On 2023-03-15 15:48:53, Michael Ellerman wrote: > Kautuk Consul <kcon...@linux.vnet.ibm.com> writes: > > kvmppc_hv_entry is called from only 2 locations within > > book3s_hv_rmhandlers.S. Both of those locations set r4 > > as HSTATE_KVM_VCPU(r13) before calling kvmppc_hv_entry. > > So, shift the r4 load instruction to kvmppc_hv_entry and > > thus modify the calling convention of this function. > > > > Signed-off-by: Kautuk Consul <kcon...@linux.vnet.ibm.com> > > --- > > arch/powerpc/kvm/book3s_hv_rmhandlers.S | 9 ++++----- > > 1 file changed, 4 insertions(+), 5 deletions(-) > > > > diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S > > b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > > index b81ba4ee0521..da9a15db12fe 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 > > Where did this barrier go? > > I don't see that it's covered by any existing barriers in > kvmppc_hv_entry, and you don't add it back anywhere.
My concept about this is that since now the call to kvmppc_hv_entry is first taken before the load to r4 shouldn't the pending load in the pipeline of the HSTATE_KVM_VCORE as per the earlier comment be ordered anyway before-hand ? Or do you mesn to say that pending loads may not be cleared/flushed across the "bl <funcname>" boundary ? > > > - 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 +521,8 @@ SYM_INNER_LABEL(kvmppc_hv_entry, SYM_L_LOCAL) > > li r6, KVM_GUEST_MODE_HOST_HV > > stb r6, HSTATE_IN_GUEST(r13) > > > > + ld r4, HSTATE_KVM_VCPU(r13) > > + > > #ifdef CONFIG_KVM_BOOK3S_HV_P8_TIMING > > /* Store initial timestamp */ > > cmpdi r4, 0 > > cheers
