在 2022/3/29 16:26, Ard Biesheuvel 写道:
On Sat, 26 Mar 2022 at 07:27, Wupeng Ma <mawupeng1@xxxxxxxxxx> wrote:
From: Ma Wupeng <mawupeng1@xxxxxxxxxx>
Commit b05b9f5f9dcf ("x86, mirror: x86 enabling - find mirrored memory ranges")
introduced mirrored memory support for x86. This support rely on UEFI to
report mirrored memory address ranges. See UEFI 2.5 spec pages 157-158:
http://www.uefi.org/sites/default/files/resources/UEFI%202_5.pdf
Arm64 can support this too. So mirrored memory support is added to support
arm64.
What is the point of this if the kernel itself is not loaded in
EFI_MORE_RELIABLE memory? On x86, this is handled by the decompressor,
but that does not exist on arm64.
Do you mean this is x86, commit c05cd79750fb
("x86/boot/KASLR: Prefer mirrored memory regions for the kernel physical address").
This scenario is not considered.
The problem here is that UEFI defines this as a memory *attribute*
rather than a memory *type*, which means you cannot allocate
EFI_MORE_RELIABLE memory easily: you have to iterate over the memory
map and look for regions with the desired attribute, and allocate
those pages explicitly. I'd prefer to implement this in the
bootloader, and only add minimal logic to the stub to respect the
placement of the kernel by the loader if the loader signals it to do
so (there are other reasons for this - I will cc you on a patch
shortly that implements this)
Thanks for your incoming patch.
This also means that the fake_mem stuff is not going to work: the
memory map observed by the stub comes straight from the firmware, and
if the stub needs to be involved in placing (or respecting the
placement by the loader of) the kernel image, it needs to observe
those EFI_MORE_RELIABLE regions too. If you don't have access to a
machine that actually exposes EFI_MORE_RELIABLE memory, I suggest you
prototype it in QEMU/edk2 instead.
You are right fake_mem stuff is not going to work. But, efi_fake_mem is
used for testing mirrored features and will not be used in production
environment. This test features can fake memory's attribute values.
The reason why efi_fake_mem support is put first is that memory's attribute
is reported by BIOS which is hard to simulate. With this support, any arm64
machines with efi support can easily test mirrored features.
In fact, we have been trying very hard not to touch the firmware
provided memory map at all on ARM, rather than use it as a scratchpad
for all kinds of annotations. This means, for instance, that kexec is
idempotent - the next kernel should not be affected by modifications
to the memory map applied by the previous kernel.
Yes, you're absolutely right. Efi_fake_mem is incompatible with kdump which
will use kexec. But we can remove specify cmdline(efi_fake_mem=xx) by
modofing /etc/sysconfig/kdump. Efi_fake_mem is only used for testing and
will not be used in production environment.
In summary, implementing kernelcore=mirror for arm64 is fine with me,
but there are some issues we need to address first.
Can you be clear what the issues are?
The main purpose of this patchset is to introduce mirrored support for
arm64 and we have already fixed the problems we had which is shown in
patch #5 to patch #7 and try to bring total isolation in patch #8 which
will disable mirror feature if kernelcore is not specified.
Thanks for reviewing.
Patch #1-#2 introduce efi_fake_mem support for arm64.
Patch #3-#4 introduce mirrored memory support form arm64.
Patch #5-#7 fix some bugs for arm64 if memory reliable is enabled.
Patch #8 disable mirror feature if kernelcore is not specified.
Patch #9 remove some redundant code in ia64 efi_init.
Ma Wupeng (9):
efi: Make efi_print_memmap() public
arm64: efi: Add fake memory support
efi: Make efi_find_mirror() public
arm64/mirror: arm64 enabling - find mirrored memory ranges
mm: Ratelimited mirrored memory related warning messages
mm: Demote warning message in vmemmap_verify() to debug level
mm: Calc the right pfn if page size is not 4K
efi: Disable mirror feature if kernelcore is not specified
ia64/efi: Code simplification in efi_init
.../admin-guide/kernel-parameters.txt | 4 +-
arch/arm64/kernel/setup.c | 3 ++
arch/ia64/kernel/efi.c | 37 +-----------------
arch/x86/include/asm/efi.h | 5 ---
arch/x86/platform/efi/efi.c | 39 -------------------
drivers/firmware/efi/Kconfig | 2 +-
drivers/firmware/efi/efi.c | 26 +++++++++++++
drivers/firmware/efi/memmap.c | 16 ++++++++
include/linux/efi.h | 4 ++
include/linux/mm.h | 2 +
mm/memblock.c | 4 +-
mm/page_alloc.c | 4 +-
mm/sparse-vmemmap.c | 2 +-
13 files changed, 60 insertions(+), 88 deletions(-)
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2.18.0.huawei.25
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