linux-kernel - Re: [PATCH 3/5] iommu/sun50i: Ensure bypass is disabled

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: <1922960.8hb0ThOEGa@jernej-laptop>
Date:   Thu, 28 Apr 2022 07:43:25 +0200
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org,
        Samuel Holland <samuel@...lland.org>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org,
        Samuel Holland <samuel@...lland.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Maxime Ripard <mripard@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH 3/5] iommu/sun50i: Ensure bypass is disabled

Dne četrtek, 28. april 2022 ob 03:03:58 CEST je Samuel Holland napisal(a):
> The H6 variant of the hardware disables bypass by default. The D1
> variant of the hardware enables bypass for all masters by default.
> 
> Since the driver expects bypass to be disabled, ensure that is the case.
> 
> Signed-off-by: Samuel Holland <samuel@...lland.org>

Actually, it would be better to set bypass to 0xff and in 
sun50i_iommu_attach_device() clear bypass bit for that particular device. As 
you might notice, index in phandle is currently not used. This would also help 
expose bugs, like missing second iommu channel for Cedrus on H6, but that's 
easy to fix.

Best regards,
Jernej

> ---
> 
>  drivers/iommu/sun50i-iommu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
> index ec07b60016d3..b9e644b93637 100644
> --- a/drivers/iommu/sun50i-iommu.c
> +++ b/drivers/iommu/sun50i-iommu.c
> @@ -374,6 +374,8 @@ static int sun50i_iommu_enable(struct sun50i_iommu
> *iommu)
> 
>  	spin_lock_irqsave(&iommu->iommu_lock, flags);
> 
> +	iommu_write(iommu, IOMMU_BYPASS_REG, 0);
> +
>  	iommu_write(iommu, IOMMU_TTB_REG, sun50i_domain->dt_dma);
>  	iommu_write(iommu, IOMMU_TLB_PREFETCH_REG,
>  		    IOMMU_TLB_PREFETCH_MASTER_ENABLE(0) |