Messages in this thread Patch in this message | | | Date | Tue, 15 Mar 2016 17:03:19 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/mm/pat: Fix boot crash when 1GB pages are not supported by cpu |
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On Mon, Mar 14, 2016 at 10:33:01AM +0000, Matt Fleming wrote: > Scott reports that with the new separate EFI page tables he's seeing > the following error on boot, caused by setting reserved bits in the > page table structures (fault code is PF_RSVD | PF_PROT), > > swapper/0: Corrupted page table at address 17b102020 > PGD 17b0e5063 PUD 1400000e3 > Bad pagetable: 0009 [#1] SMP > > On first inspection the PUD is using a 1GB page size (_PAGE_PSE) and > looks fine but that's only true if support for 1GB PUD pages > ("pdpe1gb") is present in the cpu. > > Scott's Intel Celeron N2820 does not have that feature and so the > _PAGE_PSE bit is reserved. Fix this issue by making the 1GB mapping > code in conditional on "cpu_has_gbpages". > > This issue didn't come up in the past because the required mapping for > the faulting address (0x17b102020) will already have been setup by the > kernel in early boot before we got to efi_map_regions(), but we no > longer use the standard kernel page tables during EFI calls. > > Reported-by: Scott Ashcroft <scott.ashcroft@talk21.com> > Tested-by: Scott Ashcroft <scott.ashcroft@talk21.com> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Cc: Ben Hutchings <ben@decadent.org.uk> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Brian Gerst <brgerst@gmail.com> > Cc: Denys Vlasenko <dvlasenk@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> > Cc: Matthew Garrett <mjg59@srcf.ucam.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Raphael Hertzog <hertzog@debian.org> > Cc: Roger Shimizu <rogershimizu@gmail.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: linux-efi@vger.kernel.org > Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> > --- > arch/x86/mm/pageattr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c > index 14c38ae80409..fcf8e290740a 100644 > --- a/arch/x86/mm/pageattr.c > +++ b/arch/x86/mm/pageattr.c > @@ -1055,7 +1055,7 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, pgd_t *pgd, > /* > * Map everything starting from the Gb boundary, possibly with 1G pages > */ > - while (end - start >= PUD_SIZE) { > + while (cpu_has_gbpages && end - start >= PUD_SIZE) { > set_pud(pud, __pud(cpa->pfn << PAGE_SHIFT | _PAGE_PSE | > massage_pgprot(pud_pgprot))); > > --
Yap, looks ok to me as a minimal fix:
Acked-by: Borislav Petkov <bp@suse.de>
As a future cleanup, I'd carve out the sections of populate_pud() which map the stuff up to the Gb boundary and the trailing leftover into a helper, say, __populate_pud_chunk() or so which goes and populates with smaller sizes, i.e., 2M and 4K and the lower levels.
This'll make populate_pud() more readable too.
Thanks.
-- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.
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