[PATCHv3 00/14] x86/tdx: Add kexec support

[Baoquan He]

On 11/17/23 at 03:47pm, Kirill A. Shutemov wrote:
> On Thu, Nov 16, 2023 at 10:45:23PM +0800, Baoquan He wrote:
> > On 11/16/23 at 10:17pm, Baoquan He wrote:
> > > On 11/16/23 at 03:56pm, Kirill A. Shutemov wrote:
> > > > On Thu, Nov 16, 2023 at 08:10:47PM +0800, Baoquan He wrote:
> > > > > On 11/15/23 at 03:00pm, Kirill A. Shutemov wrote:
> > > > > > The patchset adds bits and pieces to get kexec (and crashkernel) work on
> > > > > > TDX guest.
> > > > > 
> > > > > I finally got a machine of intel-eaglestream-spr as host and built a
> > > > > tdx guest to give it a shot, the kexec reboot is working very well,
> > > > > while kdump kernel always failed to boot up. I only built kernel and
> > > > > installed it on tdx guest.
> > > > > ------------------------------------------
> > > > > [    1.422500] Run /init as init process
> > > > > [    1.423073] Failed to execute /init (error -2)
> > > > > [    1.423759] Run /sbin/init as init process
> > > > > [    1.424370] Run /etc/init as init process
> > > > > [    1.424969] Run /bin/init as init process
> > > > > [    1.425588] Run /bin/sh as init process
> > > > > [    1.426150] Kernel panic - not syncing: No working init found.  Try passing init= option to kernel. See Linux Documentation/admin-guide/init.rst for guidance.
> > > > > [    1.428122] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.7.0-rc1-00014-gbdba31ba3cec #3
> > > > > [    1.429232] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 2/2/2022
> > > > > [    1.430328] Call Trace:
> > > > > [    1.430717]  <TASK>
> > > > > [    1.431041]  dump_stack_lvl+0x33/0x50
> > > > > [    1.431581]  panic+0x324/0x340
> > > > > [    1.432037]  ? __pfx_kernel_init+0x10/0x10
> > > > > [    1.432629]  kernel_init+0x174/0x1c0
> > > > > [    1.433149]  ret_from_fork+0x2d/0x50
> > > > > [    1.433690]  ? __pfx_kernel_init+0x10/0x10
> > > > > [    1.434277]  ret_from_fork_asm+0x1b/0x30
> > > > > [    1.434850]  </TASK>
> > > > > [    1.435345] Kernel Offset: disabled
> > > > > [    1.439216] Rebooting in 10 seconds..
> > > > > qemu-kvm: cpus are not resettable, terminating
> > > > 
> > > > Could you shared your kernel config and details about your setup (qemu
> > > > command, kernel command line, ...)?
> > > 
> > > We followed tdx-tools README to setup the environment and built host and
> > > guest kernel, qemu command is as below. I copied the
> > > tdx-tools/build/rhel-9/intel-mvp-tdx-kernel/tdx-base.config to the
> > > latest upstream linxu kernel then execute 'make olddefconfig'. Because
> > > your patchset can't be applied to the stable kernel with the 731
> > > patches.
> > > 
> > > cd /home/root/tdx-tools
> > > ./start-qemu.sh -i /home/root/guest_tdx.qcow2 -b grub
> > 
> > This is the qemu command when execute above line of command, just for
> > your reference if you happen to not take this way.
> 
> Still failed to reproduce :/
> 
> Blind shot: could you check if the patch below makes any difference.

Still failed. And I found the normal reboot does't work either. I will
do more testing tomorrow, e.g use the tdx-tools's own rhel9 kernel
config and rebuild, and update host kernel too.

By the way, could you share your kernel config so that I can give it a
shot?

[  759.284783] [1320]: Remounting '/' read-only with options 'attr2,inode64,logbufs=8,logbsize=32k,noquota'.
[  759.291910] systemd-shutdown[1]: All filesystems unmounted.
[  759.292831] systemd-shutdown[1]: Deactivating swaps.
[  759.293579] systemd-shutdown[1]: All swaps deactivated.
[  759.294329] systemd-shutdown[1]: Detaching loop devices.
[  759.295419] systemd-shutdown[1]: All loop devices detached.
[  759.296221] systemd-shutdown[1]: Stopping MD devices.
[  759.296960] systemd-shutdown[1]: All MD devices stopped.
[  759.297726] systemd-shutdown[1]: Detaching DM devices.
[  759.298488] systemd-shutdown[1]: All DM devices detached.
[  759.299248] systemd-shutdown[1]: All filesystems, swaps, loop devices, MD devices and DM devices detached.
[  759.303358] systemd-shutdown[1]: Syncing filesystems and block devices.
[  759.304583] systemd-shutdown[1]: Rebooting.
[  759.306845] ACPI: PM: Preparing to enter system sleep state S5
[  759.307816] reboot: Restarting system
[  759.308355] reboot: machine restart
qemu-kvm: cpus are not resettable, terminating

> 
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 20e946c9a39d..8bb231e8ef9d 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -875,6 +875,8 @@ static void tdx_kexec_unshare_mem(bool crash)
>  	/* Stop new private<->shared conversions */
>  	conversion_allowed = false;
> 
> +	if (crash)
> +		return;
>  	/*
>  	 * Crash kernel reaches here with interrupts disabled: can't wait for
>  	 * conversions to finish.
> -- 
>   Kiryl Shutsemau / Kirill A. Shutemov
>