On Sat, Sep 2, 2017 at 7:38 PM, Bhupesh Sharma <bhsharma@xxxxxxxxxx> wrote: > Hi Sai, > > On Tue, Aug 29, 2017 at 5:07 AM, Sai Praneeth Prakhya > <sai.praneeth.prakhya@xxxxxxxxx> wrote: >> From: Sai Praneeth <sai.praneeth.prakhya@xxxxxxxxx> >> >> Presently, in x86, to invoke any efi function like >> efi_set_virtual_address_map() or any efi_runtime_service() the code path >> typically involves read_cr3() (save previous pgd), write_cr3() >> (write efi_pgd) and calling efi function. Likewise after returning from >> efi function the code path typically involves read_cr3() (save efi_pgd), >> write_cr3() (write previous pgd). We do this couple of times in efi >> subsystem of Linux kernel, instead we can use helper function >> efi_switch_mm() to do this. This improves readability and maintainability. >> Also, instead of maintaining a separate struct "efi_scratch" to store/restore >> efi_pgd, we can use mm_struct to do this. >> >> I have tested this patch set against LUV (Linux UEFI Validation), so I >> think I didn't break any existing configurations. I have tested this >> patch set for >> 1. x86_64, >> 2. x86_32, >> 3. Mixed mode >> with efi=old_map and for kexec kernel. Please let me know if I have >> missed any other configurations. >> >> Changes in V2: >> 1. Resolve mm_dropping() issue by not mm_dropping()/mm_grabbing() any mm, >> as we are not losing/creating any references. >> >> Sai Praneeth (3): >> efi: Use efi_mm in x86 as well as ARM >> x86/efi: Replace efi_pgd with efi_mm.pgd >> x86/efi: Use efi_switch_mm() rather than manually twiddling with %cr3 >> >> arch/x86/include/asm/efi.h | 29 ++++++++++---------- >> arch/x86/platform/efi/efi_64.c | 52 ++++++++++++++++++++---------------- >> arch/x86/platform/efi/efi_thunk_64.S | 2 +- >> drivers/firmware/efi/arm-runtime.c | 9 ------- >> drivers/firmware/efi/efi.c | 9 +++++++ >> include/linux/efi.h | 2 ++ >> 6 files changed, 55 insertions(+), 48 deletions(-) >> >> -- >> 2.1.4 >> > > Thanks for this v2. > Introducing the 'efi_switch_mm() ' helper instead of manually > twiddling with %cr3 seems more cleaner. > > I have tested this patchset on a x86_64 machine with the following > configurations: > > 1. Primary kernel boot with efi=old_map > 2. Primary kernel boot with new efi map > > While it seems that efi=old_map passes, the new efi map boot fails for > me on both the two x86 machine (Dell 3050MT and a SGI - UV300 machine. > > It seems we are hitting a NULL pointer deference in > 'efi_call_phys_prolog' while accessing '&efi_mm'. > > Please see the log below for details: > > [ 0.020006] BUG: unable to handle kernel NULL pointer dereference > at (null) > [ 0.021000] IP: switch_mm_irqs_off+0x44/0x270 > [ 0.021000] PGD 0 > [ 0.021000] P4D 0 > [ 0.021000] > [ 0.021000] Oops: 0002 [#1] SMP > [ 0.021000] Modules linked in: > [ 0.021000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.12.0-rc7+ #8 > [ 0.021000] Hardware name: SGI UV300/UV300, BIOS SGI UV 300 series > BIOS 05/25/2016 > [ 0.021000] task: ffffffffb0e104c0 task.stack: ffffffffb0e00000 > [ 0.021000] RIP: 0010:switch_mm_irqs_off+0x44/0x270 > [ 0.021000] RSP: 0000:ffffffffb0e035d0 EFLAGS: 00010083 > [ 0.021000] RAX: 0000000000000000 RBX: ffffffffb0fbe620 RCX: ffffffffb0e61348 > [ 0.021000] RDX: ffffffffb0e104c0 RSI: ffffffffb0fbe620 RDI: ffffffffb0f14660 > [ 0.021000] RBP: ffffffffb0e035f0 R08: 65202c3120676f6c R09: 0000000000000189 > [ 0.021000] R10: 30313d6d6d5f6966 R11: 3432303331363936 R12: ffffffffb0f14660 > [ 0.021000] R13: 0000000000000000 R14: 0000000000000bb0 R15: 0000000000000450 > [ 0.021000] FS: 0000000000000000(0000) GS:ffff8bf2c3600000(0000) > knlGS:0000000000000000 > [ 0.021000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 0.021000] CR2: 0000000000000000 CR3: 0000005b43e09000 CR4: 00000000000406b0 > [ 0.021000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 0.021000] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 0.021000] Call Trace: > [ 0.021000] switch_mm+0x20/0x30 > [ 0.021000] efi_switch_mm+0x49/0x60 > [ 0.021000] efi_call_phys_prolog+0x56/0x1b3 > [ 0.021000] efi_enter_virtual_mode+0x3a9/0x520 > [ 0.021000] start_kernel+0x424/0x4c8 > [ 0.021000] ? set_init_arg+0x5a/0x5a > [ 0.021000] ? early_idt_handler_array+0x120/0x120 > [ 0.021000] x86_64_start_reservations+0x29/0x2b > [ 0.021000] x86_64_start_kernel+0x151/0x174 > [ 0.021000] secondary_startup_64+0x9f/0x9f > [ 0.021000] Code: 2d 82 51 d9 4f 65 c7 05 0f 65 da 4f 01 00 00 00 > 48 39 f7 0f 84 14 01 00 00 65 48 89 35 f6 64 da 4f 48 8b 86 e8 02 00 > 00 45 89 ed <f0> 4c 0f ab 28 bf 00 00 00 80 48 03 7e 50 48 8b 05 27 b0 > b9 00 > [ 0.021000] RIP: switch_mm_irqs_off+0x44/0x270 RSP: ffffffffb0e035d0 > [ 0.021000] CR2: 0000000000000000 > [ 0.021000] ---[ end trace fb94349305e1cb8b ]--- > [ 0.021000] Kernel panic - not syncing: Fatal exception > [ 0.021000] ---[ end Kernel panic - not syncing: Fatal exception > And I forgot to mention that I tried the patchset both with the efi/next and linus's trees and saw the same result. I would be happy to help in case you need further details of the test environment or need help in testing this crash further. Regards, Bhupesh -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
