From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH] x86/efi: Don't unmap EFI boot services code/data regions for EFI_OLD_MEMMAP and EFI_MIXED_MODE Date: Sat, 22 Dec 2018 11:54:10 +0100 Message-ID: <20181222105410.GA130780@gmail.com> References: <20181222022234.7573-1-sai.praneeth.prakhya@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181222022234.7573-1-sai.praneeth.prakhya@intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Sai Praneeth Prakhya Cc: linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, Borislav Petkov , Andy Lutomirski , Dave Hansen , Bhupesh Sharma , Peter Zijlstra , Thomas Gleixner , Ard Biesheuvel List-Id: linux-efi@vger.kernel.org * Sai Praneeth Prakhya wrote: > Commit d5052a7130a6 ("x86/efi: Unmap EFI boot services code/data regions > from efi_pgd") forgets to take two EFI modes into consideration namely > EFI_OLD_MEMMAP and EFI_MIXED_MODE. So the commit sha1 ended up being this one in tip:efi/core: 08cfb38f3ef4: x86/efi: Unmap EFI boot services code/data regions from efi_pgd > EFI_OLD_MEMMAP is a legacy way of mapping EFI regions into swapper_pg_dir > using ioremap() and init_memory_mapping(). This feature can be enabled by > passing "efi=old_map" as kernel command line argument. But, > efi_unmap_pages() unmaps EFI boot services code/data regions *only* from > efi_pgd and hence cannot be used for unmapping EFI boot services code/data > regions from swapper_pg_dir. > > Introduce a temporary fix to not unmap EFI boot services code/data regions > when EFI_OLD_MEMMAP is enabled while working on a real fix. > > EFI_MIXED_MODE is another feature where a 64-bit kernel runs on a > 64-bit platform crippled by a 32-bit firmware. To support EFI_MIXED_MODE, > all RAM (i.e. namely EFI regions like EFI_CONVENTIONAL_MEMORY, > EFI_LOADER_, EFI_BOOT_SERVICES_ and > EFI_RUNTIME_CODE/DATA regions) is mapped into efi_pgd all the time to > facilitate EFI runtime calls access it's arguments in 1:1 mode. Hence, > don't unmap EFI boot services code/data regions when booted in mixed mode. > > Signed-off-by: Sai Praneeth Prakhya > Cc: Borislav Petkov > Cc: Ingo Molnar > Cc: Andy Lutomirski > Cc: Dave Hansen > Cc: Bhupesh Sharma > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Cc: Ard Biesheuvel > --- > arch/x86/platform/efi/quirks.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c > index 09e811b9da26..9c34230aaeae 100644 > --- a/arch/x86/platform/efi/quirks.c > +++ b/arch/x86/platform/efi/quirks.c > @@ -380,6 +380,22 @@ static void __init efi_unmap_pages(efi_memory_desc_t *md) > u64 pa = md->phys_addr; > u64 va = md->virt_addr; > > + /* > + * To Do: Remove this check after adding functionality to unmap EFI boot > + * services code/data regions from direct mapping area because > + * "efi=old_map" maps EFI regions in swapper_pg_dir. > + */ > + if (efi_enabled(EFI_OLD_MEMMAP)) > + return; > + > + /* > + * EFI mixed mode has all RAM mapped to access arguments while making > + * EFI runtime calls, hence don't unmap EFI boot services code/data > + * regions. > + */ > + if (!efi_is_native() && IS_ENABLED(CONFIG_EFI_MIXED)) > + return; I suppose old_mmap and mixed mode stopped working altogether after the unmapping changes? What are the symptoms, instant reboots, crasher, or some more benign behavior like non-working runtime EFI functionality? If Ard acks this I'll apply it immediately, as these bugs look like show-stoppers for merging the EFI tree into v4.21. Thanks, Ingo