linux-kernel - Re: [PATCH v4 3/3] iommu: dart: Add DART iommu driver

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: <YNx2U4GPoKxV3PWd@maud>
Date:   Wed, 30 Jun 2021 09:49:07 -0400
From:   Alyssa Rosenzweig <alyssa@...labora.com>
To:     Sven Peter <sven@...npeter.dev>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Arnd Bergmann <arnd@...nel.org>, devicetree@...r.kernel.org,
        Hector Martin <marcan@...can.st>, linux-kernel@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>,
        Mohamed Mediouni <mohamed.mediouni@...amail.com>,
        Stan Skowronek <stan@...ellium.com>,
        linux-arm-kernel@...ts.infradead.org,
        Mark Kettenis <mark.kettenis@...all.nl>,
        iommu@...ts.linux-foundation.org, Alexander Graf <graf@...zon.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Rob Herring <robh+dt@...nel.org>, r.czerwinski@...gutronix.de
Subject: Re: [PATCH v4 3/3] iommu: dart: Add DART iommu driver

Looks really good! Just a few minor comments. With them addressed,

	Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>

> +	  Say Y here if you are using an Apple SoC with a DART IOMMU.

Nit: Do we need to spell out "with a DART IOMMU"? Don't all the apple
socs need DART?

> +/*
> + * This structure is used to identify a single stream attached to a domain.
> + * It's used as a list inside that domain to be able to attach multiple
> + * streams to a single domain. Since multiple devices can use a single stream
> + * it additionally keeps track of how many devices are represented by this
> + * stream. Once that number reaches zero it is detached from the IOMMU domain
> + * and all translations from this stream are disabled.
> + *
> + * @dart: DART instance to which this stream belongs
> + * @sid: stream id within the DART instance
> + * @num_devices: count of devices attached to this stream
> + * @stream_head: list head for the next stream
> + */
> +struct apple_dart_stream {
> +	struct apple_dart *dart;
> +	u32 sid;
> +
> +	u32 num_devices;
> +
> +	struct list_head stream_head;
> +};

It wasn't obvious to me why we can get away without reference counting.
Looking ahead it looks like we assert locks in each case. Maybe add
that to the comment?

```
> +static void apple_dart_hw_set_ttbr(struct apple_dart *dart, u16 sid, u16 idx,
> +				   phys_addr_t paddr)
> +{
> +	writel(DART_TTBR_VALID | (paddr >> DART_TTBR_SHIFT),
> +	       dart->regs + DART_TTBR(sid, idx));
> +}
```

Should we be checking alignment here? Something like

    BUG_ON(paddr & ((1 << DART_TTBR_SHIFT) - 1));