On Thu, Jan 27, 2022 at 11:10:34AM +0100, Joerg Roedel wrote: > From: Joerg Roedel <jroedel@xxxxxxx> > > Hi, > > here are changes to enable kexec/kdump in SEV-ES guests. The biggest > problem for supporting kexec/kdump under SEV-ES is to find a way to > hand the non-boot CPUs (APs) from one kernel to another. > > Without SEV-ES the first kernel parks the CPUs in a HLT loop until > they get reset by the kexec'ed kernel via an INIT-SIPI-SIPI sequence. > For virtual machines the CPU reset is emulated by the hypervisor, > which sets the vCPU registers back to reset state. > > This does not work under SEV-ES, because the hypervisor has no access > to the vCPU registers and can't make modifications to them. So an > SEV-ES guest needs to reset the vCPU itself and park it using the > AP-reset-hold protocol. Upon wakeup the guest needs to jump to > real-mode and to the reset-vector configured in the AP-Jump-Table. > > The code to do this is the main part of this patch-set. It works by > placing code on the AP Jump-Table page itself to park the vCPU and for > jumping to the reset vector upon wakeup. The code on the AP Jump Table > runs in 16-bit protected mode with segment base set to the beginning > of the page. The AP Jump-Table is usually not within the first 1MB of > memory, so the code can't run in real-mode. > > The AP Jump-Table is the best place to put the parking code, because > the memory is owned, but read-only by the firmware and writeable by > the OS. Only the first 4 bytes are used for the reset-vector, leaving > the rest of the page for code/data/stack to park a vCPU. The code > can't be in kernel memory because by the time the vCPU wakes up the > memory will be owned by the new kernel, which might have overwritten it > already. > > The other patches add initial GHCB Version 2 protocol support, because > kexec/kdump need the MSR-based (without a GHCB) AP-reset-hold VMGEXIT, > which is a GHCB protocol version 2 feature. > > The kexec'ed kernel is also entered via the decompressor and needs > MMIO support there, so this patch-set also adds MMIO #VC support to > the decompressor and support for handling CLFLUSH instructions. > > Finally there is also code to disable kexec/kdump support at runtime > when the environment does not support it (e.g. no GHCB protocol > version 2 support or AP Jump Table over 4GB). > > The diffstat looks big, but most of it is moving code for MMIO #VC > support around to make it available to the decompressor. > > The previous version of this patch-set can be found here: > > https://lore.kernel.org/lkml/20210913155603.28383-1-joro@xxxxxxxxxx/ > > Please review. > > Thanks, > > Joerg > > Changes v2->v3: > > - Rebased to v5.17-rc1 > - Applied most review comments by Boris > - Use the name 'AP jump table' consistently > - Make kexec-disabling for unsupported guests x86-specific > - Cleanup and consolidate patches to detect GHCB v2 protocol > support > > Joerg Roedel (10): > x86/kexec/64: Disable kexec when SEV-ES is active > x86/sev: Save and print negotiated GHCB protocol version > x86/sev: Set GHCB data structure version > x86/sev: Cache AP Jump Table Address > x86/sev: Setup code to park APs in the AP Jump Table > x86/sev: Park APs on AP Jump Table with GHCB protocol version 2 > x86/sev: Use AP Jump Table blob to stop CPU > x86/sev: Add MMIO handling support to boot/compressed/ code > x86/sev: Handle CLFLUSH MMIO events > x86/kexec/64: Support kexec under SEV-ES with AP Jump Table Blob > > arch/x86/boot/compressed/sev.c | 45 +- > arch/x86/include/asm/insn-eval.h | 1 + > arch/x86/include/asm/realmode.h | 5 + > arch/x86/include/asm/sev-ap-jumptable.h | 29 + > arch/x86/include/asm/sev.h | 11 +- > arch/x86/kernel/machine_kexec_64.c | 12 + > arch/x86/kernel/process.c | 8 + > arch/x86/kernel/sev-shared.c | 233 +++++- > arch/x86/kernel/sev.c | 404 +++++------ > arch/x86/lib/insn-eval-shared.c | 913 ++++++++++++++++++++++++ > arch/x86/lib/insn-eval.c | 909 +---------------------- > arch/x86/realmode/Makefile | 9 +- > arch/x86/realmode/rm/Makefile | 11 +- > arch/x86/realmode/rm/header.S | 3 + > arch/x86/realmode/rm/sev.S | 85 +++ > arch/x86/realmode/rmpiggy.S | 6 + > arch/x86/realmode/sev/Makefile | 33 + > arch/x86/realmode/sev/ap_jump_table.S | 131 ++++ > arch/x86/realmode/sev/ap_jump_table.lds | 24 + > 19 files changed, 1730 insertions(+), 1142 deletions(-) > create mode 100644 arch/x86/include/asm/sev-ap-jumptable.h > create mode 100644 arch/x86/lib/insn-eval-shared.c > create mode 100644 arch/x86/realmode/rm/sev.S > create mode 100644 arch/x86/realmode/sev/Makefile > create mode 100644 arch/x86/realmode/sev/ap_jump_table.S > create mode 100644 arch/x86/realmode/sev/ap_jump_table.lds > > > base-commit: e783362eb54cd99b2cac8b3a9aeac942e6f6ac07 > -- > 2.34.1 > Hi Joerg, I tried the patch set with 5.17.0-rc1 kernel, and I have a few questions: 1) Is it a bug or should qemu-kvm 6.2.0 be patched with specific patch? Because I found it will exit with 0 when I tried to reboot the VM with sev-es enabled. However with only sev enabled, the VM can do reboot with no problem: [root@dell-per7525-03 ~]# virsh start TW-SEV-ES --console .... Fedora Linux 35 (Server Edition) Kernel 5.17.0-rc1 on an x86_64 (ttyS0) .... [root@fedora ~]# reboot ..... [ 48.077682] reboot: Restarting system [ 48.078109] reboot: machine restart ^^^^^^^^^^^^^^^ guest vm reached restart [root@dell-per7525-03 ~]# echo $? 0 ^^^ qemu-kvm exit with 0, no reboot back to normal VM kernel [root@dell-per7525-03 ~]# 2) With sev-es enabled and the 2 patch sets applied: A) [PATCH v3 00/10] x86/sev: KEXEC/KDUMP support for SEV-ES guests, and B) [PATCH v6 0/7] KVM: SVM: Add initial GHCB protocol version 2 support. I can enable kdump and have vmcore generated: [root@fedora ~]# dmesg|grep -i sev [ 0.030600] SEV: Hypervisor GHCB protocol version support: min=1 max=2 [ 0.030602] SEV: Using GHCB protocol version 2 [ 0.296144] AMD Memory Encryption Features active: SEV SEV-ES [ 0.450991] SEV: AP jump table Blob successfully set up [root@fedora ~]# kdumpctl status kdump: Kdump is operational However without the 2 patch sets, I can also enable kdump and have vmcore generated: [root@fedora ~]# dmesg|grep -i sev [ 0.295754] AMD Memory Encryption Features active: SEV SEV-ES ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ patch set A & B not applied, so only have this string. [root@fedora ~]# echo c > /proc/sysrq-trigger ... [ 2.759403] kdump[549]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2022-04-18-05:58:50/ [ 2.804355] kdump[555]: saving vmcore-dmesg.txt complete [ 2.806915] kdump[557]: saving vmcore ^^^^^^^^^^^^^ vmcore can still be generated ... [ 7.068981] reboot: Restarting system [ 7.069340] reboot: machine restart [root@dell-per7525-03 ~]# echo $? 0 ^^^ same exit issue as question 1. I doesn't have a complete technical background of the patch set, but isn't it the issue which this patch set is trying to solve? Or I missed something? Thanks, Tao Liu > _______________________________________________ > Virtualization mailing list > Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx > https://lists.linuxfoundation.org/mailman/listinfo/virtualization
