| Message ID | 20170529101218.GC13938@fergus.ozlabs.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 2017-05-29 at 20:12 +1000, Paul Mackerras wrote: > This allows userspace (e.g. QEMU) to enable large decrementer mode > for > the guest when running on a POWER9 host, by setting the LPCR_LD bit > in > the guest LPCR value. With this, the guest exit code saves 64 bits > of > the guest DEC value on exit. Other places that use the guest DEC > value check the LPCR_LD bit in the guest LPCR value, and if it is > set, > omit the 32-bit sign extension that would otherwise be done. > > This doesn't change the DEC emulation used by PR KVM because PR KVM > is not supported on POWER9 yet. > > This is partly based on an earlier patch by Oliver O'Halloran. > > Signed-off-by: Paul Mackerras <paulus@ozlabs.org> Tested with a hacked up qemu and upstream guest/host (with these patches). Tested-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com> > --- > arch/powerpc/include/asm/kvm_host.h | 2 +- > arch/powerpc/kvm/book3s_hv.c | 6 ++++++ > arch/powerpc/kvm/book3s_hv_rmhandlers.S | 29 > ++++++++++++++++++++++++----- > arch/powerpc/kvm/emulate.c | 4 ++-- > 4 files changed, 33 insertions(+), 8 deletions(-) > > diff --git a/arch/powerpc/include/asm/kvm_host.h > b/arch/powerpc/include/asm/kvm_host.h > index 9c51ac4..3f879c8 100644 > --- a/arch/powerpc/include/asm/kvm_host.h > +++ b/arch/powerpc/include/asm/kvm_host.h > @@ -579,7 +579,7 @@ struct kvm_vcpu_arch { > ulong mcsrr0; > ulong mcsrr1; > ulong mcsr; > - u32 dec; > + ulong dec; > #ifdef CONFIG_BOOKE > u32 decar; > #endif > diff --git a/arch/powerpc/kvm/book3s_hv.c > b/arch/powerpc/kvm/book3s_hv.c > index 42b7a4f..9b2eb66 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -1143,6 +1143,12 @@ static void kvmppc_set_lpcr(struct kvm_vcpu > *vcpu, u64 new_lpcr, > mask = LPCR_DPFD | LPCR_ILE | LPCR_TC; > if (cpu_has_feature(CPU_FTR_ARCH_207S)) > mask |= LPCR_AIL; > + /* > + * On POWER9, allow userspace to enable large decrementer > for the > + * guest, whether or not the host has it enabled. > + */ > + if (cpu_has_feature(CPU_FTR_ARCH_300)) > + mask |= LPCR_LD; > > /* Broken 32-bit version of LPCR must not clear top bits */ > if (preserve_top32) > diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S > b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > index e390b38..3c901b5 100644 > --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S > +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > @@ -920,7 +920,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300) > mftb r7 > subf r3,r7,r8 > mtspr SPRN_DEC,r3 > - stw r3,VCPU_DEC(r4) > + std r3,VCPU_DEC(r4) > > ld r5, VCPU_SPRG0(r4) > ld r6, VCPU_SPRG1(r4) > @@ -1032,7 +1032,13 @@ kvmppc_cede_reentry: /* r4 = > vcpu, r13 = paca */ > li r0, BOOK3S_INTERRUPT_EXTERNAL > bne cr1, 12f > mfspr r0, SPRN_DEC > - cmpwi r0, 0 > +BEGIN_FTR_SECTION > + /* On POWER9 check whether the guest has large decrementer > enabled */ > + andis. r8, r8, LPCR_LD@h > + bne 15f > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) > + extsw r0, r0 > +15: cmpdi r0, 0 > li r0, BOOK3S_INTERRUPT_DECREMENTER > bge 5f > > @@ -1459,12 +1465,18 @@ mc_cont: > mtspr SPRN_SPURR,r4 > > /* Save DEC */ > + ld r3, HSTATE_KVM_VCORE(r13) > mfspr r5,SPRN_DEC > mftb r6 > + /* On P9, if the guest has large decr enabled, don't sign > extend */ > +BEGIN_FTR_SECTION > + ld r4, VCORE_LPCR(r3) > + andis. r4, r4, LPCR_LD@h > + bne 16f > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) > extsw r5,r5 > - add r5,r5,r6 > +16: add r5,r5,r6 > /* r5 is a guest timebase value here, convert to host TB */ > - ld r3,HSTATE_KVM_VCORE(r13) > ld r4,VCORE_TB_OFFSET(r3) > subf r5,r4,r5 > std r5,VCPU_DEC_EXPIRES(r9) > @@ -2376,8 +2388,15 @@ END_FTR_SECTION_IFSET(CPU_FTR_TM) > mfspr r3, SPRN_DEC > mfspr r4, SPRN_HDEC > mftb r5 > +BEGIN_FTR_SECTION > + /* On P9 check whether the guest has large decrementer mode > enabled */ > + ld r6, HSTATE_KVM_VCORE(r13) > + ld r6, VCORE_LPCR(r6) > + andis. r6, r6, LPCR_LD@h > + bne 68f > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) > extsw r3, r3 > - EXTEND_HDEC(r4) > +68: EXTEND_HDEC(r4) > cmpd r3, r4 > ble 67f > mtspr SPRN_DEC, r4 > diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c > index c873ffe..4d8b4d6 100644 > --- a/arch/powerpc/kvm/emulate.c > +++ b/arch/powerpc/kvm/emulate.c > @@ -39,7 +39,7 @@ void kvmppc_emulate_dec(struct kvm_vcpu *vcpu) > unsigned long dec_nsec; > unsigned long long dec_time; > > - pr_debug("mtDEC: %x\n", vcpu->arch.dec); > + pr_debug("mtDEC: %lx\n", vcpu->arch.dec); > hrtimer_try_to_cancel(&vcpu->arch.dec_timer); > > #ifdef CONFIG_PPC_BOOK3S > @@ -109,7 +109,7 @@ static int kvmppc_emulate_mtspr(struct kvm_vcpu > *vcpu, int sprn, int rs) > case SPRN_TBWU: break; > > case SPRN_DEC: > - vcpu->arch.dec = spr_val; > + vcpu->arch.dec = (u32) spr_val; > kvmppc_emulate_dec(vcpu); > break; >
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 9c51ac4..3f879c8 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -579,7 +579,7 @@ struct kvm_vcpu_arch { ulong mcsrr0; ulong mcsrr1; ulong mcsr; - u32 dec; + ulong dec; #ifdef CONFIG_BOOKE u32 decar; #endif diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 42b7a4f..9b2eb66 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1143,6 +1143,12 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr, mask = LPCR_DPFD | LPCR_ILE | LPCR_TC; if (cpu_has_feature(CPU_FTR_ARCH_207S)) mask |= LPCR_AIL; + /* + * On POWER9, allow userspace to enable large decrementer for the + * guest, whether or not the host has it enabled. + */ + if (cpu_has_feature(CPU_FTR_ARCH_300)) + mask |= LPCR_LD; /* Broken 32-bit version of LPCR must not clear top bits */ if (preserve_top32) diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index e390b38..3c901b5 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -920,7 +920,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300) mftb r7 subf r3,r7,r8 mtspr SPRN_DEC,r3 - stw r3,VCPU_DEC(r4) + std r3,VCPU_DEC(r4) ld r5, VCPU_SPRG0(r4) ld r6, VCPU_SPRG1(r4) @@ -1032,7 +1032,13 @@ kvmppc_cede_reentry: /* r4 = vcpu, r13 = paca */ li r0, BOOK3S_INTERRUPT_EXTERNAL bne cr1, 12f mfspr r0, SPRN_DEC - cmpwi r0, 0 +BEGIN_FTR_SECTION + /* On POWER9 check whether the guest has large decrementer enabled */ + andis. r8, r8, LPCR_LD@h + bne 15f +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) + extsw r0, r0 +15: cmpdi r0, 0 li r0, BOOK3S_INTERRUPT_DECREMENTER bge 5f @@ -1459,12 +1465,18 @@ mc_cont: mtspr SPRN_SPURR,r4 /* Save DEC */ + ld r3, HSTATE_KVM_VCORE(r13) mfspr r5,SPRN_DEC mftb r6 + /* On P9, if the guest has large decr enabled, don't sign extend */ +BEGIN_FTR_SECTION + ld r4, VCORE_LPCR(r3) + andis. r4, r4, LPCR_LD@h + bne 16f +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) extsw r5,r5 - add r5,r5,r6 +16: add r5,r5,r6 /* r5 is a guest timebase value here, convert to host TB */ - ld r3,HSTATE_KVM_VCORE(r13) ld r4,VCORE_TB_OFFSET(r3) subf r5,r4,r5 std r5,VCPU_DEC_EXPIRES(r9) @@ -2376,8 +2388,15 @@ END_FTR_SECTION_IFSET(CPU_FTR_TM) mfspr r3, SPRN_DEC mfspr r4, SPRN_HDEC mftb r5 +BEGIN_FTR_SECTION + /* On P9 check whether the guest has large decrementer mode enabled */ + ld r6, HSTATE_KVM_VCORE(r13) + ld r6, VCORE_LPCR(r6) + andis. r6, r6, LPCR_LD@h + bne 68f +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) extsw r3, r3 - EXTEND_HDEC(r4) +68: EXTEND_HDEC(r4) cmpd r3, r4 ble 67f mtspr SPRN_DEC, r4 diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c index c873ffe..4d8b4d6 100644 --- a/arch/powerpc/kvm/emulate.c +++ b/arch/powerpc/kvm/emulate.c @@ -39,7 +39,7 @@ void kvmppc_emulate_dec(struct kvm_vcpu *vcpu) unsigned long dec_nsec; unsigned long long dec_time; - pr_debug("mtDEC: %x\n", vcpu->arch.dec); + pr_debug("mtDEC: %lx\n", vcpu->arch.dec); hrtimer_try_to_cancel(&vcpu->arch.dec_timer); #ifdef CONFIG_PPC_BOOK3S @@ -109,7 +109,7 @@ static int kvmppc_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs) case SPRN_TBWU: break; case SPRN_DEC: - vcpu->arch.dec = spr_val; + vcpu->arch.dec = (u32) spr_val; kvmppc_emulate_dec(vcpu); break;
This allows userspace (e.g. QEMU) to enable large decrementer mode for the guest when running on a POWER9 host, by setting the LPCR_LD bit in the guest LPCR value. With this, the guest exit code saves 64 bits of the guest DEC value on exit. Other places that use the guest DEC value check the LPCR_LD bit in the guest LPCR value, and if it is set, omit the 32-bit sign extension that would otherwise be done. This doesn't change the DEC emulation used by PR KVM because PR KVM is not supported on POWER9 yet. This is partly based on an earlier patch by Oliver O'Halloran. Signed-off-by: Paul Mackerras <paulus@ozlabs.org> --- arch/powerpc/include/asm/kvm_host.h | 2 +- arch/powerpc/kvm/book3s_hv.c | 6 ++++++ arch/powerpc/kvm/book3s_hv_rmhandlers.S | 29 ++++++++++++++++++++++++----- arch/powerpc/kvm/emulate.c | 4 ++-- 4 files changed, 33 insertions(+), 8 deletions(-)