From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Young Subject: Re: [PATCH] x86/efi: Fix kexec kernel panic when efi=old_map is enabled Date: Tue, 16 May 2017 08:59:43 +0800 Message-ID: <20170516005943.GB3300@dhcp-128-65.nay.redhat.com> References: <1494271523-17331-1-git-send-email-sai.praneeth.prakhya@intel.com> <20170515132322.GB2935@codeblueprint.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170515132322.GB2935-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Matt Fleming Cc: Sai Praneeth Prakhya , linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Borislav Petkov , Ricardo Neri , Ard Biesheuvel , Ravi Shankar , joeyli List-Id: linux-efi@vger.kernel.org On 05/15/17 at 02:23pm, Matt Fleming wrote: > (Pulling in Dave, Mr. Kexec on EFI) > > On Mon, 08 May, at 12:25:23PM, Sai Praneeth Prakhya wrote: > > From: Sai Praneeth > > > > Booting kexec kernel with "efi=old_map" in kernel command line hits > > kernel panic as shown below. > > > > [ 0.001000] BUG: unable to handle kernel paging request at ffff88007fe78070 > > [ 0.001000] IP: virt_efi_set_variable.part.7+0x63/0x1b0 > > [ 0.001000] PGD 7ea28067 > > [ 0.001000] PUD 7ea2b067 > > [ 0.001000] PMD 7ea2d067 > > [ 0.001000] PTE 0 > > [ 0.001000] > > [ 0.001000] Oops: 0000 [#1] SMP > > [ 0.001000] Modules linked in: > > [ 0.001000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.11.0-rc2-yocto-standard+ #229 > > [ 0.001000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 > > [ 0.001000] task: ffffffff82022500 task.stack: ffffffff82000000 > > [ 0.001000] RIP: 0010:virt_efi_set_variable.part.7+0x63/0x1b0 > > [ 0.001000] RSP: 0000:ffffffff82003dc0 EFLAGS: 00010246 > > [ 0.001000] RAX: ffff88007fe78018 RBX: ffffffff82050300 RCX: 0000000000000007 > > [ 0.001000] RDX: ffffffff82003e50 RSI: ffffffff82050300 RDI: ffffffff82050300 > > [ 0.001000] RBP: ffffffff82003e08 R08: 0000000000000000 R09: 0000000000000000 > > [ 0.001000] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff82003e50 > > [ 0.001000] R13: 0000000000000007 R14: 0000000000000246 R15: 0000000000000000 > > [ 0.001000] FS: 0000000000000000(0000) GS:ffff88007fa00000(0000) knlGS:0000000000000000 > > [ 0.001000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 0.001000] CR2: ffff88007fe78070 CR3: 000000007da1d000 CR4: 00000000000006b0 > > [ 0.001000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > [ 0.001000] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > [ 0.001000] Call Trace: > > [ 0.001000] virt_efi_set_variable+0x5d/0x70 > > [ 0.001000] efi_delete_dummy_variable+0x7a/0x80 > > [ 0.001000] efi_enter_virtual_mode+0x3f6/0x4a7 > > [ 0.001000] start_kernel+0x375/0x400 > > [ 0.001000] x86_64_start_reservations+0x2a/0x2c > > [ 0.001000] x86_64_start_kernel+0x168/0x176 > > [ 0.001000] start_cpu+0x14/0x14 > > [ 0.001000] Code: 04 b0 84 ff 80 3d c5 56 b3 00 00 4c 8b 44 24 08 75 > > 6b 9c 41 5e 48 8b 05 9c 78 99 00 4d 89 c1 48 89 de 4d 89 f8 44 89 e9 4c > > 89 e2 <48> 8b 40 58 48 8b 78 58 e8 b0 2d 88 ff 48 c7 c6 b6 1d f4 81 4c > > [ 0.001000] RIP: virt_efi_set_variable.part.7+0x63/0x1b0 RSP: ffffffff82003dc0 > > [ 0.001000] CR2: ffff88007fe78070 > > [ 0.001000] ---[ end trace 0000000000000000 ]--- > > [ 0.001000] Kernel panic - not syncing: Attempted to kill the idle task! > > [ 0.001000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! > > > > This happens because efi=old_map doesn't use efi_pgd but rather it uses > > kernel's pgd. We don't hit the same panic in a regular kernel because > > it uses old_map_region() and not __map_region(). > > > > Signed-off-by: Sai Praneeth Prakhya > > Cc: Borislav Petkov > > Cc: Ricardo Neri > > Cc: Matt Fleming > > Cc: Ard Biesheuvel > > Cc: Ravi Shankar > > --- > > arch/x86/platform/efi/efi_64.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c > > index 4e043a8c8556..76e1cd6b74dd 100644 > > --- a/arch/x86/platform/efi/efi_64.c > > +++ b/arch/x86/platform/efi/efi_64.c > > @@ -320,6 +320,9 @@ static void __init __map_region(efi_memory_desc_t *md, u64 va) > > unsigned long pfn; > > pgd_t *pgd = efi_pgd; > > > > + if (efi_enabled(EFI_OLD_MEMMAP)) > > + pgd = swapper_pg_dir; > > + > > if (!(md->attribute & EFI_MEMORY_WB)) > > flags |= _PAGE_PCD; > > > > The thing is, efi=old_map was never intended to work with kexec. > > Part of the reason for introducing the new EFI runtime services > mapping scheme was so that we could kexec on EFI. See commit > d2f7cbe7b26a ("x86/efi: Runtime services virtual mapping"). > > The problem with using efi=old_map is that the virtual addresses are > assigned from the memory region used by other kernel mappings; > vmalloc() space. > > Potentially there could be collisions when booting kexec if something > else is mapped at the virtual address we allocated for runtime service > regions in the initial boot. > > So, while this patch may work for you and Joey, I don't think it's > reliable. > > Dave, did I miss anything? Matt, sorry for late reply, I did not notice this patch is kexec related and I missed it. Yes, you are right, efi=old_map is supposed not to work with kexec reboot because the runtime va is not persistent. The only way for old_map kexec boot is use below kexec-tools option to load kexec kernel: kexec --noefi and at the same time need pass acpi root pointer in kexec kernel cmdline: acpi_rsdp= Thanks Dave