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 61792C021B2 for ; Tue, 25 Feb 2025 13:31:23 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=qYdR8VXU4L5+CSAij77UvNBiqWRdJxMRzbGNmmZDrwc=; b=0O8X7J577tYNKM9Uv0SDo8cuEK B/AjOagzMWLWVZBkgTAVS/E0aWB9hEyhdrL3Vxt12Jv4nOrD+8EZygThEMV+wsqV6/tcyzy1nCPeh Ug2tUpLOUc/cm4cn1MoyHhJanWIXY0ylnPibxraTPhP1Q9dX2AqhkD88Zs4kMvQT4zdsrFS0+DnDd +G+G73NVI+qrkSZZ4qUvEDrWhKQg3oEM8w9gPOQSH2kq3EqD7dWRnFXfhtNs4EGFvgc57kJpzNnvl 4r12eYc4Sm7rFSSX0oWU/EJOdDscLQ/hULbUPOqQjuV3+eCU0RM0Z+v26xy7s3wgJF5KuPDrtcNii MlINnxdw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tmv1k-0000000HNrY-167U; Tue, 25 Feb 2025 13:31:12 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tmuc3-0000000HIaL-1zbG for linux-arm-kernel@lists.infradead.org; Tue, 25 Feb 2025 13:04:40 +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 57456152B; Tue, 25 Feb 2025 05:04:55 -0800 (PST) Received: from [10.57.38.173] (unknown [10.57.38.173]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5956E3F5A1; Tue, 25 Feb 2025 05:04:37 -0800 (PST) Message-ID: <0b0705aa-8c85-4502-8450-a6c7fdbdbdbd@arm.com> Date: Tue, 25 Feb 2025 13:04:35 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/3] arm64: realm: Use aliased addresses for device DMA to shared buffers To: Suzuki K Poulose , will@kernel.org, catalin.marinas@arm.com Cc: maz@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, aneesh.kumar@kernel.org, steven.price@arm.com, Jean-Philippe Brucker , Christoph Hellwig , Tom Lendacky References: <20250219220751.1276854-1-suzuki.poulose@arm.com> <20250219220751.1276854-4-suzuki.poulose@arm.com> From: Robin Murphy Content-Language: en-GB In-Reply-To: <20250219220751.1276854-4-suzuki.poulose@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250225_050439_568983_B8062659 X-CRM114-Status: GOOD ( 20.44 ) 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 2025-02-19 10:07 pm, Suzuki K Poulose wrote: > When a device performs DMA to a shared buffer using physical addresses, > (without Stage1 translation), the device must use the "{I}PA address" with the > top bit set in Realm. This is to make sure that a trusted device will be able > to write to shared buffers as well as the protected buffers. Thus, a Realm must > always program the full address including the "protection" bit, like AMD SME > encryption bits. > > Enable this by providing arm64 specific dma_{encrypted,decrypted,clear_encryption} > helpers for Realms. Please note that the VMM needs to similarly make sure that > the SMMU Stage2 in the Non-secure world is setup accordingly to map IPA at the > unprotected alias. > > Cc: Will Deacon > Cc: Jean-Philippe Brucker > Cc: Catalin Marinas > Cc: Robin Murphy > Cc: Steven Price > Cc: Christoph Hellwig > Cc: Tom Lendacky > Cc: Aneesh Kumar K.V > Signed-off-by: Suzuki K Poulose > --- > arch/arm64/include/asm/mem_encrypt.h | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/arch/arm64/include/asm/mem_encrypt.h b/arch/arm64/include/asm/mem_encrypt.h > index f8f78f622dd2..aeda3bba255e 100644 > --- a/arch/arm64/include/asm/mem_encrypt.h > +++ b/arch/arm64/include/asm/mem_encrypt.h > @@ -21,4 +21,26 @@ static inline bool force_dma_unencrypted(struct device *dev) > return is_realm_world(); > } > > +static inline dma_addr_t dma_decrypted(dma_addr_t daddr) > +{ > + if (is_realm_world()) > + daddr |= prot_ns_shared; > + return daddr; > +} > +#define dma_decrypted dma_decrypted > + > +static inline dma_addr_t dma_encrypted(dma_addr_t daddr) > +{ > + if (is_realm_world()) > + daddr &= prot_ns_shared - 1; Nit: is there a reason this isn't the direct inverse of the other operation, i.e. "daddr &= ~prot_ns_shared"? If so, it might be worth dropping a comment why we're doing slightly unintuitive arithmetic on a pagetable attribute (and if not then maybe just do the more obvious thing). I doubt anyone's in a rush to support TBI for DMA, and this would be far from the only potential hiccup for that, but still... :) Thanks, Robin. > + return daddr; > +} > +#define dma_encrypted dma_encrypted > + > +static inline dma_addr_t dma_clear_encryption(dma_addr_t daddr) > +{ > + return dma_encrypted(daddr); > +} > +#define dma_clear_encryption dma_clear_encryption > + > #endif /* __ASM_MEM_ENCRYPT_H */