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Tue, 23 Nov 2021 01:54:00 -0800 (PST) Received: from bobo.ibm.com ([124.170.11.53]) by smtp.gmail.com with ESMTPSA id j8sm12662176pfc.8.2021.11.23.01.53.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Nov 2021 01:53:59 -0800 (PST) From: Nicholas Piggin To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v4 36/53] KVM: PPC: Book3S HV P9: Demand fault EBB facility registers Date: Tue, 23 Nov 2021 19:52:14 +1000 Message-Id: <20211123095231.1036501-37-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20211123095231.1036501-1-npiggin@gmail.com> References: <20211123095231.1036501-1-npiggin@gmail.com> MIME-Version: 1.0 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nicholas Piggin , Fabiano Rosas Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Use HFSCR facility disabling to implement demand faulting for EBB, with a hysteresis counter similar to the load_fp etc counters in context switching that implement the equivalent demand faulting for userspace facilities. This speeds up guest entry/exit by avoiding the register save/restore when a guest is not frequently using them. When a guest does use them often, there will be some additional demand fault overhead, but these are not commonly used facilities. Reviewed-by: Fabiano Rosas Signed-off-by: Nicholas Piggin --- arch/powerpc/include/asm/kvm_host.h | 1 + arch/powerpc/kvm/book3s_hv.c | 16 +++++++++++++-- arch/powerpc/kvm/book3s_hv_p9_entry.c | 28 +++++++++++++++++++++------ 3 files changed, 37 insertions(+), 8 deletions(-) diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 21ca15c3bc0b..7a55b19eb6c0 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -579,6 +579,7 @@ struct kvm_vcpu_arch { ulong cfar; ulong ppr; u32 pspb; + u8 load_ebb; ulong fscr; ulong shadow_fscr; ulong ebbhr; diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 3795080d5403..da29cf9236c8 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1436,6 +1436,16 @@ static int kvmppc_pmu_unavailable(struct kvm_vcpu *vcpu) return RESUME_GUEST; } +static int kvmppc_ebb_unavailable(struct kvm_vcpu *vcpu) +{ + if (!(vcpu->arch.hfscr_permitted & HFSCR_EBB)) + return EMULATE_FAIL; + + vcpu->arch.hfscr |= HFSCR_EBB; + + return RESUME_GUEST; +} + static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu, struct task_struct *tsk) { @@ -1727,6 +1737,8 @@ static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu, r = kvmppc_emulate_doorbell_instr(vcpu); if (cause == FSCR_PM_LG) r = kvmppc_pmu_unavailable(vcpu); + if (cause == FSCR_EBB_LG) + r = kvmppc_ebb_unavailable(vcpu); } if (r == EMULATE_FAIL) { kvmppc_core_queue_program(vcpu, SRR1_PROGILL); @@ -2771,9 +2783,9 @@ static int kvmppc_core_vcpu_create_hv(struct kvm_vcpu *vcpu) vcpu->arch.hfscr_permitted = vcpu->arch.hfscr; /* - * PM is demand-faulted so start with it clear. + * PM, EBB is demand-faulted so start with it clear. */ - vcpu->arch.hfscr &= ~HFSCR_PM; + vcpu->arch.hfscr &= ~(HFSCR_PM | HFSCR_EBB); kvmppc_mmu_book3s_hv_init(vcpu); diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c b/arch/powerpc/kvm/book3s_hv_p9_entry.c index a23f09fa7d2d..929a7c336b09 100644 --- a/arch/powerpc/kvm/book3s_hv_p9_entry.c +++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c @@ -232,9 +232,12 @@ static void load_spr_state(struct kvm_vcpu *vcpu, struct p9_host_os_sprs *host_os_sprs) { mtspr(SPRN_TAR, vcpu->arch.tar); - mtspr(SPRN_EBBHR, vcpu->arch.ebbhr); - mtspr(SPRN_EBBRR, vcpu->arch.ebbrr); - mtspr(SPRN_BESCR, vcpu->arch.bescr); + + if (vcpu->arch.hfscr & HFSCR_EBB) { + mtspr(SPRN_EBBHR, vcpu->arch.ebbhr); + mtspr(SPRN_EBBRR, vcpu->arch.ebbrr); + mtspr(SPRN_BESCR, vcpu->arch.bescr); + } if (cpu_has_feature(CPU_FTR_P9_TIDR)) mtspr(SPRN_TIDR, vcpu->arch.tid); @@ -265,9 +268,22 @@ static void load_spr_state(struct kvm_vcpu *vcpu, static void store_spr_state(struct kvm_vcpu *vcpu) { vcpu->arch.tar = mfspr(SPRN_TAR); - vcpu->arch.ebbhr = mfspr(SPRN_EBBHR); - vcpu->arch.ebbrr = mfspr(SPRN_EBBRR); - vcpu->arch.bescr = mfspr(SPRN_BESCR); + + if (vcpu->arch.hfscr & HFSCR_EBB) { + vcpu->arch.ebbhr = mfspr(SPRN_EBBHR); + vcpu->arch.ebbrr = mfspr(SPRN_EBBRR); + vcpu->arch.bescr = mfspr(SPRN_BESCR); + /* + * This is like load_fp in context switching, turn off the + * facility after it wraps the u8 to try avoiding saving + * and restoring the registers each partition switch. + */ + if (!vcpu->arch.nested) { + vcpu->arch.load_ebb++; + if (!vcpu->arch.load_ebb) + vcpu->arch.hfscr &= ~HFSCR_EBB; + } + } if (cpu_has_feature(CPU_FTR_P9_TIDR)) vcpu->arch.tid = mfspr(SPRN_TIDR);