[PATCH 0/3 v2] Add kdump support for the SEV enabled guest

[Lianbo Jiang]

Just like the physical machines support kdump, the virtual machines
also need kdump. When a virtual machine panic, we also need to dump
its memory for analysis.

For the SEV virtual machine, the memory is also encrypted. When SEV
is enabled, the first kernel is loaded into the encrypted area.
Unlike the SME, the first kernel is loaded into the decrypted area.

Because of this difference between SME and SEV, we need to properly
map the kexec memory area in order to correctly access it.

Test tools:
makedumpfile[v1.6.5]:
git://git.code.sf.net/p/makedumpfile/code
commit <d222b01e516b> ("Add support for AMD Secure Memory Encryption")
Note: This patch was merged into the devel branch.

crash-7.2.5: https://github.com/crash-utility/crash.git
commit <942d813cda35> ("Fix for the "kmem -i" option on Linux 5.0")

kexec-tools-2.0.19:
git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
commit <942d813cda35> ("Fix for the kmem '-i' option on Linux 5.0")
http://lists.infradead.org/pipermail/kexec/2019-March/022576.html
Note: The second kernel cann't boot without this patch.

kernel:
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
commit <f261c4e529da> ("Merge branch 'akpm' (patches from Andrew)")

Test steps:
[1] load the vmlinux and initrd for kdump
# kexec -p /boot/vmlinuz-5.0.0+ --initrd=/boot/initramfs-5.0.0+kdump.img --command-line="BOOT_IMAGE=(hd0,gpt2)/vmlinuz-5.0.0+ ro resume=UUID=126c5e95-fc8b-48d6-a23b-28409198a52e console=ttyS0,115200 earlyprintk=serial irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 rootflags=nofail acpi_no_memhotplug transparent_hugepage=never disable_cpu_apicid=0"

[2] trigger panic
# echo 1 > /proc/sys/kernel/sysrq
# echo c > /proc/sysrq-trigger

[3] check and parse the vmcore
# crash vmlinux /var/crash/127.0.0.1-2019-03-15-05\:03\:42/vmcore

Changes since v1:
1. Modify the patch subject prefixes.
2. Improve patch log: add parentheses at the end of the function names.
3. Fix the multiple confusing checks.
4. Add comment in the arch_kexec_post_alloc_pages().

Lianbo Jiang (3):
  x86/kexec: Do not map the kexec area as decrypted when SEV is active
  x86/kexec: Set the C-bit in the identity map page table when SEV is
    active
  kdump,proc/vmcore: Enable kdumping encrypted memory when SEV was
    active

 arch/x86/kernel/machine_kexec_64.c | 27 ++++++++++++++++++++++++++-
 fs/proc/vmcore.c                   |  6 +++---
 2 files changed, 29 insertions(+), 4 deletions(-)

-- 
2.17.1