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. 
 
> -     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

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