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980621daf3
At present, when using the kexec_file_load() syscall to load the kernel image and initramfs, for example: kexec -s -p xxx the kernel does not pass the e820 reserved ranges to the second kernel, which might cause two problems: 1. MMCONFIG: A device in PCI segment 1 cannot be discovered by the kernel PCI probing without all the e820 I/O reservations being present in the e820 table. Which is the case currently, because the kdump kernel does not have those reservations because the kexec command does not pass the I/O reservation via the "memmap=xxx" command line option. Further details courtesy of Bjorn Helgaas¹: I think you should regard correct MCFG/ECAM usage in the kdump kernel as a requirement. MMCONFIG (aka ECAM) space is described in the ACPI MCFG table. If you don't have ECAM: (a) PCI devices won't work at all on non-x86 systems that use only ECAM for config access, (b) you won't be able to access devices on non-0 segments (granted, there aren't very many of these yet, but there will be more in the future), and (c) you won't be able to access extended config space (addresses 0x100-0xfff), which means none of the Extended Capabilities will be available (AER, ACS, ATS, etc). 2. The second issue is that the SME kdump kernel doesn't work without the e820 reserved ranges. When SME is active in the kdump kernel, those reserved regions are still decrypted, but because those reserved ranges are not present at all in kdump kernel's e820 table, they are accessed as encrypted. Which is obviously wrong. [1]: https://lkml.kernel.org/r/CABhMZUUscS3jUZUSM5Y6EYJK6weo7Mjj5-EAKGvbw0qEe%2B38zw@mail.gmail.com [ bp: Heavily massage commit message. ] Suggested-by: Dave Young <dyoung@redhat.com> Signed-off-by: Lianbo Jiang <lijiang@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Baoquan He <bhe@redhat.com> Cc: Bjorn Helgaas <bjorn.helgaas@gmail.com> Cc: dave.hansen@linux.intel.com Cc: Dave Young <dyoung@redhat.com> Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: kexec@lists.infradead.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: x86-ml <x86@kernel.org> Cc: Yi Wang <wang.yi59@zte.com.cn> Link: https://lkml.kernel.org/r/20190423013007.17838-4-lijiang@redhat.com |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.