linux-kernel - Re: [PATCHv3 00/14] x86/tdx: Add kexec support

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Message-ID: <20231117124748.umfuc3no2qvh4shj@box.shutemov.name>
Date:   Fri, 17 Nov 2023 15:47:48 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Kalra, Ashish" <ashish.kalra@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        "Huang, Kai" <kai.huang@...el.com>, kexec@...ts.infradead.org,
        linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 00/14] x86/tdx: Add kexec support

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.

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