linux-kernel - Re: Wake-up from suspend to RAM broken under `retbleed=stuff`

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Date:   Sun, 8 Jan 2023 22:27:45 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Joan Bruguera <joanbrugueram@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Wake-up from suspend to RAM broken under `retbleed=stuff`

On Sun, Jan 08, 2023 at 05:11:59PM +0000, Joan Bruguera wrote:
> Arch Linux kernel config (and I leave any new options at their defaults):
> https://aur.archlinux.org/cgit/aur.git/plain/config?h=linux-mainline&id=20ffc62e08f6b0d48a088bccb6e0c3606b88083a

That .config works here.

> I need to either disable the BPF LSM or apply this patch to boot it:
> https://lore.kernel.org/lkml/20230107051456.8800-1-joanbrugueram@gmail.com/
> I suspend with `systemctl suspend`. Waking up hangs with `retbleed=stuff`
> and works without it.

I booted another, more modern guest which has systemd to see whether a different
userspace could be the issue but it works too.
 
> For verification I booted Fedora-Cloud-Base-Rawhide-20230107.n.0.x86_64.qcow2
> (from https://dl.fedoraproject.org/pub/fedora/linux/development/rawhide/Cloud):
>     qemu-system-x86_64 -nodefaults -enable-kvm -smp 1 -m 1024 -vga std \
>         -hda Fedora-Cloud-Base-Rawhide-20230107.n.0.x86_64.qcow2 \
>         -serial stdio -monitor tcp:127.0.0.1:55555,server,nowait
> I appended `retbleed=stuff,force init=/bin/sh` to the kernel command line,
> suspended through sysfs and then wrote `system_wakeup` on the QEMU monitor.

I guess I'll try that next.

And maybe try that on an Intel machine - I'm using an AMD one but the ",force"
thing enables the same stuffing on AMD too even if it is not the fitting
mitigation for it.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette