Messages in this thread | | | Date | Tue, 21 Mar 2023 14:07:22 +0530 | From | Kautuk Consul <> | Subject | Re: [PATCH v3 2/2] arch/powerpc/kvm: kvmppc_hv_entry: remove r4 argument |
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On 2023-03-21 10:24:36, Kautuk Consul wrote: > > Is r4 there only used for CONFIG_KVM_BOOK3S_HV_P8_TIMING? Could put it > > under there. Although you then lose the barrier if it's disabled, that > > is okay if you're sure that's the only memory operation being ordered. > r4 is also used by the secondary_too_late label. So I decided against > moving it inside the CONFIG_KVM_BOOK3S_HV_P8_TIMING #ifdef as then I > would need to again load from HSTATE_KVM_VCPU(r13) in secondary_too_late. > > Sorry, forgot to mention, r4 is also being used in the 10f label. Thats one more reason to not shift the r4 load into the #ifdef. > > I'm not sure how much new work we want to put into changing this asm > > code, since it's POWER7/8 only. I would love to move this (and the > > other) KVM implementations to C like we did with P9. It's a pretty big > > job though. > Yeah. I was just reviewing this code and decided to send this small > improvement to the mailing list. I will check with my team and ask > them if we could move this implementation to C. > > > > Thanks, > > Nick > > > > > > > > Signed-off-by: Kautuk Consul <kconsul@linux.vnet.ibm.com> > > > --- > > > arch/powerpc/kvm/book3s_hv_rmhandlers.S | 11 ++++++----- > > > 1 file changed, 6 insertions(+), 5 deletions(-) > > > > > > diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > > > index b81ba4ee0521..b61f0b2c677b 100644 > > > --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S > > > +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > > > @@ -85,7 +85,7 @@ _GLOBAL_TOC(kvmppc_hv_entry_trampoline) > > > RFI_TO_KERNEL > > > > > > kvmppc_call_hv_entry: > > > - ld r4, HSTATE_KVM_VCPU(r13) > > > + /* Enter guest. */ > > > bl kvmppc_hv_entry > > > > > > /* Back from guest - restore host state and return to caller */ > > > @@ -352,9 +352,7 @@ kvm_secondary_got_guest: > > > mtspr SPRN_LDBAR, r0 > > > isync > > > 63: > > > - /* Order load of vcpu after load of vcore */ > > > - lwsync > > > - ld r4, HSTATE_KVM_VCPU(r13) > > > + /* Enter guest. */ > > > bl kvmppc_hv_entry > > > > > > /* Back from the guest, go back to nap */ > > > @@ -506,7 +504,6 @@ SYM_INNER_LABEL(kvmppc_hv_entry, SYM_L_LOCAL) > > > > > > /* Required state: > > > * > > > - * R4 = vcpu pointer (or NULL) > > > * MSR = ~IR|DR > > > * R13 = PACA > > > * R1 = host R1 > > > @@ -524,6 +521,10 @@ SYM_INNER_LABEL(kvmppc_hv_entry, SYM_L_LOCAL) > > > li r6, KVM_GUEST_MODE_HOST_HV > > > stb r6, HSTATE_IN_GUEST(r13) > > > > > > + /* Order load of vcpu after load of vcore */ > > > + lwsync > > > + ld r4, HSTATE_KVM_VCPU(r13) > > > + > > > #ifdef CONFIG_KVM_BOOK3S_HV_P8_TIMING > > > /* Store initial timestamp */ > > > cmpdi r4, 0 > > > -- > > > 2.39.2 > >
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