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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 Wed, 2026-05-13 at 09:31 -0700, Dave Hansen wrote: > On 5/13/26 09:12, Rik van Riel wrote: > > This reduces the NMI/RC2 race window by 90% -- from hundreds of C > > instructions deep in the handler down to ~30 asm instructions in > > error_entry. >=20 > I'm all for using the FRED data. That's a no-brainer. >=20 > But I'm not sure the assembly and plumbing is worth it just to > _reduce_ > but not eliminate a race for non-FRED systems. >=20 > What's the actual end-user-visible fallout from the race? Don't we > just > see the KASAN fault, skip it, IRET from the #PF and repeat the #PF? That's a good question. I have only "seen" this in syzkaller, so I don't know what the symptoms would look like if a regular system hit this race window. I would not be surprised if we occasionally hit this in production, but given that I don't know what the symptoms would look like, I have no idea how often. --=20 All Rights Reversed.