On 2014/4/14 19:14, Marc Zyngier wrote: > On 14/04/14 11:43, Will Deacon wrote: >> (catching up on old email) >> >> On Tue, Mar 18, 2014 at 07:35:59AM +0000, Jianguo Wu wrote: >>> Cloud you please take a look at this? >> >> [...] >> >>> On 2014/2/17 15:05, Jianguo Wu wrote: >>>> When enable LPAE and big-endian in a hisilicon board, while specify >>>> mem=384M mem=512M@7680M, will get bad page state: >>>> >>>> Freeing unused kernel memory: 180K (c0466000 - c0493000) >>>> BUG: Bad page state in process init pfn:fa442 >>>> page:c7749840 count:0 mapcount:-1 mapping: (null) index:0x0 >>>> page flags: 0x40000400(reserved) >>>> Modules linked in: >>>> CPU: 0 PID: 1 Comm: init Not tainted 3.10.27+ #66 >>>> [<c000f5f0>] (unwind_backtrace+0x0/0x11c) from [<c000cbc4>] (show_stack+0x10/0x14) >>>> [<c000cbc4>] (show_stack+0x10/0x14) from [<c009e448>] (bad_page+0xd4/0x104) >>>> [<c009e448>] (bad_page+0xd4/0x104) from [<c009e520>] (free_pages_prepare+0xa8/0x14c) >>>> [<c009e520>] (free_pages_prepare+0xa8/0x14c) from [<c009f8ec>] (free_hot_cold_page+0x18/0xf0) >>>> [<c009f8ec>] (free_hot_cold_page+0x18/0xf0) from [<c00b5444>] (handle_pte_fault+0xcf4/0xdc8) >>>> [<c00b5444>] (handle_pte_fault+0xcf4/0xdc8) from [<c00b6458>] (handle_mm_fault+0xf4/0x120) >>>> [<c00b6458>] (handle_mm_fault+0xf4/0x120) from [<c0013754>] (do_page_fault+0xfc/0x354) >>>> [<c0013754>] (do_page_fault+0xfc/0x354) from [<c0008400>] (do_DataAbort+0x2c/0x90) >>>> [<c0008400>] (do_DataAbort+0x2c/0x90) from [<c0008fb4>] (__dabt_usr+0x34/0x40) >> >> [...] >> >>>> The bug is happened in cpu_v7_set_pte_ext(ptep, pte): >>>> when pte is 64-bit, for little-endian, will store low 32-bit in r2, >>>> high 32-bit in r3; for big-endian, will store low 32-bit in r3, >>>> high 32-bit in r2, this will cause wrong pfn stored in pte, >>>> so we should exchange r2 and r3 for big-endian. >> Hi Marc, How about this: The bug is happened in cpu_v7_set_pte_ext(ptep, pte): - It tests the L_PTE_NONE in one word on the other, and possibly clear L_PTE_VALID tst r3, #1 << (57 - 32) @ L_PTE_NONE bicne r2, #L_PTE_VALID - Same for L_PTE_DIRTY, respectively setting L_PTE_RDONLY As for LPAE, the pte is 64-bits, and the value of r2/r3 is depending on the endianness, for little-endian, will store low 32-bit in r2, high 32-bit in r3, for big-endian, will store low 32-bit in r3, high 32-bit in r2, this will cause wrong bit is cleared or set, and get wrong pfn. So we should exchange r2 and r3 for big-endian. Thanks, Jianguo Wu. >> I believe that Marc (added to CC) has been running LPAE-enabled, big-endian >> KVM guests without any issues, so it seems unlikely that we're storing the >> PTEs backwards. Can you check the configuration of SCTLR.EE? > > So, for the record: > > root@when-the-lie-s-so-big:~# cat /proc/cpuinfo > processor : 0 > model name : ARMv7 Processor rev 4 (v7b) > Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm > CPU implementer : 0x41 > CPU architecture: 7 > CPU variant : 0x0 > CPU part : 0xc07 > CPU revision : 4 > > processor : 1 > model name : ARMv7 Processor rev 4 (v7b) > Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm > CPU implementer : 0x41 > CPU architecture: 7 > CPU variant : 0x0 > CPU part : 0xc07 > CPU revision : 4 > > Hardware : Dummy Virtual Machine > Revision : 0000 > Serial : 0000000000000000 > root@when-the-lie-s-so-big:~# uname -a > Linux when-the-lie-s-so-big 3.14.0+ #2465 SMP PREEMPT Tue Apr 8 13:05:11 BST 2014 armv7b GNU/Linux > > Now, looking at the patch, I think it makes some sense: > - Depending on the endianness, we have to test the L_PTE_NONE in one > word on the other, and possibly clear L_PTE_VALID > - Same for L_PTE_DIRTY, respectively setting L_PTE_RDONLY > > The commit message looks wrong though, as it mention the PTE storage in > memory (which looks completely fine to me, and explain why I was able to > boot a guest). As none of my guest RAM is above 4GB IPA, I didn't see > the corruption of bit 32 in the PTE (which should have been bit 0, > corresponding to L_PTE_VALID). > > So, provided that the commit message is rewritten to match the what it does, > I'm fine with that patch. > > Thanks, > > M. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>