From patchwork Sat Nov 20 10:28:08 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 12630277 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E26EC31D68 for ; Sat, 20 Nov 2021 10:28:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237336AbhKTKbt (ORCPT ); Sat, 20 Nov 2021 05:31:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43146 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230365AbhKTKbk (ORCPT ); Sat, 20 Nov 2021 05:31:40 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07136C06175A; Sat, 20 Nov 2021 02:28:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description; bh=CfsPll4/NdPuO0toqkRUmnZ03yoAM6IomYyn/Hv8YUw=; b=lDvGLdHU6s89Lp+FfbSx8JRQr7 S9cELf+pj/hpLk7u43/rBSdPpxRy1oaE4Rc1eJ8cgCT7F5EHNfgpmUyLv2g7Kr0EGIYzDA6LeQ4IW uqtDt4/f697C488QG4DY2ugmRqwio+nP5mAVhMQdIubEyqlUV4hMoj7tG9+kJlqF+VrU2qv/3mduz 7sbvFWiKj3Cuw0PLq77tSSgYJ3bANDX6eVixBewnt9obd1NMyfdWvOA9LrUwLVh7CGlbyMvr1mWLg SY9rkM2ZwA/IpjU9TfKeXxcmX1muhggaZvgrLYJx85mFMNaVzOze+zrcihfNabiX94qzu4ci+lszN tTsOBqJw==; Received: from i7.infradead.org ([2001:8b0:10b:1:21e:67ff:fecb:7a92]) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1moNbR-00H55t-Hr; Sat, 20 Nov 2021 10:28:13 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1moNbQ-0002KT-TJ; Sat, 20 Nov 2021 10:28:12 +0000 From: David Woodhouse To: Paolo Bonzini , kvm Cc: Boris Ostrovsky , Joao Martins , "jmattson @ google . com" , "wanpengli @ tencent . com" , "seanjc @ google . com" , "vkuznets @ redhat . com" , "mtosatti @ redhat . com" , "joro @ 8bytes . org" , karahmed@amazon.com, Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Catalin Marinas , Will Deacon , Huacai Chen , Aleksandar Markovic , Michael Ellerman , Benjamin Herrenschmidt , Anup Patel , Christian Borntraeger , kvmarm@lists.cs.columbia.edu, linux-arm-kernel , linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-s390@vger.kernel.org Subject: [PATCH v4 09/11] KVM: x86/xen: Maintain valid mapping of Xen shared_info page Date: Sat, 20 Nov 2021 10:28:08 +0000 Message-Id: <20211120102810.8858-10-dwmw2@infradead.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20211120102810.8858-1-dwmw2@infradead.org> References: <20211120102810.8858-1-dwmw2@infradead.org> MIME-Version: 1.0 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse Use the newly reinstated gfn_to_pfn_cache to maintain a kernel mapping of the Xen shared_info page so that it can be accessed in atomic context. Note that we do not participate in dirty tracking for the shared info page and we do not explicitly mark it dirty every single tim we deliver an event channel interrupts. We wouldn't want to do that even if we *did* have a valid vCPU context with which to do so. Signed-off-by: David Woodhouse --- Documentation/virt/kvm/api.rst | 12 ++++++++++++ arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/xen.c | 25 ++++++++++++++----------- 3 files changed, 27 insertions(+), 12 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index aeeb071c7688..455664c39d42 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -371,6 +371,9 @@ The bits in the dirty bitmap are cleared before the ioctl returns, unless KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is enabled. For more information, see the description of the capability. +Note that the Xen shared info page, if configured, shall always be assumed +to be dirty. KVM will not explicitly mark it such. + 4.9 KVM_SET_MEMORY_ALIAS ------------------------ @@ -5134,6 +5137,15 @@ KVM_XEN_ATTR_TYPE_SHARED_INFO not aware of the Xen CPU id which is used as the index into the vcpu_info[] array, so cannot know the correct default location. + Note that the shared info page may be constantly written to by KVM; + it contains the event channel bitmap used to deliver interrupts to + a Xen guest, amongst other things. It is exempt from dirty tracking + mechanisms — KVM will not explicitly mark the page as dirty each + time an event channel interrupt is delivered to the guest! Thus, + userspace should always assume that the designated GFN is dirty if + any vCPU has been running or any event channel interrupts can be + routed to the guest. + KVM_XEN_ATTR_TYPE_UPCALL_VECTOR Sets the exception vector used to deliver Xen event channel upcalls. diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 6ac61f85e07b..4b2b4ecf3b46 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1014,7 +1014,7 @@ struct msr_bitmap_range { struct kvm_xen { bool long_mode; u8 upcall_vector; - gfn_t shinfo_gfn; + struct gfn_to_pfn_cache shinfo_cache; }; enum kvm_irqchip_mode { diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index dff2bdf9507a..da4bf2c6407f 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -23,16 +23,21 @@ DEFINE_STATIC_KEY_DEFERRED_FALSE(kvm_xen_enabled, HZ); static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn) { + struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache; gpa_t gpa = gfn_to_gpa(gfn); int wc_ofs, sec_hi_ofs; int ret = 0; int idx = srcu_read_lock(&kvm->srcu); - if (kvm_is_error_hva(gfn_to_hva(kvm, gfn))) { - ret = -EFAULT; + if (gfn == GPA_INVALID) { + kvm_gfn_to_pfn_cache_destroy(kvm, gpc); goto out; } - kvm->arch.xen.shinfo_gfn = gfn; + + ret = kvm_gfn_to_pfn_cache_init(kvm, gpc, NULL, false, true, gpa, + PAGE_SIZE, false); + if (ret) + goto out; /* Paranoia checks on the 32-bit struct layout */ BUILD_BUG_ON(offsetof(struct compat_shared_info, wc) != 0x900); @@ -260,15 +265,9 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) break; case KVM_XEN_ATTR_TYPE_SHARED_INFO: - if (data->u.shared_info.gfn == GPA_INVALID) { - kvm->arch.xen.shinfo_gfn = GPA_INVALID; - r = 0; - break; - } r = kvm_xen_shared_info_init(kvm, data->u.shared_info.gfn); break; - case KVM_XEN_ATTR_TYPE_UPCALL_VECTOR: if (data->u.vector && data->u.vector < 0x10) r = -EINVAL; @@ -299,7 +298,10 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) break; case KVM_XEN_ATTR_TYPE_SHARED_INFO: - data->u.shared_info.gfn = kvm->arch.xen.shinfo_gfn; + if (kvm->arch.xen.shinfo_cache.active) + data->u.shared_info.gfn = gpa_to_gfn(kvm->arch.xen.shinfo_cache.gpa); + else + data->u.shared_info.gfn = GPA_INVALID; r = 0; break; @@ -661,11 +663,12 @@ int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc) void kvm_xen_init_vm(struct kvm *kvm) { - kvm->arch.xen.shinfo_gfn = GPA_INVALID; } void kvm_xen_destroy_vm(struct kvm *kvm) { + kvm_gfn_to_pfn_cache_destroy(kvm, &kvm->arch.xen.shinfo_cache); + if (kvm->arch.xen_hvm_config.msr) static_branch_slow_dec_deferred(&kvm_xen_enabled); }