On 06/16/15 07:47, Marc Zyngier wrote: > On 16/06/15 13:30, Vikram Sethi wrote: >> On 06/16/15 01:46, Marc Zyngier wrote: >>> On Tue, 16 Jun 2015 02:34:23 +0100 >>> Vikram Sethi <vikrams@xxxxxxxxxxxxxx> wrote: >>> >>> Hi Vikram, >>> >>>> Hi Marc, Christoffer, Catalin, Will, >>>> >>>> I'm seeing an issue with KVM HCPTR (cp15) writes on guest entry/exit >>>> on one of Qualcomm's CPU cores in AArch32 host and AArch32 guest >>>> mode. Our CPU architects believe that HCPTR cp15 writes are context >>>> changing and require an isb. With an isb in set_hcptr macro in >>>> arch/arm/kvm/interrupts_head.S I am able to boot the Aarch32 guest, >>>> but without it, I see strange crashes to hyp_undef or hyp_pabt. >>> [...] >>> >>> Can you look at the following patch (queued for 4.2)? >>> >>> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/330955.html >>> >>> Please let me know if this solves the issue you are seeing. >> Don't we have the same issue the first time guest touches FP and >> traps i.e in switch_to_guest_vfp where we turn on floating point >> access in HCPTR and immediately access FPEXC in store_vfp_state >> without a isb? > Good point, looks like my initial fix is incomplete. I'll repost a more > complete fix but in the meantime, does adding the following work for you? Yes, the additional isb in switch_to_guest_vfp along with your original patch works for me. When you refactor the original patch will it be cleaner to handle the isb in the set_hcptr macro whenever it is changed to not trap VFP access? > > diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S > index 3ac7aca..5b30047 100644 > --- a/arch/arm/kvm/interrupts.S > +++ b/arch/arm/kvm/interrupts.S > @@ -487,6 +487,7 @@ switch_to_guest_vfp: > > @ NEON/VFP used. Turn on VFP access. > set_hcptr vmexit, (HCPTR_TCP(10) | HCPTR_TCP(11)) > + isb @ Force execution of HCPTR as we've just reenabled VFP access > > @ Switch VFP/NEON hardware state to the guest's > add r7, r0, #VCPU_VFP_HOST > > Thanks, > > M. -- Vikram Sethi Qualcomm Technologies Inc, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
