From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0A13D2080C5 for ; Thu, 6 Mar 2025 09:40:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741254051; cv=none; b=tn7mLLZvVi3UOS68iM12prWiLuKaTEtNgfHhQn3YQnyByOuymOIow2AfN5QCS/P45esMFw5eHzBebUMQuCjIY5KP0B10Cu44u55DoGRWg/Gv5RkAge/EWsabJJbAICthr+CScFrUA6vxxxxmmQDYV3JBGwgzorGhcaDBiNC5MMI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741254051; c=relaxed/simple; bh=lHzQ/pK6Ei8uZQYcKUxRemCcZhkOdbNoDAUoz5W3/GI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VqHze4uso23HHcsjt2Hah81dHbIokWh6tNFBhwKjAFJL7xRn29vWEGmbFVbUXlVczRwpSTZO3pNryCI43dQJ3b01YpOOYHMm20Ys9n7El9w+ygQCy6uVrexNx+/NWqDIzSb6VOaXC8aWuHNuU+zg6B9NPiVERMMyiS1F9bUBZNU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 44C30FEC; Thu, 6 Mar 2025 01:41:02 -0800 (PST) Received: from bogus (e133711.arm.com [10.1.196.55]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9CA433F673; Thu, 6 Mar 2025 01:40:46 -0800 (PST) Date: Thu, 6 Mar 2025 09:40:43 +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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250305193425.GA32246@willie-the-truck> 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. -- Regards, Sudeep