On Sat, Dec 17, 2022 at 06:42:05PM +0100, Neowutran wrote: > xen/arch/x86/time.c: Bug fix - Integer overflow when cpu frequency > u32 max > value. > > What is was trying to do: I was trying to install QubesOS on my new computer > (AMD zen4 processor). Guest VM were unusably slow / unusable. > > What is the issue: The cpu frequency reported is wrong for linux guest in HVM > and PVH mode, and it cause issue with the TSC clocksource (for example). > > Why this patch solved my issue: > The root cause it that "d->arch.tsc_khz" is a unsigned integer storing > the cpu frequency in khz. It get multiplied by 1000, so if the cpu frequency > is over ~4,294 Mhz (u32 max value), then it overflow. > I am solving the issue by adding an explicit cast to u64 to avoid the > overflow.
https://wiki.xenproject.org/wiki/Submitting_Xen_Project_Patches You're not matching the instructions. You need to add a "Signed-off-by" to indicate *you* wrote this, own the Copyright and are providing this under the license of the existing files. Your title line is on the long side. The discussion is useful for the message on the xen-devel mailing list, but isn't important for source code history. You should put "---" after the commit message and discussion below. I would suggest as a commit message: --------8<-----------------------------------------------------8<-------- xen/x86: prevent overflow with high frequency TSCs Promote tsc_khz to a 64-bit type before multiplying by 1000. Otherwise just above 4.294GHz the value will overflow. Processors with clocks this high are now in production and require this to work correctly. --------8<-----------------------------------------------------8<-------- Feel free to disagree, though any maintainer is going to want adjustments to your original commit message. Note to Xen and Linux distribution maintainers: I suggest this needs a point release of Xen. A large processor manufacturer has recently released such a processor. A great number of people are going to be rather unhappy in short order without this fix. -- (\___(\___(\______ --=> 8-) EHM <=-- ______/)___/)___/) \BS ( | ehem+sig...@m5p.com PGP 87145445 | ) / \_CS\ | _____ -O #include <stddisclaimer.h> O- _____ | / _/ 8A19\___\_|_/58D2 7E3D DDF4 7BA6 <-PGP-> 41D1 B375 37D0 8714\_|_/___/5445
