On 2017/11/10 2:14, James Morse wrote: > Hi guys, > > On 19/10/17 15:57, James Morse wrote: >> Known issues: > [...] >> * KVM-Migration: VDISR_EL2 is exposed to userspace as DISR_EL1, but how should >> HCR_EL2.VSE or VSESR_EL2 be migrated when the guest has an SError pending but >> hasn't taken it yet...? > > I've been trying to work out how this pending-SError-migration could work. Hi James, I have finished the Qemu part development about RAS and sent the patches out, I think the solution followed your suggestion and other people's suggestion in the mail discussion. For example, not pass KVM exception information to Qemu, according to the SIGBUS type(BUS_MCEERR_AR or BUS_MCEERR_A0) to use different notification type, create guest APEI table and record CPER in rumtime for guest, etc how about you have a look at these implementation and then we discuss this migration again? thanks. > > If HCR_EL2.VSE is set then the guest will take a virtual SError when it next > unmasks SError. Today this doesn't get migrated, but only KVM sets this bit as > an attempt to kill the guest. > > This will be more of a problem with GengDongjiu's SError CAP for triggering > guest SError from user-space, which will also allow the VSESR_EL2 to be > specified. (this register becomes the guest ESR_EL1 when the virtual SError is > taken and is used to emulate firmware-first's NOTIFY_SEI and eventually > kernel-first RAS). These errors are likely to be handled by the guest. > > > We don't want to expose VSESR_EL2 to user-space, and for migration it isn't > enough as a value of '0' doesn't tell us if HCR_EL2.VSE is set. > > To get out of this corner: why not declare pending-SError-migration an invalid > thing to do? > > We can give Qemu a way to query if a virtual SError is (still) pending. Qemu > would need to check this on each vcpu after migration, just before it throws the > switch and the guest runs on the new host. This way the VSESR_EL2 value doesn't > need migrating at all. > > In the ideal world, Qemu could re-inject the last SError it triggered if there > is still one pending when it migrates... but because KVM injects errors too, it > would need to block migration until this flag is cleared. > KVM can promise this doesn't change unless you run the vcpu, so provided the > vcpu actually takes the SError at some point this thing can still be migrated. > > This does make the VSE machinery hidden unmigratable state in KVM, which is nasty. > > Can anyone suggest a better way? > > > Thanks, > > James > > . > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
