ACK: [G][PATCH 0/1] qemu (secure guest) crash due to gup_fast / dynamic page table folding issue (LP: 1896726)

[Thadeu Lima de Souza Cascardo]

On Thu, Sep 24, 2020 at 06:19:24PM +0200, frank.heimes at canonical.com wrote:
> BugLink: https://bugs.launchpad.net/bugs/1896726
> 
> Secure KVM guest (using secure execution on Ubuntu Server 20.04 for s390x)
> crashes happen from time to time during boot.
> Such crashed guests ("reason=crashed" in the libvirt log) end up in shutoff state
> instead of crashed state (<on_crash> preserve is set).
> The crash points to a kernel memory management problem, addressed by the following patch/fix.
> The modifications touch common memory management code,
> but it will have no effect to architectures other than s390x.
> This is ensured by the fact that only s390 provides / implements the new helper functions.
> And for s390x, this is actually a critical (and carefully tested) fix for a (previous) regression,
> so it can hardly get any more regressive.

Looking closely at the patch, it really looks like there are no changes for
other arches.

Acked-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>

> The patch landed upstream in linux-next, is in depth discussed
> at LKML https://lkml.kernel.org/r/20190418100218.0a4afd51@mschwideX1
> and here https://lore.kernel.org/linux-arch/patch.git-943f1e5dcff2.your-ad-here.call-01599856292-ext-8676@work.hours/
> and will soon land via the regular upstream stable release update for kernel 5.4 in focal, too.
> The process already started:
> https://lore.kernel.org/stable/patch-1.thread-41918b.git-41918be365c0.your-ad-here.call-01600439945-ext-8991@work.hours/
> 
> Hence this cherry-pick from the upstream patch should be added to groovy
> to avoid any potential regression in case the patch landed in focal via the upstream release update process,
> but is not in groovy and someones upgrades from focal to groovy.
> 
> Vasily Gorbik (1):
>   From: Vasily Gorbik <gor at linux.ibm.com>
> 
>  arch/s390/include/asm/pgtable.h | 42 +++++++++++++++++++++++----------
>  include/linux/pgtable.h         | 10 ++++++++
>  mm/gup.c                        | 18 +++++++-------
>  3 files changed, 49 insertions(+), 21 deletions(-)
> 
> -- 
> 2.25.1
> 
> 
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