Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 5 Apr 2023 08:07:03 +0200
From:   Petr =?UTF-8?B?VGVzYcWZw61r?= <petr@tesarici.cz>
To:     Dexuan Cui <decui@microsoft.com>
Cc:     Dexuan-Linux Cui <dexuan.linux@gmail.com>,
        Petr Tesarik <petrtesarik@huaweicloud.com>,
        Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Jianxiong Gao <jxgao@google.com>,
        David Stevens <stevensd@chromium.org>,
        Joerg Roedel <jroedel@suse.de>,
        "open list:DMA MAPPING HELPERS" <iommu@lists.linux.dev>,
        open list <linux-kernel@vger.kernel.org>,
        Roberto Sassu <roberto.sassu@huawei.com>,
        "Michael Kelley (LINUX)" <mikelley@microsoft.com>,
        Tianyu Lan <Tianyu.Lan@microsoft.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>
Subject: Re: [PATCH v1 2/2] swiotlb: Fix slot alignment checks
Message-ID: <20230405080703.61c6d60a@meshulam.tesarici.cz>
In-Reply-To: <SA1PR21MB1335CF4B7E9B1EC61B84AA03BF909@SA1PR21MB1335.namprd21.prod.outlook.com>
References: <cover.1679382779.git.petr.tesarik.ext@huawei.com>
        <c90887e4d75344abe219cc5e12f7c6dab980cfce.1679382779.git.petr.tesarik.ext@huawei.com>
        <CAA42JLa1y9jJ7BgQvXeUYQh-K2mDNHd2BYZ4iZUz33r5zY7oAQ@mail.gmail.com>
        <CO1PR21MB13320305E02BA121623213DABF939@CO1PR21MB1332.namprd21.prod.outlook.com>
        <20230405064019.6258ebb3@meshulam.tesarici.cz>
        <SA1PR21MB1335C5F774195F2C3431BF93BF909@SA1PR21MB1335.namprd21.prod.outlook.com>
        <20230405072801.05bb94ef@meshulam.tesarici.cz>
        <20230405075034.3c36bb77@meshulam.tesarici.cz>
        <SA1PR21MB1335CF4B7E9B1EC61B84AA03BF909@SA1PR21MB1335.namprd21.prod.outlook.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Wed, 5 Apr 2023 06:00:13 +0000
Dexuan Cui <decui@microsoft.com> wrote:

> > From: Petr Tesa=C5=99=C3=ADk <petr@tesarici.cz>
> > Sent: Tuesday, April 4, 2023 10:51 PM =20
> > > ...
> > > Argh, you're right. This is a braino. The alignment mask is in fact an
> > > INVERTED mask, i.e. it masks off bits that are not relevant for the
> > > alignment. The more strict alignment needed the more bits must be set,
> > > so the individual alignment constraints must be combined with an OR
> > > instead of an AND.
> > >
> > > Can you apply the following change and check if it fixes the issue? =
=20
> >=20
> > Actually, this will not work either. The mask is used to mask off both =
=20
> It works for me.

Yes, as long as the original (non-bounced) address is aligned at least
to a 2K boundary, it appears to work. ;-)

> > high address bits and low address bits (below swiotlb slot granularity).
> >=20
> > What should help is this:
> > ... =20
> This also works for me.
>=20
> Thanks, *either* version can resolve the issue for me :-)

Thank you for testing! I will write a proper commit message and submit
a fix. Embarassing... *sigh*

Can I add your Tested-by?

Petr T