On Tue, Jul 21, 2026 at 12:18:19PM +0100, Daniel P. Berrangé wrote:
> On Tue, Jul 21, 2026 at 11:09:11AM +0000, Zbigniew Jędrzejewski-Szmek wrote:
> > On Tue, Jul 21, 2026 at 12:49:59PM +0200, Arjun Shankar wrote:
> > > > > Wiki - https://fedoraproject.org/wiki/Changes/ShadowStack
> > > > > == Early Testing (Optional) ==
> > > > > A COPR repository with the updated glibc (Shadow Stack enabled) is
> > > > > available for Fedora 43, 44, and Rawhide for early testing:
> > > > > https://copr.fedorainfracloud.org/coprs/submachine/glibc-x86_64-SHSTK-Testing/
> > > >
> > > > This repo is not useful for testing of Rawhide now, because it's too 
> > > > old.
> > > > Packages have been rebuilt against newer glibc and installation fails 
> > > > with:
> > > >   - installed package sqlite-libs-3.53.3-1.fc45.x86_64 requires 
> > > > libm.so.6(GLIBC_2.44)(64bit),
> > > >     but none of the providers can be installed
> > > 
> > > I updated it, and it should now be up-to-date for Fedora 44 and 45
> > > now. I have dropped 43 and updated the change proposal to reflect
> > > this.
> > 
> > I saw that, thanks!
> > 
> > Second request: please enable the i686 build too. I have glibc.i686 
> > installed
> > for various reasons and the lack of the i686 build causes a problem with
> > the upgrade.
> > 
> > (Maybe this will help others trying to test this: qemu-10.x in F44 does
> > not have support for shadowstacks. After recompiling qemu from rawhide,
> > upgrading, and doing 'systemctl restart libvirtd', I get user_shstk
> > in /proc/cpuinfo on the guest.)
> 
> I'm surprised you see a difference in QEMU in this respect, as I'm
> not aware of changes between QEMU in 10.2.2 (F44) and 11.0.0 (F45)
> that would affect availability of shadow stacks in the guest VM.
> Do you have any ideas why it might be missing from F44.

I followed advice from Gemini. It said:
> Libvirt translates human-readable feature XML names into raw CPUID
> flags before sending them to QEMU. Because native KVM/QEMU
> hypervisor virtualization support for Intel/AMD CET (Control-flow
> Enforcement Technology) was fully integrated into QEMU 11.0, older
> versions of libvirt lack cet-ss and cet-ibt in their built-in CPU
> mapping definitions.
and gave a link to https://www.phoronix.com/news/QEMU-11.0-Released,
which says
> - QEMU 11.0 on KVM now supports Control-flow Enforcement Technology (CET) 
> virtualization.

>From my side, I noticed that my host CPU has user_shstk, but the
libvirt quest doesn't. The CPU was specified as 'host-passthrough'.

Zbyszek
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