On 3/2/21 1:20 PM, Sean Christopherson wrote: > On Tue, Mar 02, 2021, Babu Moger wrote: >> This problem was reported on a SVM guest while executing kexec. >> Kexec fails to load the new kernel when the PCID feature is enabled. >> >> When kexec starts loading the new kernel, it starts the process by >> resetting the vCPU's and then bringing each vCPU online one by one. >> The vCPU reset is supposed to reset all the register states before the >> vCPUs are brought online. However, the CR4 register is not reset during >> this process. If this register is already setup during the last boot, >> all the flags can remain intact. The X86_CR4_PCIDE bit can only be >> enabled in long mode. So, it must be enabled much later in SMP >> initialization. Having the X86_CR4_PCIDE bit set during SMP boot can >> cause a boot failures. >> >> Fix the issue by resetting the CR4 register in init_vmcb(). >> >> Signed-off-by: Babu Moger <babu.moger@xxxxxxx> > > Cc: stable@xxxxxxxxxxxxxxx > > The bug goes back too far to have a meaningful Fixes. > > Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx> Sean, Thanks > > > On a related topic, I think we can clean up the RESET/INIT flows by hoisting the > common code into kvm_vcpu_reset(). That would also provide good motivation for > removing the init_vmcb() call in svm_create_vcpu(), which is fully redundant > with the call in svm_vcpu_reset(). I'll put that on the todo list. Yes.Please.Thought about cleaning init_vmcb and svm_vcpu_reset little bit. That will require some more tests and review. We didn't want to delay the fix for that now. Thanks Babu
