On Fri, Sep 22, 2017 at 10:46:36AM +0200, Paolo Bonzini wrote: > On 15/09/2017 07:26, Michael Neuling wrote: > > On POWER9 DD2.1 and below, sometimes on a Hypervisor Data Storage > > Interrupt (HDSI) the HDSISR is not be updated at all. > > > > To work around this we put a canary value into the HDSISR before > > returning to a guest and then check for this canary when we take a > > HDSI. If we find the canary on a HDSI, we know the hardware didn't > > update the HDSISR. In this case we return to the guest to retake the > > HDSI which should correctly update the HDSISR the second time HDSI > > entry. > > > > After talking to Paulus we've applied this workaround to all POWER9 > > CPUs. The workaround of returning to the guest shouldn't ever be > > triggered on well behaving CPU. The extra instructions should have > > negligible performance impact. > > > > Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx> > > --- > > arch/powerpc/kvm/book3s_hv_rmhandlers.S | 14 +++++++++++++- > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > > index 663a4a861e..70dca60569 100644 > > --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S > > +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > > @@ -1118,6 +1118,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) > > BEGIN_FTR_SECTION > > mtspr SPRN_PPR, r0 > > END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) > > + > > +/* Move canary into DSISR to check for later */ > > +BEGIN_FTR_SECTION > > + li r0, 0x7fff > > + mtspr SPRN_HDSISR, r0 > > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) > > + > > ld r0, VCPU_GPR(R0)(r4) > > ld r4, VCPU_GPR(R4)(r4) > > > > @@ -1947,9 +1954,14 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX) > > kvmppc_hdsi: > > ld r3, VCPU_KVM(r9) > > lbz r0, KVM_RADIX(r3) > > - cmpwi r0, 0 > > mfspr r4, SPRN_HDAR > > mfspr r6, SPRN_HDSISR > > +BEGIN_FTR_SECTION > > + /* Look for DSISR canary. If we find it, retry instruction */ > > + cmpdi r6, 0x7fff > > + beq 6f > > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) > > + cmpwi r0, 0 > > bne .Lradix_hdsi /* on radix, just save DAR/DSISR/ASDR */ > > /* HPTE not found fault or protection fault? */ > > andis. r0, r6, (DSISR_NOHPTE | DSISR_PROTFAULT)@h > > > > Applied to kvm/master, thanks. I'm not seeing it; have you pushed out the tree? -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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