From nobody Wed Apr 8 17:33:29 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 13D0BFA3740 for ; Thu, 27 Oct 2022 16:19:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236721AbiJ0QTr (ORCPT ); Thu, 27 Oct 2022 12:19:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236563AbiJ0QTA (ORCPT ); Thu, 27 Oct 2022 12:19:00 -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 10369196B5E for ; Thu, 27 Oct 2022 09:18:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666887536; 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=C6aHPqfRabBG7+Uh3PTVNYMLpzQUUZusTV/Bql6znhc=; b=Kbe1I/sNO75wMA2loxlsaDMI/D12wUSv/n6iAQNX6C9Ke+oWNACYf1BTZRpAiPCqBf2wmV 8NSYz9ETe65ISbdBllse8QKZNFlzUCwv1FVzX27aURWXfno6OAJ1yZSct0tNdPfydJMLXe bq+AUBg0WaGw9UygW8J/VzzXHlGpXVY= 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-558-lUjuoMU0PFaeMn5n0Jqg-A-1; Thu, 27 Oct 2022 12:18:52 -0400 X-MC-Unique: lUjuoMU0PFaeMn5n0Jqg-A-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6605E3C025CA; Thu, 27 Oct 2022 16:18:52 +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 44CC717593; Thu, 27 Oct 2022 16:18:52 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: mhal@rbox.co, seanjc@google.com Subject: [PATCH 11/16] KVM: Drop KVM's API to allow temprorarily unmapping gfn=>pfn cache Date: Thu, 27 Oct 2022 12:18:44 -0400 Message-Id: <20221027161849.2989332-12-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 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Sean Christopherson Drop kvm_gpc_unmap() as it has no users and unclear requirements. The API was added as part of the original gfn_to_pfn_cache support, but its sole usage[*] was never merged. Fold the guts of kvm_gpc_unmap() into the deactivate path and drop the API. Omit acquiring refresh_lock as as concurrent calls to kvm_gpc_deactivate() are not allowed (this is not enforced, e.g. via lockdep. due to it being called during vCPU destruction). If/when temporary unmapping makes a comeback, the desirable behavior is likely to restrict temporary unmapping to vCPU-exclusive mappings and require the vcpu->mutex be held to serialize unmap. Use of the refresh_lock to protect unmapping was somewhat specuatively added by commit 93984f19e7bc ("KVM: Fully serialize gfn=3D>pfn cache refresh via mutex") to guard against concurrent unmaps, but the primary use case of the temporary unmap, nested virtualization[*], doesn't actually need or want concurrent unmaps. [*] https://lore.kernel.org/all/20211210163625.2886-7-dwmw2@infradead.org Signed-off-by: Sean Christopherson Message-Id: <20221013211234.1318131-12-seanjc@google.com> Signed-off-by: Paolo Bonzini --- include/linux/kvm_host.h | 12 ----------- virt/kvm/pfncache.c | 44 +++++++++++++++------------------------- 2 files changed, 16 insertions(+), 40 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d4a49c89bc08..3847b721e753 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1314,18 +1314,6 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa= _t gpa); */ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa); =20 -/** - * kvm_gpc_unmap - temporarily unmap a gfn_to_pfn_cache. - * - * @kvm: pointer to kvm instance. - * @gpc: struct gfn_to_pfn_cache object. - * - * This unmaps the referenced page. The cache is left in the invalid state - * but at least the mapping from GPA to userspace HVA will remain cached - * and can be reused on a subsequent refresh. - */ -void kvm_gpc_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc); - /** * kvm_gpc_deactivate - deactivate and unlink a gfn_to_pfn_cache. * diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index e4ebea75dca9..62429b2a6389 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -335,33 +335,6 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_= t gpa) } EXPORT_SYMBOL_GPL(kvm_gpc_refresh); =20 -void kvm_gpc_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc) -{ - void *old_khva; - kvm_pfn_t old_pfn; - - mutex_lock(&gpc->refresh_lock); - write_lock_irq(&gpc->lock); - - gpc->valid =3D false; - - old_khva =3D gpc->khva - offset_in_page(gpc->khva); - old_pfn =3D gpc->pfn; - - /* - * We can leave the GPA \ufffd\ufffd\ufffd uHVA map cache intact but the = PFN - * lookup will need to be redone even for the same page. - */ - gpc->khva =3D NULL; - gpc->pfn =3D KVM_PFN_ERR_FAULT; - - write_unlock_irq(&gpc->lock); - mutex_unlock(&gpc->refresh_lock); - - gpc_unmap_khva(old_pfn, old_khva); -} -EXPORT_SYMBOL_GPL(kvm_gpc_unmap); - void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm, struct kvm_vcpu *vcpu, enum pfn_cache_usage usage) { @@ -407,6 +380,8 @@ EXPORT_SYMBOL_GPL(kvm_gpc_activate); void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc) { struct kvm *kvm =3D gpc->kvm; + kvm_pfn_t old_pfn; + void *old_khva; =20 if (gpc->active) { /* @@ -416,13 +391,26 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc) */ write_lock_irq(&gpc->lock); gpc->active =3D false; + gpc->valid =3D false; + + /* + * Leave the GPA =3D> uHVA cache intact, it's protected by the + * memslot generation. The PFN lookup however will have to be + * redone after the cache is removed from the VM's gpc_list, + * as that loses mmu_notifier protection. + */ + old_khva =3D gpc->khva - offset_in_page(gpc->khva); + gpc->khva =3D NULL; + + old_pfn =3D gpc->pfn; + gpc->pfn =3D KVM_PFN_ERR_FAULT; write_unlock_irq(&gpc->lock); =20 spin_lock(&kvm->gpc_lock); list_del(&gpc->list); spin_unlock(&kvm->gpc_lock); =20 - kvm_gpc_unmap(kvm, gpc); + gpc_unmap_khva(old_pfn, old_khva); } } EXPORT_SYMBOL_GPL(kvm_gpc_deactivate); --=20 2.31.1