Hi Mike, Russ and Frank, On 09/28/17 at 07:10am, Mike Travis wrote: > > > On 9/28/2017 2:01 AM, Ingo Molnar wrote: > > > > * Baoquan He <b...@redhat.com> wrote: > > > > > > > @@ -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()? > > The sizes of the MMIOL and MMIOH areas are tied into the HUB design and how > it is communicated to BIOS and the kernel. This is via some of the config > MMR's found in the HUB and it would be impossible to provide any access to > these registers as they change with each new UV architecture. > > The kernel does reserve the memory in the EFI memmap. I can send you a > console log of the full startup that includes the MMIOH reservations. Note > that it is dependent on what I/O devices are actually present as UV does not > map empty slots unless forced (because we'd quickly run out of resources.) > Also, the EFI memmap entries do not specify the exact usage of the contained > areas.
This one is still a regression bug in our newer rhel since I just fixed them with rhel-only patch. Now I still need the console log which includes the MMIOH reservations. Could you help provide a console log with MMIOH info, or I need request one from redhat's lab? Or expert from HPE UV team can make a patch based on the finding and analysis? Thanks Baoquan > > > > > I don't mind system specific quirks to hardware enumeration details, as > > long as > > they don't pollute generic code with such special hacks. > > > > I.e. in this case it's wrong to allow kaslr_regions[0].size_tb to be wrong. > > Any > > other code that relies on it in the future will be wrong as well on UV > > systems. > > Which may come into play on other arches with the new upcoming memory > technologies. > > > > The right quirk would be to fix that up where it gets introduced, or > > something > > like that. > > Yes, does make sense. > > > > Thanks, > > > > Ingo > >
