From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id 74409C433EF for ; Fri, 4 Feb 2022 16:01:16 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id CACFD40FAA; Fri, 4 Feb 2022 11:01:15 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id JGb7cxtbtzx6; Fri, 4 Feb 2022 11:01:14 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 64ECD40FD3; Fri, 4 Feb 2022 11:01:14 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B299440AFA for ; Fri, 4 Feb 2022 11:01:13 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 23619mYeP0je for ; Fri, 4 Feb 2022 11:01:08 -0500 (EST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 1BCD540C2B for ; Fri, 4 Feb 2022 11:01:08 -0500 (EST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7C8511396; Fri, 4 Feb 2022 08:01:07 -0800 (PST) Received: from monolith.localdoman (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 54B503F718; Fri, 4 Feb 2022 08:01:04 -0800 (PST) Date: Fri, 4 Feb 2022 16:01:13 +0000 From: Alexandru Elisei To: Marc Zyngier Subject: Re: [PATCH v6 22/64] KVM: arm64: nv: Respect virtual HCR_EL2.TWX setting Message-ID: References: <20220128121912.509006-1-maz@kernel.org> <20220128121912.509006-23-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Cc: kernel-team@android.com, kvm@vger.kernel.org, Andre Przywara , Christoffer Dall , Chase Conklin , kvmarm@lists.cs.columbia.edu, mihai.carabas@oracle.com, Ganapatrao Kulkarni , "Russell King \(Oracle\)" , linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi, On Fri, Feb 04, 2022 at 03:40:15PM +0000, Alexandru Elisei wrote: > Hi Marc, > > On Fri, Jan 28, 2022 at 12:18:30PM +0000, Marc Zyngier wrote: > > From: Jintack Lim > > > > Forward exceptions due to WFI or WFE instructions to the virtual EL2 if > > they are not coming from the virtual EL2 and virtual HCR_EL2.TWX is set. > > > > Signed-off-by: Jintack Lim > > Signed-off-by: Marc Zyngier > > --- > > arch/arm64/include/asm/kvm_nested.h | 2 ++ > > arch/arm64/kvm/Makefile | 2 +- > > arch/arm64/kvm/handle_exit.c | 11 ++++++++++- > > arch/arm64/kvm/nested.c | 28 ++++++++++++++++++++++++++++ > > 4 files changed, 41 insertions(+), 2 deletions(-) > > create mode 100644 arch/arm64/kvm/nested.c > > > > diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h > > index 5a85be6d8eb3..79d382fa02ea 100644 > > --- a/arch/arm64/include/asm/kvm_nested.h > > +++ b/arch/arm64/include/asm/kvm_nested.h > > @@ -65,4 +65,6 @@ static inline u64 translate_cnthctl_el2_to_cntkctl_el1(u64 cnthctl) > > (cnthctl & (CNTHCTL_EVNTI | CNTHCTL_EVNTDIR | CNTHCTL_EVNTEN))); > > } > > > > +int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe); > > + > > #endif /* __ARM64_KVM_NESTED_H */ > > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile > > index b67c4ebd72b1..dbaf42ff65f1 100644 > > --- a/arch/arm64/kvm/Makefile > > +++ b/arch/arm64/kvm/Makefile > > @@ -14,7 +14,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \ > > inject_fault.o va_layout.o handle_exit.o \ > > guest.o debug.o reset.o sys_regs.o \ > > vgic-sys-reg-v3.o fpsimd.o pmu.o pkvm.o \ > > - arch_timer.o trng.o emulate-nested.o \ > > + arch_timer.o trng.o emulate-nested.o nested.o \ > > vgic/vgic.o vgic/vgic-init.o \ > > vgic/vgic-irqfd.o vgic/vgic-v2.o \ > > vgic/vgic-v3.o vgic/vgic-v4.o \ > > diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > > index 0cedef6e0d80..a1b1bbf3d598 100644 > > --- a/arch/arm64/kvm/handle_exit.c > > +++ b/arch/arm64/kvm/handle_exit.c > > @@ -119,7 +119,16 @@ static int handle_no_fpsimd(struct kvm_vcpu *vcpu) > > */ > > static int kvm_handle_wfx(struct kvm_vcpu *vcpu) > > { > > - if (kvm_vcpu_get_esr(vcpu) & ESR_ELx_WFx_ISS_WFE) { > > + bool is_wfe = !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_WFx_ISS_WFE); > > + > > + if (vcpu_has_nv(vcpu)) { > > + int ret = handle_wfx_nested(vcpu, is_wfe); > > + > > + if (ret != -EINVAL) > > + return ret; > > I find this rather clunky. The common pattern is that a function returns > early when it encounters an error, but here this pattern is reversed: > -EINVAL means that handle_wfx_nested() failed in handling the WFx, so > proceed as usual; conversly, anything but -EINVAL means handle_wfx_nested() > was successful in handling WFx, so exit early from kvm_handle_wfx(). > > That would be ok by itself, but if we dig deeper, handle_wfx_nested() ends up > calling kvm_inject_nested(), where -EINVAL is actually an error code. Granted, > that should never happen, because kvm_handle_wfx() first checks vcpu_has_nv(), > but still feels like something that could be improved. > > Maybe changing handle_wfx_nested() like this would be better: > [..] Or change kvm_handle_wfx() to handle the WFx trap like kvm_handle_fpasimd(): if (guest_wfx_traps_enabled(vcpu)) return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu)); Thanks, Alex _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm