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 BDD422690E7 for ; Tue, 25 Feb 2025 13:04:39 +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=1740488681; cv=none; b=NTOefvsijcWKMnBCvDyj+3HggiPco/d9ZHHCAe+fYsX+VTNlKCxrvTK5dfOBdH0PnQof/YIA9Blm4MfY7+kug1L/+tRkvpw6hXbCMynkw+xhPUM07jlIr8En6YjDkdsc19QITKdQ5VWEKtZbkk2oWG1mm3HhbgEtPixJNDCzdyk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740488681; c=relaxed/simple; bh=V+8Vqwur73cVfgt1CkaSJTemf1XS4pc+2r/TQKRNQao=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lgc7hMbEhHir5ir6VVgg81rkwrcxgDE07vbBzPR+atV3Ki1wgToVLS9tYdjb2aDb71PEc3dC5aDzo4HDdjQk0NECNd7ITq+WZOUDS9pviZcSSC95TLGDi0MX8x4jCBTnKVQ/ieGWAInJyPW+nOIvnTKRIQ8i+w7oLeAFxGFllbY= 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 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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 */