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 X-Spam-Level: X-Spam-Status: No, score=-15.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FDDDC47094 for ; Thu, 10 Jun 2021 16:05:41 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 19E5D60FEA for ; Thu, 10 Jun 2021 16:05:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 19E5D60FEA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=Huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:CC:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=/bxirvCRuQy29u3AscRum0tSrPbaDoI/nNj5H/3KzlE=; b=sayTVJPctCxPGL rWoIlITLy3WCTpVuFP8pJTchARKTOvRdxTZto+AhwICIXkEvTuEnCCmP9Rg3Jbhyr77LMr/GgJGC4 hi89BWQJE3fiFvKA+3K2cpVFLVvNEglDQA19sO7DwwZxALp2yVTOu5K33shJpyMn2zjRoC3bxQm6s RoJsUjASk1ZGzcc9xrbYSgkmPXdA917moLpMkJLLfVh9rMdgiR875+l7yiwNKQAx6od4Np8VuY5hE Ej+iugZ7tY+ZG0dhxn32hfOF8sr7sA+OfCvbyZmiIgukN9ryTQyOR33UGYeSnf3zzzOMWk/i4xKQM AZdg+aUGzrxnxrUx/kgw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lrN9i-001YZe-Su; Thu, 10 Jun 2021 16:03:43 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lrN8l-001YGq-QA for linux-arm-kernel@lists.infradead.org; Thu, 10 Jun 2021 16:02:46 +0000 Received: from fraeml738-chm.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4G17hY43GQz6M4gy; Thu, 10 Jun 2021 23:49:49 +0800 (CST) Received: from lhreml710-chm.china.huawei.com (10.201.108.61) by fraeml738-chm.china.huawei.com (10.206.15.219) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 10 Jun 2021 18:02:39 +0200 Received: from localhost (10.52.126.112) by lhreml710-chm.china.huawei.com (10.201.108.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 10 Jun 2021 17:02:38 +0100 Date: Thu, 10 Jun 2021 17:02:35 +0100 From: Jonathan Cameron To: Jean-Philippe Brucker CC: , , , , , , , , , , , , , , Subject: Re: [RFC PATCH 4/5] KVM: arm64: Pass hypercalls to userspace Message-ID: <20210610170235.00003494@Huawei.com> In-Reply-To: <20210608154805.216869-5-jean-philippe@linaro.org> References: <20210608154805.216869-1-jean-philippe@linaro.org> <20210608154805.216869-5-jean-philippe@linaro.org> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; i686-w64-mingw32) MIME-Version: 1.0 X-Originating-IP: [10.52.126.112] X-ClientProxiedBy: lhreml728-chm.china.huawei.com (10.201.108.79) To lhreml710-chm.china.huawei.com (10.201.108.61) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210610_090244_219430_703F51E5 X-CRM114-Status: GOOD ( 38.86 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 8 Jun 2021 17:48:05 +0200 Jean-Philippe Brucker wrote: > Let userspace request to handle all hypercalls that aren't handled by > KVM, by setting the KVM_CAP_ARM_HVC_TO_USER capability. > > With the help of another capability, this will allow userspace to handle > PSCI calls. > > Suggested-by: James Morse > Signed-off-by: Jean-Philippe Brucker Trivial question inline. > --- > > Notes on this implementation: > > * A similar mechanism was proposed for SDEI some time ago [1]. This RFC > generalizes the idea to all hypercalls, since that was suggested on > the list [2, 3]. > > * We're reusing kvm_run.hypercall. I copied x0-x5 into > kvm_run.hypercall.args[] to help userspace but I'm tempted to remove > this, because: > - Most user handlers will need to write results back into the > registers (x0-x3 for SMCCC), so if we keep this shortcut we should > go all the way and synchronize them on return to kernel. > - QEMU doesn't care about this shortcut, it pulls all vcpu regs before > handling the call. > - SMCCC uses x0-x16 for parameters. > x0 does contain the SMCCC function ID and may be useful for fast > dispatch, we could keep that plus the immediate number. > > * Should we add a flag in the kvm_run.hypercall telling whether this is > HVC or SMC? Can be added later in those bottom longmode and pad > fields. > > * On top of this we could share with userspace which HVC ranges are > available and which ones are handled by KVM. That can actually be > added independently, through a vCPU/VM device attribute (which doesn't > consume a new ioctl): > - userspace issues HAS_ATTR ioctl on the VM fd to query whether this > feature is available. > - userspace queries the number N of HVC ranges using one GET_ATTR. > - userspace passes an array of N ranges using another GET_ATTR. > The array is filled and returned by KVM. > > * Untested for AArch32 guests. > > [1] https://lore.kernel.org/linux-arm-kernel/20170808164616.25949-12-james.morse@arm.com/ > [2] https://lore.kernel.org/linux-arm-kernel/bf7e83f1-c58e-8d65-edd0-d08f27b8b766@arm.com/ > [3] https://lore.kernel.org/linux-arm-kernel/f56cf420-affc-35f0-2355-801a924b8a35@arm.com/ > --- > Documentation/virt/kvm/api.rst | 17 +++++++++++++++-- > arch/arm64/include/asm/kvm_host.h | 1 + > include/kvm/arm_psci.h | 4 ++++ > include/uapi/linux/kvm.h | 1 + > arch/arm64/kvm/arm.c | 5 +++++ > arch/arm64/kvm/hypercalls.c | 28 +++++++++++++++++++++++++++- > 6 files changed, 53 insertions(+), 3 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index e4fe7fb60d5d..3d8c1661e7b2 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -5228,8 +5228,12 @@ to the byte array. > __u32 pad; > } hypercall; > > -Unused. This was once used for 'hypercall to userspace'. To implement > -such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390). > +On x86 this was once used for 'hypercall to userspace'. To implement such > +functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390). > + > +On arm64 it is used for hypercalls, when the KVM_CAP_ARM_HVC_TO_USER capability > +is enabled. 'nr' contains the HVC or SMC immediate. 'args' contains registers > +x0 - x5. The other parameters are unused. > > .. note:: KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO. > > @@ -6894,3 +6898,12 @@ This capability is always enabled. > This capability indicates that the KVM virtual PTP service is > supported in the host. A VMM can check whether the service is > available to the guest on migration. > + > +8.33 KVM_CAP_ARM_HVC_TO_USER > +---------------------------- > + > +:Architecture: arm64 > + > +This capability indicates that KVM can pass unhandled hypercalls to userspace, > +if the VMM enables it. Hypercalls are passed with KVM_EXIT_HYPERCALL in > +kvm_run::hypercall. > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 3ca732feb9a5..25554ce97045 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -123,6 +123,7 @@ struct kvm_arch { > * supported. > */ > bool return_nisv_io_abort_to_user; > + bool hvc_to_user; > > /* > * VM-wide PMU filter, implemented as a bitmap and big enough for > diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h > index 5b58bd2fe088..d6b71a48fbb1 100644 > --- a/include/kvm/arm_psci.h > +++ b/include/kvm/arm_psci.h > @@ -16,6 +16,10 @@ > > #define KVM_ARM_PSCI_LATEST KVM_ARM_PSCI_1_0 > > +#define KVM_PSCI_FN_LAST KVM_PSCI_FN(3) > +#define PSCI_0_2_FN_LAST PSCI_0_2_FN(0x3f) > +#define PSCI_0_2_FN64_LAST PSCI_0_2_FN64(0x3f) Why 3f? Perhaps a spec reference if appropriate. > + > /* > * We need the KVM pointer independently from the vcpu as we can call > * this from HYP, and need to apply kern_hyp_va on it... > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 06ba64c49737..aa831986a399 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -1084,6 +1084,7 @@ struct kvm_ppc_resize_hpt { > #define KVM_CAP_VM_COPY_ENC_CONTEXT_FROM 197 > #define KVM_CAP_PTP_KVM 198 > #define KVM_CAP_ARM_MP_HALTED 199 > +#define KVM_CAP_ARM_HVC_TO_USER 200 > > #ifdef KVM_CAP_IRQ_ROUTING > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index d6ad977fea5f..074197721e97 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -93,6 +93,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > r = 0; > kvm->arch.return_nisv_io_abort_to_user = true; > break; > + case KVM_CAP_ARM_HVC_TO_USER: > + r = 0; > + kvm->arch.hvc_to_user = true; > + break; > default: > r = -EINVAL; > break; > @@ -208,6 +212,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > case KVM_CAP_VCPU_ATTRIBUTES: > case KVM_CAP_PTP_KVM: > case KVM_CAP_ARM_MP_HALTED: > + case KVM_CAP_ARM_HVC_TO_USER: > r = 1; > break; > case KVM_CAP_SET_GUEST_DEBUG2: > diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c > index 30da78f72b3b..ccc2015eddf9 100644 > --- a/arch/arm64/kvm/hypercalls.c > +++ b/arch/arm64/kvm/hypercalls.c > @@ -58,6 +58,28 @@ static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val) > val[3] = lower_32_bits(cycles); > } > > +static int kvm_hvc_user(struct kvm_vcpu *vcpu) > +{ > + int i; > + struct kvm_run *run = vcpu->run; > + > + if (!vcpu->kvm->arch.hvc_to_user) { > + smccc_set_retval(vcpu, SMCCC_RET_NOT_SUPPORTED, 0, 0, 0); > + return 1; > + } > + > + run->exit_reason = KVM_EXIT_HYPERCALL; > + run->hypercall.nr = kvm_vcpu_hvc_get_imm(vcpu); > + /* Copy the first parameters for fast access */ > + for (i = 0; i < 6; i++) > + run->hypercall.args[i] = vcpu_get_reg(vcpu, i); > + run->hypercall.ret = 0; > + run->hypercall.longmode = 0; > + run->hypercall.pad = 0; > + > + return 0; > +} > + > int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) > { > u32 func_id = smccc_get_function(vcpu); > @@ -139,8 +161,12 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) > case ARM_SMCCC_TRNG_RND32: > case ARM_SMCCC_TRNG_RND64: > return kvm_trng_call(vcpu); > - default: > + case KVM_PSCI_FN_BASE...KVM_PSCI_FN_LAST: > + case PSCI_0_2_FN_BASE...PSCI_0_2_FN_LAST: > + case PSCI_0_2_FN64_BASE...PSCI_0_2_FN64_LAST: > return kvm_psci_call(vcpu); > + default: > + return kvm_hvc_user(vcpu); > } > > smccc_set_retval(vcpu, val[0], val[1], val[2], val[3]); _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel