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Tue, 29 Apr 2025 14:49:38 +0100 Date: Tue, 29 Apr 2025 14:49:37 +0100 Message-ID: <86h627hyby.wl-maz@kernel.org> From: Marc Zyngier To: Ben Horgan Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Joey Gouly , Suzuki K Poulose , Oliver Upton , Zenghui Yu , Mark Rutland , Fuad Tabba , Will Deacon , Catalin Marinas Subject: Re: [PATCH v3 24/42] KVM: arm64: Unconditionally configure fine-grain traps In-Reply-To: <363383a2-c05e-458c-82b7-acc6e5d73939@arm.com> References: <20250426122836.3341523-1-maz@kernel.org> <20250426122836.3341523-25-maz@kernel.org> <363383a2-c05e-458c-82b7-acc6e5d73939@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: ben.horgan@arm.com, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, joey.gouly@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, yuzenghui@huawei.com, mark.rutland@arm.com, tabba@google.com, will@kernel.org, catalin.marinas@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Tue, 29 Apr 2025 14:08:27 +0100, Ben Horgan wrote: > > Hi Marc, > > On 4/26/25 13:28, Marc Zyngier wrote: > > From: Mark Rutland > > > > ... otherwise we can inherit the host configuration if this differs from > > the KVM configuration. > > > > Signed-off-by: Mark Rutland > > [maz: simplified a couple of things] > > Signed-off-by: Marc Zyngier > > --- > > arch/arm64/kvm/hyp/include/hyp/switch.h | 39 ++++++++++--------------- > > 1 file changed, 15 insertions(+), 24 deletions(-) > > > > diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h > > index 027d05f308f75..925a3288bd5be 100644 > > --- a/arch/arm64/kvm/hyp/include/hyp/switch.h > > +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h > > @@ -107,7 +107,8 @@ static inline void __activate_traps_fpsimd32(struct kvm_vcpu *vcpu) > > [...] > > static inline void __deactivate_traps_hfgxtr(struct kvm_vcpu > > *vcpu) > > { > > struct kvm_cpu_context *hctxt = host_data_ptr(host_ctxt); > > - struct kvm *kvm = kern_hyp_va(vcpu->kvm); > > if (!cpus_have_final_cap(ARM64_HAS_FGT)) > > return; > > - __deactivate_fgt(hctxt, vcpu, kvm, HFGRTR_EL2); > > - if (cpus_have_final_cap(ARM64_WORKAROUND_AMPERE_AC03_CPU_38)) > Don't we need to continue considering the ampere errata here? Or, at > least worth a mention in the commit message. The FGT registers are always context switched, so whatever was saved *before* the workaround was applied in __activate_traps_hfgxtr() is blindly restored... > > - write_sysreg_s(ctxt_sys_reg(hctxt, HFGWTR_EL2), SYS_HFGWTR_EL2); ... and this write always happens. M. -- Without deviation from the norm, progress is not possible.