Messages in this thread | | | Date | Thu, 28 Sep 2017 16:31:12 +0800 | From | Baoquan He <> | Subject | Re: [PATCH v2 RESEND 2/2] x86/mm/KASLR: Do not adapt the size of the direct mapping section for SGI UV system |
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Hi Ingo,
On 09/28/17 at 09:56am, Ingo Molnar wrote: > > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > > index af599167fe3c..4d68c08df82d 100644 > > --- a/arch/x86/mm/kaslr.c > > +++ b/arch/x86/mm/kaslr.c > > @@ -27,6 +27,7 @@ > > #include <asm/pgtable.h> > > #include <asm/setup.h> > > #include <asm/kaslr.h> > > +#include <asm/uv/uv.h> > > > > #include "mm_internal.h" > > > > @@ -123,7 +124,7 @@ void __init kernel_randomize_memory(void) > > CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING; > > > > /* Adapt phyiscal memory region size based on available memory */ > > - if (memory_tb < kaslr_regions[0].size_tb) > > + if (memory_tb < kaslr_regions[0].size_tb && !is_early_uv_system()) > > kaslr_regions[0].size_tb = memory_tb; > This is really an ugly hack. Is kaslr_regions[] incorrect? If so then it should be > corrected instead of uglifying the code that uses it...
Thanks for looking into this!
If on SGI UV system, the kaslr_regions[0].size_tb, namely the size of the direct mapping section, is incorrect.
Its direct mapping size includes two parts: #1 RAM size of system #2 MMIOH region size which only SGI UV system has.
However, the #2 can only be got till uv_system_init() is called in native_smp_prepare_cpus(). That is too late for mm KASLR calculation. That's why I made this hack.
I checked uv_system_init() code, seems not easy to know the size of MMIOH region before or inside kernel_randomize_memory(). I have CCed UV devel experts, not sure if they have any idea about this. Otherwise, this patch could be the only way I can think of.
Hi Mike and Russ,
Is there any chance we can get the size of MMIOH region before mm KASLR code, namely before we call kernel_randomize_memory()?
Thanks Baoquan
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