From nobody Sun Feb 8 11:37:52 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 F1B56C61D9C for ; Wed, 22 Nov 2023 12:30:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344103AbjKVMad (ORCPT ); Wed, 22 Nov 2023 07:30:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35670 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343584AbjKVMaa (ORCPT ); Wed, 22 Nov 2023 07:30:30 -0500 Received: from mail.xenproject.org (mail.xenproject.org [104.130.215.37]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B174D92; Wed, 22 Nov 2023 04:30:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:MIME-Version:References: In-Reply-To:Message-Id:Date:Subject:To:From; bh=CPp0Qc6lsksup1D7/LciCKmODvP2NLwil1ZR7D0Jz3s=; b=CQhJKbRt3pgU5rBJ+Vvi7X+I7D BhzUIaYVj/Dxf1Nj109ocJ0OWdOTWRTOsQJipQil38bfXXkD1IuL8wEzM5KlLjsZU+tj2yqgK9dfZ iU8GayAtIMOpi5M1HdWOnf48fZn9UHxekRKhPFPsWuId7rrvAIawOB3XTO5Ichu1nzuQ=; Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1r5mN0-0005E6-2b; Wed, 22 Nov 2023 12:30:18 +0000 Received: from 54-240-197-231.amazon.com ([54.240.197.231] helo=REM-PW02S00X.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1r5mCp-0004y9-EI; Wed, 22 Nov 2023 12:19:47 +0000 From: Paul Durrant To: David Woodhouse , Paul Durrant , Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v9 15/15] KVM: xen: allow vcpu_info content to be 'safely' copied Date: Wed, 22 Nov 2023 12:18:22 +0000 Message-Id: <20231122121822.1042-16-paul@xen.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231122121822.1042-1-paul@xen.org> References: <20231122121822.1042-1-paul@xen.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Paul Durrant If the guest sets an explicit vcpu_info GPA then, for any of the first 32 vCPUs, the content of the default vcpu_info in the shared_info page must be copied into the new location. Because this copy may race with event delivery (which updates the 'evtchn_pending_sel' field in vcpu_info) there needs to be a way to defer that until the copy is complete. Happily there is already a shadow of 'evtchn_pending_sel' in kvm_vcpu_xen that is used in atomic context if the vcpu_info PFN cache has been invalidated so that the update of vcpu_info can be deferred until the cache can be refreshed (on vCPU thread's the way back into guest context). Also use this shadow if the vcpu_info cache has been *deactivated*, so that the VMM can safely copy the vcpu_info content and then re-activate the cache with the new GPA. To do this, stop considering an inactive vcpu_info cache as a hard error in kvm_xen_set_evtchn_fast(). Signed-off-by: Paul Durrant Reviewed-by: David Woodhouse --- Cc: David Woodhouse Cc: Sean Christopherson Cc: Paolo Bonzini Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: x86@kernel.org v8: - Update commit comment. v6: - New in this version. --- arch/x86/kvm/xen.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index eff405eead1c..cfd5051e0800 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -1742,9 +1742,6 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe= , struct kvm *kvm) WRITE_ONCE(xe->vcpu_idx, vcpu->vcpu_idx); } =20 - if (!vcpu->arch.xen.vcpu_info_cache.active) - return -EINVAL; - if (xe->port >=3D max_evtchn_port(kvm)) return -EINVAL; =20 --=20 2.39.2