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 914812116F5 for ; Wed, 12 Feb 2025 18:48:44 +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=1739386127; cv=none; b=SMJm3Sa8cnE/KFxTk7HEJqoCL4NHNqtwPsJT1+8XWBQKYzH83Pk1DNoIXsWS6kurkjIdp9HTGNC58onDujL0hYVE+L4ZaBR1y9AuSm1tTaTDkUboxS68yS4rdB3FNfKJMl2U5OBsC0SJpdBxxzzWDFdyqx5o5vvave2myIHivB0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739386127; c=relaxed/simple; bh=EPaDlXqdeo/5WchY7h4bV0WV4vJvAT4/PZlfRf6blgM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XDo+FyAT4sIonmm0I0bvLjiy+8+HsPQBQG1MYOBdhyY3BPs9rZSbRPFHfk4mKESrzl52YDX0MeZjIv2NAG7BY2XvVBEBVt1VAwfWpZEuiHu5oW5wNNw/ioMeq/BZaPI1A2VDexNNye83Swb44Bp/qDqL2jB+DyXbebhRcpJIHP4= 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 D6BFA113E; Wed, 12 Feb 2025 10:49:04 -0800 (PST) Received: from [10.57.36.240] (unknown [10.57.36.240]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 083613F58B; Wed, 12 Feb 2025 10:48:41 -0800 (PST) Message-ID: <55743353-60fb-4ad2-a0c2-6d5a3a2f8ac0@arm.com> Date: Wed, 12 Feb 2025 18:48:40 +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 1/1] arm64: realm: Use aliased addresses for device DMA to shared buffers Content-Language: en-GB To: Robin Murphy , will@kernel.org, maz@kernel.org, catalin.marinas@arm.com Cc: 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: <20250212171411.951874-1-suzuki.poulose@arm.com> <20250212171411.951874-2-suzuki.poulose@arm.com> <7ebe959b-132e-468a-bad5-5273427b6928@arm.com> From: Suzuki K Poulose In-Reply-To: <7ebe959b-132e-468a-bad5-5273427b6928@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Robin On 12/02/2025 18:18, Robin Murphy wrote: > On 2025-02-12 5:14 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. >> >> Add the support for this by providing arm64 version of the >> phys_to_dma(). We >> cannot use the __sme_mask as it assumes the "encryption" always "sets >> a bit", >> which is the opposite for CCA. i.e., "set a bit" for "decrypted" >> address. So, >> move the common code that can be reused by all - i.e., add >> __phys_to_dma() and >> __dma_to_phys() - and do the arch specific processing. >> >> 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 >> Signed-off-by: Suzuki K Poulose >> --- >>   arch/arm64/Kconfig                  |  1 + >>   arch/arm64/include/asm/dma-direct.h | 38 +++++++++++++++++++++++++++++ >>   include/linux/dma-direct.h          | 35 +++++++++++++++++--------- >>   3 files changed, 62 insertions(+), 12 deletions(-) >>   create mode 100644 arch/arm64/include/asm/dma-direct.h >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index fcdd0ed3eca8..7befe04106de 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -41,6 +41,7 @@ config ARM64 >>       select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS >>       select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE >>       select ARCH_HAS_NONLEAF_PMD_YOUNG if ARM64_HAFT >> +    select ARCH_HAS_PHYS_TO_DMA >>       select ARCH_HAS_PTE_DEVMAP >>       select ARCH_HAS_PTE_SPECIAL >>       select ARCH_HAS_HW_PTE_YOUNG >> diff --git a/arch/arm64/include/asm/dma-direct.h b/arch/arm64/include/ >> asm/dma-direct.h >> new file mode 100644 >> index 000000000000..37c3270542b8 >> --- /dev/null >> +++ b/arch/arm64/include/asm/dma-direct.h >> @@ -0,0 +1,38 @@ >> +/* SPDX-License-Identifier: GPL-2.0-only */ >> +#ifndef __ASM_DMA_DIRECT_H >> +#define __ASM_DMA_DIRECT_H >> + >> +#include >> + >> +static inline unsigned long addr_to_shared(unsigned long addr) >> +{ >> +    if (is_realm_world()) >> +        addr |= prot_ns_shared; >> +    return addr; >> +} >> + >> +static inline unsigned long addr_to_private(unsigned long addr) >> +{ >> +    if (is_realm_world()) >> +        addr &= prot_ns_shared - 1; >> +    return addr; >> +} >> + >> +static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t >> paddr) >> +{ >> +    return __phys_to_dma(dev, paddr); >> +} >> + >> +static inline dma_addr_t phys_to_dma_unencrypted(struct device *dev, >> +                         phys_addr_t paddr) >> +{ >> +    return addr_to_shared(__phys_to_dma(dev, paddr)); >> +} >> +#define phys_to_dma_unencrypted phys_to_dma_unencrypted >> + >> +static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t >> dma_addr) >> +{ >> +    return addr_to_private(__dma_to_phys(dev, dma_addr)); >> +} >> + >> +#endif    /* __ASM_DMA_DIRECT_H */ >> diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h >> index d7e30d4f7503..3e9bf6ca640e 100644 >> --- a/include/linux/dma-direct.h >> +++ b/include/linux/dma-direct.h >> @@ -72,18 +72,36 @@ static inline dma_addr_t dma_range_map_max(const >> struct bus_dma_region *map) >>       return ret; >>   } >> +static inline dma_addr_t __phys_to_dma(struct device *dev, >> phys_addr_t paddr) >> +{ >> +    if (dev->dma_range_map) >> +        return translate_phys_to_dma(dev, paddr); >> +    return paddr; >> +} >> + >> +static inline phys_addr_t __dma_to_phys(struct device *dev, >> dma_addr_t dma_addr) >> +{ >> +    phys_addr_t paddr; >> + >> +    if (dev->dma_range_map) >> +        paddr = translate_dma_to_phys(dev, dma_addr); >> +    else >> +        paddr = dma_addr; >> + >> +    return paddr; >> +} >> + >>   #ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA >>   #include >>   #ifndef phys_to_dma_unencrypted >>   #define phys_to_dma_unencrypted        phys_to_dma >>   #endif >>   #else >> + >>   static inline dma_addr_t phys_to_dma_unencrypted(struct device *dev, >>           phys_addr_t paddr) >>   { >> -    if (dev->dma_range_map) >> -        return translate_phys_to_dma(dev, paddr); >> -    return paddr; >> +    return __phys_to_dma(dev, paddr); >>   } >>   /* >> @@ -94,19 +112,12 @@ static inline dma_addr_t >> phys_to_dma_unencrypted(struct device *dev, >>    */ >>   static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t >> paddr) >>   { >> -    return __sme_set(phys_to_dma_unencrypted(dev, paddr)); >> +    return __sme_set(__phys_to_dma(dev, paddr)); > > Hmm, it really feels like we should generalise __sme_{set,clr} at this > level, rather than drag in the entire ARCH_HAS_PHYS_TO_DMA override for > the purposes of setting/clearing an address bit just because the > "generic" mechanism for doing that is unashamedly AMD-specific. I was planning to convert that to use ARCH_HAS_PHYS_TO_DMA ;-) too, in a separate patch, to get rid of this "one approach" works for all hook. > > Maybe something like: > > #define dma_shared(x)  sme_clr(x) > #define dma_private(x) sme_set(x) > > for x86, then go from there? But this looks sensible too, can switch to this approach. Thanks for the feedback. Suzuki > > Thanks, > Robin. > >>   } >>   static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t >> dma_addr) >>   { >> -    phys_addr_t paddr; >> - >> -    if (dev->dma_range_map) >> -        paddr = translate_dma_to_phys(dev, dma_addr); >> -    else >> -        paddr = dma_addr; >> - >> -    return __sme_clr(paddr); >> +    return __sme_clr(__dma_to_phys(dev, dma_addr)); >>   } >>   #endif /* !CONFIG_ARCH_HAS_PHYS_TO_DMA */ >