From nobody Wed Apr 8 17:28:29 2026 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 12186FA3740 for ; Thu, 27 Oct 2022 16:19:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236649AbiJ0QTS (ORCPT ); Thu, 27 Oct 2022 12:19:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236515AbiJ0QSz (ORCPT ); Thu, 27 Oct 2022 12:18:55 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E12281958CE for ; Thu, 27 Oct 2022 09:18:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666887533; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QUVijSFivcu94lUnkyEd2RGaEvfXWEp1CBYc7P4eIz8=; b=a/qs2mRyQQtQ1ANBA0qqgl0FQdgOVvrgGaTTTCpuU+1yMTdodQRVhOmKvhsuyvm9CzZfnH hQMrbxjn/FZlyGBUC4W/50b7ep2os+51bpL90NZ6i/pe658THEBqXNSxIi1wCyL+i0fQFi UulhIqkndc6G10S5kCG7KWXLYsZF17k= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-550-mg8LLvftPvWJXbuX6Lw-5Q-1; Thu, 27 Oct 2022 12:18:51 -0400 X-MC-Unique: mg8LLvftPvWJXbuX6Lw-5Q-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CFC311C0896E; Thu, 27 Oct 2022 16:18:50 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id AD54E1415117; Thu, 27 Oct 2022 16:18:50 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: mhal@rbox.co, seanjc@google.com Subject: [PATCH 03/16] KVM: x86: set gfn-to-pfn cache length consistently with VM word size Date: Thu, 27 Oct 2022 12:18:36 -0400 Message-Id: <20221027161849.2989332-4-pbonzini@redhat.com> In-Reply-To: <20221027161849.2989332-1-pbonzini@redhat.com> References: <20221027161849.2989332-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" KVM unconditionally uses the "full" size of the Xen shared info page when activating the cache in kvm_xen_vcpu_set_attr(), but using the current mode matches what Xen does. While KVM did always use the 64-bit size when activating the cache, what matters is that Xen does not look beyond the size of the 32-bit struct if the vCPU was initialized in 32-bit mode. If the guest sets up the runstate info of a 32-bit VM so that the struct ends at the end of a page, the 64-bit struct size passed to kvm_gpc_activate() will cause the ioctl or hypercall to fail, because gfn-to-pfn caches can only be set up for data that fits in a single page. Nevertheless, keeping the Xen word size constant throughout the life of the gpc cache, i.e. not using a different size at check()+refresh() than at activate(), is desirable because it makes the length/size of the cache immutable. This in turn yields a cleaner set of APIs and avoids potential bugs that could occur if check() were invoked with a different size than refresh(). So, use the short size at activation time as well. This means re-activating the cache if the guest requests the hypercall page multiple times with different word sizes (this can happen when kexec-ing, for example). Signed-off-by: Paolo Bonzini --- arch/x86/kvm/xen.c | 47 +++++++++++++++++++++++++++++++++++++--------- 1 file changed, 38 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index b2be60c6efa4..512b4afa6785 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -198,6 +198,37 @@ static void kvm_xen_update_runstate(struct kvm_vcpu *v= , int state) vx->runstate_entry_time =3D now; } =20 +static inline size_t kvm_xen_runstate_info_size(struct kvm *kvm) +{ + if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) + return sizeof(struct vcpu_runstate_info); + else + return sizeof(struct compat_vcpu_runstate_info); +} + +static int kvm_xen_activate_runstate_gpc(struct kvm_vcpu *vcpu, unsigned l= ong gpa) +{ + size_t user_len =3D kvm_xen_runstate_info_size(vcpu->kvm); + return kvm_gpc_activate(vcpu->kvm, &vcpu->arch.xen.runstate_cache, + NULL, KVM_HOST_USES_PFN, gpa, user_len); +} + +static int kvm_xen_reactivate_runstate_gpcs(struct kvm *kvm) +{ + struct kvm_vcpu *vcpu; + unsigned long i; + + kvm_for_each_vcpu(i, vcpu, kvm) { + if (vcpu->arch.xen.runstate_cache.active) { + int r =3D kvm_xen_activate_runstate_gpc(vcpu, + vcpu->arch.xen.runstate_cache.gpa); + if (r < 0) + return r; + } + } + return 0; +} + void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, int state) { struct kvm_vcpu_xen *vx =3D &v->arch.xen; @@ -212,11 +243,7 @@ void kvm_xen_update_runstate_guest(struct kvm_vcpu *v,= int state) if (!vx->runstate_cache.active) return; =20 - if (IS_ENABLED(CONFIG_64BIT) && v->kvm->arch.xen.long_mode) - user_len =3D sizeof(struct vcpu_runstate_info); - else - user_len =3D sizeof(struct compat_vcpu_runstate_info); - + user_len =3D kvm_xen_runstate_info_size(v->kvm); read_lock_irqsave(&gpc->lock, flags); while (!kvm_gfn_to_pfn_cache_check(v->kvm, gpc, gpc->gpa, user_len)) { @@ -461,7 +488,7 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xe= n_hvm_attr *data) mutex_lock(&kvm->lock); kvm->arch.xen.long_mode =3D !!data->u.long_mode; mutex_unlock(&kvm->lock); - r =3D 0; + r =3D kvm_xen_reactivate_runstate_gpcs(kvm); } break; =20 @@ -596,9 +623,7 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct= kvm_xen_vcpu_attr *data) break; } =20 - r =3D kvm_gpc_activate(vcpu->kvm, &vcpu->arch.xen.runstate_cache, - NULL, KVM_HOST_USES_PFN, data->u.gpa, - sizeof(struct vcpu_runstate_info)); + r =3D kvm_xen_activate_runstate_gpc(vcpu, data->u.gpa); break; =20 case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT: @@ -843,9 +868,13 @@ int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu= , u64 data) u32 page_num =3D data & ~PAGE_MASK; u64 page_addr =3D data & PAGE_MASK; bool lm =3D is_long_mode(vcpu); + int r; =20 /* Latch long_mode for shared_info pages etc. */ vcpu->kvm->arch.xen.long_mode =3D lm; + r =3D kvm_xen_reactivate_runstate_gpcs(kvm); + if (r < 0) + return 1; =20 /* * If Xen hypercall intercept is enabled, fill the hypercall --=20 2.31.1