• Lianbo Jiang's avatar
    x86/crash: Add e820 reserved ranges to kdump kernel's e820 table · 980621da
    Lianbo Jiang authored
    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: default avatarDave Young <dyoung@redhat.com>
    Signed-off-by: default avatarLianbo Jiang <lijiang@redhat.com>
    Signed-off-by: default avatarBorislav 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
    980621da