From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3E42CC282DE for ; Thu, 13 Mar 2025 14:02:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=wYBSTQZkpol7T1dKE62nFL+WbYIAMEdcURh6EKQh7UA=; b=O6rcTZVqRjDLD3EQaVwgGEpvQi 3rKTatWNEay5amXSOdLISskLE05QXLvLXfmefCsbKOohVTikbzxKy6Q1QTmxCFq8thcORVOFFOW4z qH2YwhbnDL1sqjRKyaYkzMsySHcEvnh0Kcpc/L28rWNW0zkvGQOeUtPXfQUmOmtcfjD6gQ6MBm2Zf ZEe5N5qhdFZ4T7I8HiXViGWu9ojJs5Ku0BTWNlp+P6u/2bVOpb6rvYHJijVI8eJMsxQXTagZ9hAlR ANfxLY+aKKML1thCqs6Xrsm+OkA9IqN0VcmFzC+RNhfHcF71d6IoB0C5UIwnC7mu7Pyh7CVmF+pe0 jHx8wv7Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tsj8U-0000000BTkq-28h5; Thu, 13 Mar 2025 14:02:10 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tsj6q-0000000BTZJ-2DPh for linux-arm-kernel@lists.infradead.org; Thu, 13 Mar 2025 14:00:29 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C62F91424; Thu, 13 Mar 2025 07:00:37 -0700 (PDT) Received: from bogus (e133711.arm.com [10.1.196.55]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CD2283F694; Thu, 13 Mar 2025 07:00:24 -0700 (PDT) Date: Thu, 13 Mar 2025 14:00:21 +0000 From: Sudeep Holla To: Will Deacon Cc: Sebastian Ene , catalin.marinas@arm.com, Sudeep Holla , joey.gouly@arm.com, maz@kernel.org, oliver.upton@linux.dev, snehalreddy@google.com, suzuki.poulose@arm.com, vdonnefort@google.com, yuzenghui@huawei.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-team@android.com, Andrei Homescu Subject: Re: [PATCH v2 4/4] KVM: arm64: Release the ownership of the hyp rx buffer to Trustzone Message-ID: References: <20250227181750.3606372-1-sebastianene@google.com> <20250227181750.3606372-5-sebastianene@google.com> <20250305004522.GC31667@willie-the-truck> <20250305094104.vctshdtgdukno2aj@bogus> <20250305193425.GA32246@willie-the-truck> <20250313121559.GB7356@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250313121559.GB7356@willie-the-truck> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250313_070028_651180_65B75DBC X-CRM114-Status: GOOD ( 28.41 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Mar 13, 2025 at 12:15:59PM +0000, Will Deacon wrote: > On Thu, Mar 06, 2025 at 09:40:43AM +0000, Sudeep Holla wrote: > > On Wed, Mar 05, 2025 at 07:34:26PM +0000, Will Deacon wrote: > > > On Wed, Mar 05, 2025 at 09:41:04AM +0000, Sudeep Holla wrote: > > > > On Wed, Mar 05, 2025 at 12:45:23AM +0000, Will Deacon wrote: > > > > > Hmm, the FFA spec is characteristically unclear as to whether or not we > > > > > need to release the rx buffer in the case that the flags indicate use of > > > > > the rx buffer but the returned partition count is 0. > > > > > > > > > > Sudeep -- do you know what we should be doing in that case? > > > > > > > > > > > > > We need to call RX_RELEASE here. I went back to the spec to confirm the > > > > same again. > > > > > > > > v1.2 EAC0 spec Section 7.2.2.4.2 Transfer of buffer ownership > > > > (Or just look for the section title in any version of the spec) > > > > " > > > > 2. Ownership transfer for the RX buffer takes place as follows. > > > > 2. For a framework message, > > > > 1. Completion of the FFA_PARTITION_INFO_GET ABI transfers the ownership > > > > of the caller’s RX buffer from the Producer to the Consumer. > > > > 3. For both types of messages, an invocation of the following FF-A ABIs > > > > transfers the ownership from the Consumer to the Producer. > > > > 1. FFA_MSG_WAIT ... > > > > 2. FFA_RX_RELEASE. > > > > " > > > > > > > > Hope that helps, can dig deeper if there are any ambiguities around this. > > > > > > Thanks Sudeep, but that also makes it sound like we need the RX_RELEASE > > > even if we're not using the RX buffer per the input flags. :/ > > > > > > > Good spot, I had forgotten about the input flags that can avoid using the > > buffer. I will see if we can improve the spec in that regards. > > Thanks. In the meantime, what do you think is the correct behaviour in that > case? I guess _not_ doing the release when the flags don't request the RX > buffer? In other words: > > > if (flags & PARTITION_INFO_GET_RETURN_COUNT_ONLY) > goto out_unlock; > > if (!count) > goto release_rx; > > [...] > > if (copy_sz > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) { > ffa_to_smccc_res(res, FFA_RET_ABORTED); > goto release_rx; > } > > memcpy(host_buffers.rx, hyp_buffers.rx, copy_sz); > release_rx: > ffa_rx_release(&_res); > out_unlock: > hyp_spin_unlock(&host_buffers.lock); > } > > > What do you reckon? Yes matches my understanding. I also cross checked with FF-A spec authors to be sure. Now I got to fix that in the driver, currently it releases buffer unconditionally which is wrong 🙁. -- Regards, Sudeep