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Date:   Mon, 22 Aug 2022 11:00:52 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc:     stable <stable@vger.kernel.org>,
        "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-x86_64@vger.kernel.org
Subject: Re: LTS kernel Linux 4.14.290 unable to boot with edk2-ovmf (x86_64
 UEFI runtime)
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On Mon, Aug 22, 2022 at 04:13:03PM +0800, Qu Wenruo wrote:
> 
> 
> On 2022/8/22 15:58, Greg KH wrote:
> > On Mon, Aug 22, 2022 at 03:49:51PM +0800, Qu Wenruo wrote:
> > > 
> > > 
> > > On 2022/8/22 15:33, Greg KH wrote:
> > > > On Mon, Aug 22, 2022 at 03:24:53PM +0800, Qu Wenruo wrote:
> > > > > 
> > > > > 
> > > > > On 2022/8/22 14:25, Greg KH wrote:
> > > > > > On Mon, Aug 22, 2022 at 09:15:59AM +0800, Qu Wenruo wrote:
> > > > > > > Hi,
> > > > > > > 
> > > > > > > When backporting some btrfs specific patches to all LTS kernels, I found
> > > > > > > v4.14.290 kernel unable to boot as a KVM guest with edk2-ovmf
> > > > > > > (edk2-ovmf: 202205, qemu 7.0.0, libvirt 1:8.6.0).
> > > > > > > 
> > > > > > > While all other LTS/stable branches (4.19.x, 5.4.x, 5.10.x, 5.15.x,
> > > > > > > 5.18.x, 5.19.x) can boot without a hipccup.
> > > > > > > 
> > > > > > > I tried the following configs, but none of them can even provide an
> > > > > > > early output:
> > > > > > > 
> > > > > > > - CONFIG_X86_VERBOSE_BOOTUP
> > > > > > > - CONFIG_EARLY_PRINTK
> > > > > > > - CONFIG_EARLY_PRINTK_EFI
> > > > > > > 
> > > > > > > Is this a known bug or something new?
> > > > > > 
> > > > > > Has this ever worked properly on this very old kernel tree?  If so, can
> > > > > > you use 'git bisect' to find the offending commit?
> > > > > 
> > > > > Unfortunately the initial v4.14 from upstream can not even be compiled.
> > > > 
> > > > Really?  Try using an older version of gcc and you should be fine.  It
> > > > did build properly back in 2017 when it was released :)
> > > 
> > > Yeah, I'm pretty sure my toolchain is too new for v4.14.0. But my distro
> > > only provides the latest and mostly upstream packages.
> > > 
> > > It may be a even worse disaster to find a way to rollback to older
> > > toolchains using my distro...
> > > 
> > > Also my hardware may not be well suited for older kernels either.
> > > (Zen 3 CPU used here)
> > > 
> > > In fact, I even find it hard just to locate a v4.14.x tag that can compile.
> > > After some bisection between v4.14.x tags, only v4.14.268 and newer tags
> > > can even be compiled using latest toolchain.
> > > (But still tons of warning, and tons of objdump warnings against
> > > insn_get_length()).
> > > 
> > > I'm not sure what's the normal practice for backports to such old branch.
> > > 
> > > Do you stable guys keep dedicated VMs loaded with older distro just for
> > > these old branches?
> > 
> > I don't, that's why those kernels can be built with newer versions of
> > gcc.
> > 
> > Your distro should have a version of gcc-10 or gcc-9 that can be
> > installed, right?
> 
> This may sounds like a meme, but I'm really using Archlinux for my VM
> and host, and it doesn't provide older GCC at all.

Archlinux does provide older gcc versions, that's what I use.

It still supports gcc11 in the main repo, and there is gcc10 in AUR as
well as gcc9.  Try those!

good luck!

greg k-h