Messages in this thread Patch in this message | | | Subject | [PATCH] Fix VMI crash on boot in 2.6.27+ kernels | From | Zachary Amsden <> | Date | Tue, 09 Dec 2008 16:50:21 -0800 |
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Patches backported into 2.6.27.4 caused a regression with VMI kernels running on VMware which ends in a page fault during boot. I have a fix which still allows DMI checks to be done early.
VMI initialiation can relocate the fixmap, causing early_ioremap to malfunction if it is initialized before the relocation. The ioremap area is low enough in virtual address space that no actual collision occurs, however, because the pagetables for it were not allocated under VMI mode, the pagetable updates are dropped by the hypervisor as irrelevant, resulting in a crash on boot.
The best fix is perhaps to move early_ioremap_init() after vmi_init(). The only things done before VMI init are basic memory access, things like collating the memory map, collecting boot CPUID capabilities, and parsing the early command line options... which vmi_init needs.
Since this went back into 2.6.27, it needs to go to both 2.6.28 and eventually to stable. I didn't add any comments or anything as there could be some debate what the proper ordering should be. In case that becomes an interesting discussion, there are two relevant facts in git today:
1) no clients of early_ioremap occur before DMI. 2) VMI requires access to early boot params.
If any can suggest a better ordering, I am certainly open to that as well.
Thanks,
Zach VMI initialiation can relocate the fixmap, causing early_ioremap to malfunction if it is initialized before the relocation. The ioremap area is low enough in virtual address space that no actual collision occurs, however, because the pagetables for it were not allocated under VMI mode, the pagetable updates are dropped by the hypervisor as irrelevant, resulting in a crash on boot.
Signed-off-by: Zachary Amsden <zach@vmware.com>
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 9d5674f..9627753 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -795,7 +795,6 @@ void __init setup_arch(char **cmdline_p) #endif early_cpu_init(); - early_ioremap_init(); ROOT_DEV = old_decode_dev(boot_params.hdr.root_dev); screen_info = boot_params.screen_info; @@ -888,6 +887,8 @@ void __init setup_arch(char **cmdline_p) vmi_init(); #endif + early_ioremap_init(); + /* after early param, so could get panic from serial */ reserve_early_setup_data(); | |