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keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <65789d8b-d18f-4f1c-8ffc-e1247daa4031@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-purgate-ID: tlsNG-16d1c6/1787140611-F440377B-DA05CDEC/0/0 X-purgate-type: clean X-purgate-size: 2912 On 19.08.2026 13:13, Andrew Cooper wrote: > On 18/08/2026 3:31 pm, Jan Beulich wrote: >> On 18.08.2026 15:07, Andrew Cooper wrote: >>> Panicing in the case of a timeout turns out to be about the worst possible >>> action Xen can take. It leaves all other APs waiting on the condition >>> variable, some in NMI context. As a result, they fail to be shot down and >>> dump state for kexec crash analysis. >> At the same time there likely isn't much to be learned from a kexec dump, as >> the source of the issue is in the CPU, not in Xen. > > The single most valuable print message I've ever added to Xen is the one > which reports which CPUs didn't respond to NMIs.  Up until now, it has > always highlighted hardware issues. > > Despite my wish to remove this panic specifically, there is still > information to be gained from kexec in a similar scenario. That is you think of a system without console, where those log messages would only be possible to fish out of the dump. Fair enough. >> Further, this code runs with the watchdog disabled. If there's truly no >> progress anymore, how would one know from the outside whether the system is >> dead altogether vs the control CPU still kicking around? > > The scenario you describe can only occur if the BSP accepts the > microcode successfully, and one of the APs locks up properly. > > If the BSP locks up, we never get as far as deciding to panic(), and the > system hangs already. > > If we have a bad microcode, it is far more likely for the BSP to hang > than for the BSP to work one of the APs hang. Hmm, probably. (I'm always having in mind the one old system I have where only the primary cores on each socket get ucode updated by firmware, with secondary cores needing us to deal with them.) Still somewhat hesitantly: Acked-by: Jan Beulich >>> Microcode Loading on Granite Rapids takes about 4.5s of wallclock time, far in >>> excess of the of the arbitrary 1s Xen allows. This time is spent in the WRMSR >>> to load the blob, and there's nothing the system can do but to sit and wait. >>> Despite the delay, the system as a whole does survive. >> For this I wonder whether the log message issues after 1 sec is adequate. If >> we know things can take this long, wouldn't we better issue the log message >> no earlier than, say, 5s * nr_sockets? > > I have some work there not submitted yet, which would periodically print > a message.  That at least gives you slight signs of life. > > But nothing involving nr_sockets.  It's far more often wrong than it is > right, and that's not how our algorithm scales. > > GNR has gone from milliseconds to 4.5s.  Putting the limit at 5s is just > going to need another change in a year or two. That's one possibility, yes. The other is that they realize that they have to bring processing time back down. Jan