On Tue, 08 Oct, at 06:48:31PM, Borislav Petkov wrote: > From: Borislav Petkov <bp@xxxxxxx> > > We map the EFI regions needed for runtime services contiguously on > virtual addresses starting from -4G down for a total max space of 64G. > This way, we provide for stable runtime services addresses across > kernels so that a kexec'd kernel can still use them. > > This way, they're mapped in a separate pagetable so that we don't > pollute the kernel namespace (you can see how the whole ioremapping and > saving and restoring of PGDs is gone now). > > Also, add a chicken bit called "efi=old_map" which can be used as a > fallback to the old runtime services mapping method in case there's some > b0rkage with a particular EFI implementation (haha, it is hard to hold > up the sarcasm here...). > > Add UEFI RT VA space to Documentation/x86/x86_64/mm.txt, while at it. > > Signed-off-by: Borislav Petkov <bp@xxxxxxx> > --- > Documentation/x86/x86_64/mm.txt | 7 +++ > arch/x86/include/asm/efi.h | 47 ++++++++++++------- > arch/x86/include/asm/pgtable_types.h | 3 +- > arch/x86/platform/efi/efi.c | 91 ++++++++++++++++++++++++++---------- > arch/x86/platform/efi/efi_32.c | 8 +++- > arch/x86/platform/efi/efi_64.c | 83 ++++++++++++++++++++++++++++++++ > arch/x86/platform/efi/efi_stub_64.S | 54 +++++++++++++++++++++ > include/linux/efi.h | 1 + > 8 files changed, 251 insertions(+), 43 deletions(-) [...] > @@ -949,8 +978,17 @@ void __init efi_enter_virtual_mode(void) > count++; > } > > +#ifdef CONFIG_X86_64 > + efi_scratch.efi_pgt = (pgd_t *)(unsigned long)real_mode_header->trampoline_pgd; > + > + if (!test_bit(EFI_OLD_MEMMAP, &x86_efi_facility)) > + efi_scratch.use_pgd = true; > +#endif > + > BUG_ON(!efi.systab); Could you use the efi_enabled() function to test for EFI_OLD_MEMMAP instead of test_bit()? [...] > diff --git a/include/linux/efi.h b/include/linux/efi.h > index fa47d80ab4b5..beff433aa8c0 100644 > --- a/include/linux/efi.h > +++ b/include/linux/efi.h > @@ -632,6 +632,7 @@ extern int __init efi_setup_pcdp_console(char *); > #define EFI_RUNTIME_SERVICES 3 /* Can we use runtime services? */ > #define EFI_MEMMAP 4 /* Can we use EFI memory map? */ > #define EFI_64BIT 5 /* Is the firmware 64-bit? */ > +#define EFI_OLD_MEMMAP 6 /* Use old mapping method */ Hmm... I'm wondering whether this should actually be, #define EFI_ARCH_1 6 /* Architecture-specific option */ and in arch/x86/include/ we could then do, /* * Lots of info about why we need to switch to a new mapping scheme, but * also why the old scheme might be desirable.... */ #define EFI_OLD_MEMMAP EFI_ARCH_1 This way we won't exhaust the bitspace quite so soon (since ARM/ARM64 can reuse EFI_ARCH_1 if they need it), plus this memory mapping method is a very architecture-specific thing and so makes sense to hide it in the bowels of arch/x86. If it turns out that ARM/ARM64 need the exact same config option we can delete EFI_ARCH_1 and move EFI_OLD_MEMMAP to include/linux/efi.h just like in your original patch. What do you think? -- Matt Fleming, Intel Open Source Technology Center -- 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
