From patchwork Mon Dec 4 14:43:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Durrant X-Patchwork-Id: 750269 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=xen.org header.i=@xen.org header.b="BXioIzqW" Received: from mail.xenproject.org (mail.xenproject.org [104.130.215.37]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20681C4; Mon, 4 Dec 2023 07:00:31 -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=u3xu4cWioGlm/0Nl4ZRtWZZdIjjd8j62hC7w6zJEnu8=; b=BXioIzqWWZVqflIdLOZVfL3wsh kUWD6QQHc6NI05ep0LckFWjzn50oMDsM0rj1Cv+iUKUaiDciMxW3HG8uWvw0/rWat1sZAdhO3CRp7 Qq7EnjH2a0dNuTdOK6TgXjAicPHkmPHSXn2aLTflELtDsOdkhikEWe/y+JoJ1fCvRPyk=; Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rAAQk-00043d-N8; Mon, 04 Dec 2023 15:00:18 +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 1rAABc-00088g-03; Mon, 04 Dec 2023 14:44:40 +0000 From: Paul Durrant To: Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , David Woodhouse , Paul Durrant , Shuah Khan , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v10 19/19] KVM: xen: allow vcpu_info content to be 'safely' copied Date: Mon, 4 Dec 2023 14:43:34 +0000 Message-Id: <20231204144334.910-20-paul@xen.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231204144334.910-1-paul@xen.org> References: <20231204144334.910-1-paul@xen.org> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 7109d20a4608..72a19956d052 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -1790,9 +1790,6 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm) WRITE_ONCE(xe->vcpu_idx, vcpu->vcpu_idx); } - if (!vcpu->arch.xen.vcpu_info_cache.active) - return -EINVAL; - if (xe->port >= max_evtchn_port(kvm)) return -EINVAL;