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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-06-19 at 15:17 +0200, Henrik B=C3=B6ving wrote: > [1.] One line summary of the problem > Probabilistic segfault on AMD hardware with INVLPGB >=20 > [2.] Full description of the problem/report: >=20 > Since upgrading from kernel 6.14 to 7.1, we've been observing > probabilistic segfaults on our build machines. We were able to > reproduce > these segfaults on two copies of the same hardware, equipped with an > AMD EPYC 9455 48-Core Processor. Subsequently, we managed to bisect > the > segfault down to the introduction of INVLPGB-based page invalidation > by > enabling/disabling BROADCAST_TLB_FLUSH on kernel 6.15. The segfaults > also do not reproduce on hardware that does not have the INVLPGB > instruction. >=20 We have also seen increased segfault rates when we first deployed Turin CPUs. This turned out to be AMD erratum AMD-SB-3029. Upgrading the firmware on the host solved those segfaults for us. Doing a bulk data analysis across the Meta fleet shows that Turin segfault rates are in the same range as those of other CPU microarchitectures, of several vendors. https://www.amd.com/en/resources/product-security/bulletin/amd-sb-3029.html Now, it is possible that INVLPGB has increased the likelihood of hitting some race condition, and it also possible that the kernel has a TLB flushing bug somewhere, but it may make sense to start with a firmware upgrade. --=20 All Rights Reversed.