Messages in this thread | | | From | Penttilä Mika <> | Subject | RE: [PATCH] x86_64: do not assume head_64.S used 4KB pages when !use_pse | Date | Thu, 23 Jun 2011 16:25:34 +0000 |
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> From: Stefano Stabellini [mailto:stefano.stabellini@eu.citrix.com] > Sent: 23. kesäkuuta 2011 18:20 > To: Penttilä Mika > Cc: Stefano Stabellini; linux-kernel@vger.kernel.org > Subject: RE: [PATCH] x86_64: do not assume head_64.S used 4KB pages > when !use_pse > > On Thu, 23 Jun 2011, Penttilä Mika wrote: > > > > And arch/x86/mm/init.c also has: > > > > > > > > #if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_KMEMCHECK) > > > > /* > > > > * For CONFIG_DEBUG_PAGEALLOC, identity mapping will use > > > small pages. > > > > * This will simplify cpa(), which otherwise needs to > support > > > splitting > > > > * large pages into small in interrupt context, etc. > > > > */ > > > > use_pse = use_gbpages = 0; > > > > #else > > > > use_pse = cpu_has_pse; > > > > use_gbpages = direct_gbpages; > > > > #endif > > > > > > > > > > > > So big pages are also not used for DEBUG_PAGEALLOC and KMEMCHECK > > > configs even if head_32.S did. > > > > > > Right, but that is not a problem because head_32.S always uses 4KB > > > pages. > > > > We use large pages FOR PAE kernels on x86-32 there > > > > Do you mean we use large pages for PAE kernels on x86_32 in > arch/x86/mm/init.c:init_memory_mapping? > That wouldn't be a problem for this patch. > > The problem I am trying to solve occurs when head_64.S doesn't allocate > any pte pages because it is using 2MB pages, while init_memory_mapping > wants to use 4KB pages (for example because the user set > CONFIG_DEBUG_PAGEALLOC). > > So on x86_32 is not going to be an issue because head_32.S doesn't use > 2MB or 4MB pages as far as I can tell, even if the hardware supports > them. > Please correct me if I am wrong but I don't see any _PAGE_PSE in > head_32.S.
Yes you're right head_32.S doesn't do large pages, I remembered it would..
--Mika
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