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Can init and shutdown race? Isn't that part of module load / >>> unload, I'm not sure how they can race... >> >> That's only true after >> https://lore.kernel.org/all/20260504165147.1615643-5-tycho@kernel.org/ >> right? Before that, if the first init failed, you could trigger a >> re-init via ioctl(), and presumably trigger the race sashiko is >> complaining about by spamming ioctl() + sysfs writes on separate >> threads. Yes, this is the race I had in mind and probably what sashiko complained about in it's review too. I missed this patch from earlier. This should avoid any racing. >> >>>> t1 | t2 >>>> ---------------------------------- | ---------------------------------- >>>> sev_firmware_shutdown() | sev_platform_init() >>>> unregister_verify_mitigation() | register_verify_mitigation() >>>> sysfs_remove_group() | sysfs_create_group() >>>> >>>> Both sides touch sev->verify_mit without serialization. The same race also >>>> exists for init vs init which is no longer covered by sev_cmd_mutex once >>>> register moves outside it. >>> >>> I don't think you can have init vs init race, can you? This just all seems >>> odd to me. Have you created all these race scenarios to test this out? >>> >>> Would putting the regsiter/unregister under the sev_cmd_mutex and then >>> taking the sev_cmd_mutex upon entry to _show()/_store() fix all this? >>> After obtaining the mutex in _show()/_store(), you check for >>> sev->verify_mit and return an error if NULL. Then you can use the >>> __sev_do_cmd_locked() to issue any commands. >> >> As long as sysfs_remove_group() happens before >> __sev_firmware_shutdown() it seems like it should be fine since sysfs >> will do its own synchronization. IIUC we might not need this locking >> at all assuming the above is applied? > > That's what I'm thinking. I'll let Pratik confirm. > Yes, sysfs should do its own synchronization and I'm assuming this means that we don't need any locks anymore and I can get rid of the sev_mit_sysfs_mutex and move unregister outside the sev_cmd_mutex. I tested this with putting a msleep() in the _show()/_store() and in parallel rmmod calling shutdown. This seems to work without issues whereas with the former approach I could deadlock waiting on sev_cmd_mutex. > >>> Also, on the register function, all you need is the check for >>> !(sev->snp_feat_info_0.ecx & SNP_VERIFY_MITIGATION_SUPPORTED) since if >>> !sev->snp_plat_status.feature_info is true, so is this this check. And, as >>> the spec says, the required firmware state is based on the mitigation >>> requirements, so I don't think you should be checking for snp_initialized. Ack, will just keep the SNP_VERIFY_MITIGATION_SUPPORTED check in the next iteration. Thanks Tom and Tycho! --Pratik > Thanks, > Tom > >> >> Tycho >