Re: [ANNOUNCE] Xen 4.15 - call for notification/status of significant bugs

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.02.2021 13:12, Ian Jackson wrote:
> OPEN ISSUES
> -----------
> 
> A. HPET/PIT issue on newer Intel systems
> [...]
> 
> B. "scheduler broken" bugs.
> 
> Information from
>   Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>   Dario Faggioli <dfaggioli@xxxxxxxx>
> 
> Quoting Andrew Cooper
> | We've had 4 or 5 reports of Xen not working, and very little
> | investigation on whats going on.  Suspicion is that there might be
> | two bugs, one with smt=0 on recent AMD hardware, and one more
> | general "some workloads cause negative credit" and might or might
> | not be specific to credit2 (debugging feedback differs - also might
> | be 3 underlying issue).
> 
> I reviewed a thread about this and it is not clear to me where we are
> with this.

I'm not sure Marek's "Xen crash after S3 suspend - Xen 4.13 and newer"
falls in either of the two buckets.

> C. Fallout from MSR handling behavioral change.
> 
> Information from
>   Jan Beulich <jbeulich@xxxxxxxx>
> 
> I am lacking an extended desxcription of this.  What are the bug(s),
> and what is the situation ?
> 
> 
> D. Use-after-free in the IOMMU code
> 
> Information from
>   Julien Grall <julien@xxxxxxx>
> References
>  [PATCH for-4.15 0/4] xen/iommu: Collection of bug fixes for IOMMU teadorwn
>  <20201222154338.9459-1-julien@xxxxxxx>
> 
> Quoting the 0/:
> | This series is a collection of bug fixes for the IOMMU teardown code.
> | All of them are candidate for 4.15 as they can either leak memory or
> | lead to host crash/host corruption.
> 
> AFAIT these patches are not yet in-tree.

(since you're continuing with E. further down)

F. The almost-XSA "x86/PV: avoid speculation abuse through guest
accessors" - the first 4 patches are needed to address the actual
issue. The next 3 patches are needed to get the tree into
consistent state again, identifier-wise. The remaining patches
can probably wait.

> CLOSED ISSUES
> =============
> 
> E. zstd support
> 
> Information from
>   Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>   Jan Beulich <jbeulich@xxxxxxxx>
>   git
> 
> Needed to unbreak Fedora.  Needs support for both dom0 and domU.
> 
> AFAICT this seems to be in-tree as of 8169f82049ef
> "libxenguest: support zstd compressed kernels"

Indeed.

Jan