Messages in this thread | | | Date | Thu, 3 Jan 2008 13:29:31 -0500 | From | Vivek Goyal <> | Subject | Re: [PATCH] [1/8] GBPAGES: Handle kernel near memory hole in clear_kernel_mapping |
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On Thu, Jan 03, 2008 at 06:26:57PM +0100, Andi Kleen wrote: > > This was a long standing obscure problem in the relocatable kernel. The > AMD GART driver needs to unmap part of the GART in the kernel direct mapping to > prevent cache corruption. With the relocatable kernel it is in theory possible > that the separate kernel text mapping straddles that area too. > > Normally it should not happen because GART tends to be >= 2GB, and the kernel > is normally not loaded that high, but it is possible in theory. > > Teach clear_kernel_mapping() about this case. > > This will become more important once the kernel mapping uses 1GB pages. > > Cc: ebiederm@xmission.com > Cc: vgoyal@redhat.com > > Signed-off-by: Andi Kleen <ak@suse.de> > > --- > arch/x86/mm/init_64.c | 20 +++++++++++++++++++- > 1 file changed, 19 insertions(+), 1 deletion(-) > > Index: linux/arch/x86/mm/init_64.c > =================================================================== > --- linux.orig/arch/x86/mm/init_64.c > +++ linux/arch/x86/mm/init_64.c > @@ -411,7 +411,8 @@ void __init paging_init(void) > from the CPU leading to inconsistent cache lines. address and size > must be aligned to 2MB boundaries. > Does nothing when the mapping doesn't exist. */ > -void __init clear_kernel_mapping(unsigned long address, unsigned long size) > +static void __init > +__clear_kernel_mapping(unsigned long address, unsigned long size) > { > unsigned long end = address + size; > > @@ -441,6 +442,23 @@ void __init clear_kernel_mapping(unsigne > __flush_tlb_all(); > } > > +#define overlaps(as,ae,bs,be) ((ae) >= (bs) && (as) <= (be)) > + > +void __init clear_kernel_mapping(unsigned long address, unsigned long size) > +{ > + int sh = PMD_SHIFT; > + unsigned long kernel = __pa(__START_KERNEL_map); > + > + if (overlaps(kernel>>sh, (kernel + KERNEL_TEXT_SIZE)>>sh, > + __pa(address)>>sh, __pa(address + size)>>sh)) { > + printk(KERN_INFO > + "Kernel at %lx overlaps memory hole at %lx-%lx\n", > + kernel, __pa(address), __pa(address+size)); > + __clear_kernel_mapping(__START_KERNEL_map+__pa(address), size);
Hi Andi,
Got a question. How will kernel continue to run if we unmap the kernel text/data region mappings?
Thanks Vivek
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