linux-kernel - Re: [PATCH 2/5] iommu/arm-smmu: add IOMMU_CAP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <71d21ee4-6112-0ec9-9074-b2a00f5c207c@arm.com>
Date:   Wed, 19 Jul 2017 11:59:37 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Anup Patel <anup.patel@...adcom.com>,
        Will Deacon <will.deacon@....com>,
        Joerg Roedel <joro@...tes.org>,
        Baptiste Reynal <b.reynal@...tualopensystems.com>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     Scott Branden <sbranden@...adcom.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, kvm@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH 2/5] iommu/arm-smmu: add IOMMU_CAP_BYPASS to the ARM SMMU
 driver

On 19/07/17 10:33, Anup Patel wrote:
> The ARM SMMUv1 and SMMUv2 support bypassing transactions for
> which domain is not configured. The patch adds corresponding
> IOMMU capability to advertise this fact.
> 
> Signed-off-by: Anup Patel <anup.patel@...adcom.com>
> ---
>  drivers/iommu/arm-smmu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index bc89b4d..08a9020 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1483,6 +1483,8 @@ static bool arm_smmu_capable(enum iommu_cap cap)
>  		return true;
>  	case IOMMU_CAP_NOEXEC:
>  		return true;
> +	case IOMMU_CAP_BYPASS:
> +		return true;

Except when it isn't, of course.

Beware that what we'd like to do in the long term is flip the polarity
of disable_bypass, because there isn't generally a good reason for
Non-Secure DMA to be happening behind Linux's back.

Robin.

>  	default:
>  		return false;
>  	}
>