It is convenient to remap the old memory encrypted to the second kernel by calling ioremap_encrypted().
When sme enabled on AMD server, we also need to support kdump. Because the memory is encrypted in the first kernel, we will remap the old memory encrypted to the second kernel(crash kernel), and sme is also enabled in the second kernel, otherwise the old memory encrypted can not be decrypted. Because simply changing the value of a C-bit on a page will not automatically encrypt the existing contents of a page, and any data in the page prior to the C-bit modification will become unintelligible. A page of memory that is marked encrypted will be automatically decrypted when read from DRAM and will be automatically encrypted when written to DRAM. For the kdump, it is necessary to distinguish whether the memory is encrypted. Furthermore, we should also know which part of the memory is encrypted or decrypted. We will appropriately remap the memory according to the specific situation in order to tell cpu how to deal with the data(encrypted or decrypted). For example, when sme enabled, if the old memory is encrypted, we will remap the old memory in encrypted way, which will automatically decrypt the old memory encrypted when we read those data from the remapping address. ---------------------------------------------- | first-kernel | second-kernel | kdump support | | (mem_encrypt=on|off) | (yes|no) | |--------------+---------------+---------------| | on | on | yes | | off | off | yes | | on | off | no | | off | on | no | |______________|_______________|_______________| Test tools: makedumpfile[v1.6.3]: https://github.com/LianboJ/makedumpfile commit e1de103eca8f (A draft for kdump vmcore about AMD SME) Author: Lianbo Jiang <liji...@redhat.com> Date: Mon May 14 17:02:40 2018 +0800 Note: This patch can only dump vmcore in the case of SME enabled. crash-7.2.1: https://github.com/crash-utility/crash.git commit 1e1bd9c4c1be (Fix for the "bpf" command display on Linux 4.17-rc1) Author: Dave Anderson <ander...@redhat.com> Date: Fri May 11 15:54:32 2018 -0400 Test environment: HP ProLiant DL385Gen10 AMD EPYC 7251 8-Core Processor 32768 MB memory 600 GB disk space Linux 4.17-rc4: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git commit 75bc37fefc44 ("Linux 4.17-rc4") Author: Linus Torvalds <torva...@linux-foundation.org> Date: Sun May 6 16:57:38 2018 -1000 Reference: AMD64 Architecture Programmer's Manual https://support.amd.com/TechDocs/24593.pdf Lianbo Jiang (2): add a function(ioremap_encrypted) for kdump when AMD sme enabled. support kdump when AMD secure memory encryption is active arch/x86/include/asm/dmi.h | 14 +++++++++++++- arch/x86/include/asm/io.h | 2 ++ arch/x86/kernel/acpi/boot.c | 8 ++++++++ arch/x86/kernel/crash_dump_64.c | 27 +++++++++++++++++++++++++++ arch/x86/mm/ioremap.c | 25 +++++++++++++++++-------- drivers/acpi/tables.c | 14 +++++++++++++- drivers/iommu/amd_iommu_init.c | 9 ++++++++- fs/proc/vmcore.c | 36 +++++++++++++++++++++++++++++++----- include/linux/crash_dump.h | 4 ++++ kernel/kexec_core.c | 12 ++++++++++++ 10 files changed, 135 insertions(+), 16 deletions(-) -- 2.9.5
