On 23/11/2020 09.07, Christian Borntraeger wrote: > > > On 23.11.20 09:05, Thomas Huth wrote: >> On 23/11/2020 08.39, Christian Borntraeger wrote: >>> On 20.11.20 17:01, Eric Farman wrote: >>>> A Linux binary will have the string "S390EP" at address 0x10008, >>>> which is important in getting the guest up off the ground. In the >>>> case of a reboot (specifically chreipl going to a new device), >>>> we should defer to the PSW at address zero for the new config, >>>> which will re-write "S390EP" from the new image. >>>> >>>> Let's clear it out at this point so that a reipl to, say, a DASD >>>> passthrough device drives the IPL path from scratch without disrupting >>>> disrupting the order of operations for other boots. >>>> >>>> Rather than hardcoding the address of this magic (again), let's >>>> define it somewhere so that the two users are visibly related. >>> >>> >>> Hmmm, this might have side effects, e.g. if you do something like a kdump >>> or kexec to a non-Linux binary that happens to have code at 0x10008, no? >> >> Do these scenarios really go through the s390-ccw bios again, or do they >> rather bypass the bios and jump directly into the new kernel? > > Right they jump directly into the new kernel. So this patch could actually > be "good enough" for 5.2 as is?
I think it should be fine, yes. I'll give it a try with my usual s390-ccw bios tests, and if there are no regressions (and no other objections on the mailing list here), I'll prepare a pull request. Thomas
