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    SubjectRe: [PATCH v4 1/5] efi: Export boot-services code and data as debugfs-blobs
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    Hi,

    On 26-04-18 18:51, Ard Biesheuvel wrote:
    > On 26 April 2018 at 14:06, Hans de Goede <hdegoede@redhat.com> wrote:
    >> Sometimes it is useful to be able to dump the efi boot-services code and
    >> data. This commit adds these as debugfs-blobs to /sys/kernel/debug/efi,
    >> but only if efi=debug is passed on the kernel-commandline as this requires
    >> not freeing those memory-regions, which costs 20+ MB of RAM.
    >>
    >> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    >> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
    >> ---
    >> Changes in v4:
    >> -Add new EFI_BOOT_SERVICES flag and use it to determine if the boot-services
    >> memory segments are available (and thus if it makes sense to register the
    >> debugfs bits for them)
    >>
    >> Changes in v2:
    >> -Do not call pr_err on debugfs call failures
    >> ---
    >> arch/x86/platform/efi/efi.c | 1 +
    >> arch/x86/platform/efi/quirks.c | 4 +++
    >> drivers/firmware/efi/efi.c | 53 ++++++++++++++++++++++++++++++++++
    >> include/linux/efi.h | 1 +
    >> 4 files changed, 59 insertions(+)
    >>
    >> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
    >> index 9061babfbc83..568b7ee3d323 100644
    >> --- a/arch/x86/platform/efi/efi.c
    >> +++ b/arch/x86/platform/efi/efi.c
    >> @@ -208,6 +208,7 @@ int __init efi_memblock_x86_reserve_range(void)
    >> efi.memmap.desc_version);
    >>
    >> memblock_reserve(pmap, efi.memmap.nr_map * efi.memmap.desc_size);
    >> + set_bit(EFI_BOOT_SERVICES, &efi.flags);
    >>
    >
    > I think it would be better if the flag conveys whether boot services
    > regions are being preserved, because they will always exist when
    > EFI_BOOT is set.
    > The name should then reflect that as well, e.g., EFI_PRESERVE_BS_REGIONS.

    Ok, I will rename the flag to EFI_PRESERVE_BS_REGIONS for v5
    (I'm going to wait a bit with sending out v5 to give others a change
    to comment on v4).

    >> return 0;
    >> }
    >> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
    >> index 36c1f8b9f7e0..16bdb9e3b343 100644
    >> --- a/arch/x86/platform/efi/quirks.c
    >> +++ b/arch/x86/platform/efi/quirks.c
    >> @@ -376,6 +376,10 @@ void __init efi_free_boot_services(void)
    >> int num_entries = 0;
    >> void *new, *new_md;
    >>
    >> + /* Keep all regions for /sys/kernel/debug/efi */
    >> + if (efi_enabled(EFI_DBG))
    >> + return;
    >> +
    >
    > Why is this only necessary when EFI_DBG is enabled? How are you
    > ensuring that the firmware is still in memory when the subsequent
    > patches start relying on that?

    The 2nd patch in this series makes init/main.c call
    efi_check_for_embedded_firmwares() before efi_free_boot_services(),
    efi_check_for_embedded_firmwares() then walks the dmi_system_id-s
    "registered" (its a static list) by drivers and if their is a dmi_match
    searches for the firmware described by the dmi_system_id.driver_data
    ptr. If a firmware gets found it gets memdup-ed, so that we do not
    have to keep all of the boot-services code around.

    Regards,

    Hans

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