
| (XEN) Guest stack trace from rsp=ffffffff80621eb0:
| (XEN) 0000000000000068 00000000ffffffff 0000000000000000 ffffffff80401d6b
| (XEN) 000000010000e030 0000000000010082 ffffffff80621ef0 000000000000e02b
| (XEN) ffffffff804aeb3a 0000000100000000 0000302800000000 ffffffff805bcb20
| (XEN) ffffffff80651552 0000000000000000 0000000000000000 0000000000fdfd88
| (XEN) ffffffff8064e47c 0000000001fb9000 ffffffff80545875 0000000000000800
| (XEN) 0000000000002c00 ffffffff81fb9000 ffffffff80650026 ffffffff805ca1c0

| ffffffff80401d44 T read_pci_config
| ffffffff804aeb41 t early_init_amd

I see several ways to fix this:
- Define fault handlers for *_pci_config
- Check for Xen
- Disable early PCI access from Xen if running unpriviledged and check
that in either in *_pci_config or early_init_amd

Bastian

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