On 3/3/2025 2:49 PM, Sean Christopherson wrote: > On Mon, Mar 03, 2025, Ashish Kalra wrote: >> On 2/28/2025 4:32 PM, Sean Christopherson wrote: >>> On Fri, Feb 28, 2025, Ashish Kalra wrote: >>>> And the other consideration is that runtime setup of especially SEV-ES VMs will not >>>> work if/when first SEV-ES VM is launched, if SEV INIT has not been issued at >>>> KVM setup time. >>>> >>>> This is because qemu has a check for SEV INIT to have been done (via SEV platform >>>> status command) prior to launching SEV-ES VMs via KVM_SEV_INIT2 ioctl. >>>> >>>> So effectively, __sev_guest_init() does not get invoked in case of launching >>>> SEV_ES VMs, if sev_platform_init() has not been done to issue SEV INIT in >>>> sev_hardware_setup(). >>>> >>>> In other words the deferred initialization only works for SEV VMs and not SEV-ES VMs. >>> >>> In that case, I vote to kill off deferred initialization entirely, and commit to >>> enabling all of SEV+ when KVM loads (which we should have done from day one). >>> Assuming we can do that in a way that's compatible with the /dev/sev ioctls. >> >> Yes, that's what seems to be the right approach to enabling all SEV+ when KVM loads. >> >> For SEV firmware hotloading we will do implicit SEV Shutdown prior to DLFW_EX >> and SEV (re)INIT after that to ensure that SEV is in UNINIT state before >> DLFW_EX. >> >> We still probably want to keep the deferred initialization for SEV in >> __sev_guest_init() by calling sev_platform_init() to support the SEV INIT_EX >> case. > > Refresh me, how does INIT_EX fit into all of this? I.e. why does it need special > casing? For SEV INIT_EX, we need the filesystem to be up and running as the user-supplied SEV related persistent data is read from a regular file and provided to the INIT_EX command. Now, with the modified SEV/SNP init flow, when SEV/SNP initialization is performed during KVM module load, then as i believe the filesystem will be mounted before KVM module loads, so SEV INIT_EX can be supported without any issues. Therefore, we don't need deferred initialization support for SEV INIT_EX in case of KVM being loaded as a module. But if KVM module is built-in, then filesystem will not be mounted when SEV/SNP initialization is done during KVM initialization and in that case SEV INIT_EX cannot be supported. Therefore to support SEV INIT_EX when KVM module is built-in, the following will need to be done: - Boot kernel with psp_init_on_probe=false command line. - This ensures that during KVM initialization, only SNP INIT is done. - Later at runtime, when filesystem has already been mounted, SEV VM launch will trigger deferred SEV (INIT_EX) initialization (via the __sev_guest_init() -> sev_platform_init() code path). NOTE: psp_init_on_probe module parameter and deferred SEV initialization during SEV VM launch (__sev_guest_init()->sev_platform_init()) was added specifically to support SEV INIT_EX case. Thanks, Ashish
