(Sorry for the delay in replying to this) On Tue, 2013-01-08 at 09:02 -0600, Nathan Zimmer wrote: > Update efi_call_phys_prelog to install an identity mapping of all available > memory. This corrects a bug on very large systems with more then 512 GB in > which bios would not be able to access addresses above not in the mapping. > > The result is a crash that looks much like this. > > BUG: unable to handle kernel paging request at 000000effd870020 > IP: [<0000000078bce331>] 0x78bce330 > PGD 0 > Oops: 0000 [#1] SMP > Modules linked in: > CPU 0 > Pid: 0, comm: swapper/0 Tainted: G W 3.8.0-rc1-next-20121224-medusa_ntz+ #2 Intel Corp. Stoutland Platform > RIP: 0010:[<0000000078bce331>] [<0000000078bce331>] 0x78bce330 > RSP: 0000:ffffffff81601d28 EFLAGS: 00010006 > RAX: 0000000078b80e18 RBX: 0000000000000004 RCX: 0000000000000004 > RDX: 0000000078bcf958 RSI: 0000000000002400 RDI: 8000000000000000 > RBP: 0000000078bcf760 R08: 000000effd870000 R09: 0000000000000000 > R10: 0000000000000000 R11: 00000000000000c3 R12: 0000000000000030 > R13: 000000effd870000 R14: 0000000000000000 R15: ffff88effd870000 > FS: 0000000000000000(0000) GS:ffff88effe400000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000effd870020 CR3: 000000000160c000 CR4: 00000000000006b0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Process swapper/0 (pid: 0, threadinfo ffffffff81600000, task ffffffff81614400) > Stack: > 0000000078b80d18 0000000000000004 0000000078bced7b ffff880078b81fff > 0000000000000000 0000000000000082 0000000078bce3a8 0000000000002400 > 0000000060000202 0000000078b80da0 0000000078bce45d ffffffff8107cb5a > Call Trace: > [<ffffffff8107cb5a>] ? on_each_cpu+0x77/0x83 > [<ffffffff8102f4eb>] ? change_page_attr_set_clr+0x32f/0x3ed > [<ffffffff81035946>] ? efi_call4+0x46/0x80 > [<ffffffff816c5abb>] ? efi_enter_virtual_mode+0x1f5/0x305 > [<ffffffff816aeb24>] ? start_kernel+0x34a/0x3d2 > [<ffffffff816ae5ed>] ? repair_env_string+0x60/0x60 > [<ffffffff816ae2be>] ? x86_64_start_reservations+0xba/0xc1 > [<ffffffff816ae120>] ? early_idt_handlers+0x120/0x120 > [<ffffffff816ae419>] ? x86_64_start_kernel+0x154/0x163 > Code: Bad RIP value. > RIP [<0000000078bce331>] 0x78bce330 > RSP <ffffffff81601d28> > CR2: 000000effd870020 > ---[ end trace ead828934fef5eab ]--- > > v2: I noticed a typo on the one sent friday, also ccing the stable tree. > > > Cc: stable@xxxxxxxxxxxxxxx > Cc: Matt Fleming <matt.fleming@xxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Signed-off-by: Nathan Zimmer <nzimmer@xxxxxxx> > Signed-off-by: Robin Holt <holt@xxxxxxx> > --- > arch/x86/platform/efi/efi_64.c | 22 +++++++++++++++++----- > 1 files changed, 17 insertions(+), 5 deletions(-) The last time that the topic of introducing a proper identity pagetable came up was here, https://lkml.org/lkml/2012/10/5/253 mainly in the context of some firmware requiring physical mappings for I/O devices to persist even after we've called SetVirtualAddressMap(). It turns out that there's a bunch of places in the kernel that want this identity mapping - the one you've pointed out being yet another. > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c > index 95fd505..2b20038 100644 > --- a/arch/x86/platform/efi/efi_64.c > +++ b/arch/x86/platform/efi/efi_64.c > @@ -38,7 +38,7 @@ > #include <asm/cacheflush.h> > #include <asm/fixmap.h> > > -static pgd_t save_pgd __initdata; > +static pgd_t *save_pgd __initdata; > static unsigned long efi_flags __initdata; > > static void __init early_code_mapping_set_exec(int executable) > @@ -61,12 +61,20 @@ static void __init early_code_mapping_set_exec(int executable) > void __init efi_call_phys_prelog(void) > { > unsigned long vaddress; > + int pgd; > + int n_pgds; > > early_code_mapping_set_exec(1); > local_irq_save(efi_flags); > - vaddress = (unsigned long)__va(0x0UL); > - save_pgd = *pgd_offset_k(0x0UL); > - set_pgd(pgd_offset_k(0x0UL), *pgd_offset_k(vaddress)); > + > + n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE); > + save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_KERNEL); There's potential for this to be called under a spinlock, e.g. from phys_efi_get_time(). Maybe this should be GFP_ATOMIC? > + for (pgd = 0; pgd < n_pgds; pgd++) { > + save_pgd[pgd] = *pgd_offset_k(pgd * PGDIR_SIZE); > + vaddress = (unsigned long)__va(pgd * PGDIR_SIZE); > + set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), *pgd_offset_k(vaddress)); > + } > __flush_tlb_all(); > } > > @@ -75,7 +83,11 @@ void __init efi_call_phys_epilog(void) > /* > * After the lock is released, the original page table is restored. > */ > - set_pgd(pgd_offset_k(0x0UL), save_pgd); > + int pgd; > + int n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT) , PGDIR_SIZE); > + for (pgd = 0; pgd < n_pgds; pgd++) > + set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), save_pgd[pgd]); > + kfree(save_pgd); > __flush_tlb_all(); > local_irq_restore(efi_flags); > early_code_mapping_set_exec(0); I initially wrote a patch that was a little like this but Peter suggested making use of trampoline_pgd on x86-64 and switching between pagetables with CR3. While that's certainly the approach we should take going forward, this patch does look pretty trivial (making it suitable for stable) and it fixes a crash. So unless anyone's got an objection I'm happy to queue this up. -- 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
