Hi Tom, On Fri, Apr 29, 2022 at 08:08:28AM -0500, Tom Lendacky wrote: > On 4/29/22 04:06, Tao Liu wrote: > > On Thu, Jan 27, 2022 at 11:10:34AM +0100, Joerg Roedel wrote: > > > > > 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: > > Qemu was specifically patched to exit on reboot with SEV-ES guests. Qemu > performs a reboot by resetting the vCPU state, which can't be done with an > SEV-ES guest because the vCPU state is encrypted. >
Sorry for the late response, and thank you for the explanation! > > > > [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? > > The main goal of this patch set is to really to solve the ability to perform > a kexec. I would expect kdump to work since kdump shuts down all but the > executing vCPU and performs its operations before "rebooting" (which will > exit Qemu as I mentioned above). But kexec requires the need to restart the > APs from within the guest after they have been stopped. That requires > specific support and actions on the part of the guest kernel in how the APs > are stopped and restarted. Recently I got one sev-es flaged machine borrowed and retested the patch, which worked fine for kexec when sev-es enabled. With the patchset applied in 5.17.0-rc1, kexec'ed kernel can bring up all APs with no problem. However as for kdump, I find one issue. Although kdump kernel can work well on one cpu, but we can still enable multi-cpus by removing the "nr_cpus=1" kernel parameter in kdump sysconfig. I was expecting kdump kernel can bring up all APs as kexec did, however: [ 0.000000] Command line: elfcorehdr=0x5b000000 BOOT_IMAGE=(hd0,gpt2)/vmlinuz-5.17.0-rc1+ ro resume=/dev/mapper/rhel-swap biosdevname=0 net.ifnames=0 console=ttyS0 irqpoll reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 rootflags=nofail acpi_no_memhotplug transparent_hugepage=never nokaslr novmcoredd hest_disable disable_cpu_apicid=0 iTCO_wdt.pretimeout=0 ... [ 0.376663] smp: Bringing up secondary CPUs ... [ 0.377599] x86: Booting SMP configuration: [ 0.378342] .... node #0, CPUs: #1 [ 10.377698] smpboot: do_boot_cpu failed(-1) to wakeup CPU#1 [ 10.379882] #2 [ 20.379645] smpboot: do_boot_cpu failed(-1) to wakeup CPU#2 [ 20.380648] smp: Brought up 1 node, 1 CPU [ 20.381600] smpboot: Max logical packages: 4 [ 20.382597] smpboot: Total of 1 processors activated (4192.00 BogoMIPS) Turns out for kdump, the APs were not stopped properly, so I modified the following code: --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -26,6 +26,7 @@ #include <asm/cpu.h> #include <asm/nmi.h> #include <asm/smp.h> +#include <asm/sev.h> #include <linux/ctype.h> #include <linux/mc146818rtc.h> @@ -821,6 +822,7 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs) atomic_dec(&waiting_for_crash_ipi); /* Assume hlt works */ + sev_es_stop_this_cpu(); halt(); for (;;) cpu_relax(); [ 0.000000] Command line: elfcorehdr=0x5b000000 BOOT_IMAGE=(hd0,gpt2)/vmlinuz-5.17.0-rc1-hack+ ro resume=/dev/mapper/rhel-swap biosdevname=0 net.ifnames=0 console=ttyS0 irqpoll reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 rootflags=nofail acpi_no_memhotplug transparent_hugepage=never nokaslr novmcoredd hest_disable disable_cpu_apicid=0 iTCO_wdt.pretimeout=0 ... [ 0.402618] smp: Bringing up secondary CPUs ... [ 0.403308] x86: Booting SMP configuration: [ 0.404171] .... node #0, CPUs: #1 #2 #3 [ 0.407362] smp: Brought up 1 node, 4 CPUs [ 0.408907] smpboot: Max logical packages: 4 [ 0.409172] smpboot: Total of 4 processors activated (16768.01 BogoMIPS) Now all APs can work in kdump kernel. Thanks, Tao Liu > > Thanks, > Tom > > > > > Thanks, > > Tao Liu > > > _______________________________________________ > > > Virtualization mailing list > > > virtualizat...@lists.linux-foundation.org > > > https://lists.linuxfoundation.org/mailman/listinfo/virtualization > > > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec