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Date:   Wed, 5 Apr 2023 06:40:19 +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: <20230405064019.6258ebb3@meshulam.tesarici.cz>
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Hi Dexuan,

On Tue, 4 Apr 2023 20:11:18 +0000
Dexuan Cui <decui@microsoft.com> wrote:

> > From: Dexuan-Linux Cui <dexuan.linux@gmail.com>
> > Sent: Tuesday, April 4, 2023 12:55 PM
> >=20
> > On Tue, Mar 21, 2023 at 1:37=E2=80=AFAM Petr Tesarik
> > <petrtesarik@huaweicloud.com> wrote:
> > ...
> >=20
> > Hi Petr, this patch has gone into the mainline:
> > 0eee5ae10256 ("swiotlb: fix slot alignment checks")
> >=20
> > Somehow it breaks Linux VMs on Hyper-V: a regular VM with
> > swiotlb=3Dforce or a confidential VM (which uses swiotlb) fails to boot.
> > If I revert this patch, everything works fine. =20
>=20
> The log is pasted below. Looks like the SCSI driver hv_storvsc fails to
> detect the disk capacity:

The first thing I can imagine is that there are in fact no (free) slots
in the SWIOTLB which match the alignment constraints, so the map
operation fails. However, this would result in a "swiotlb buffer is
full" message in the log, and I can see no such message in the log
excerpt you have posted.

Please, can you check if there are any "swiotlb" messages preceding the
first error message?

Petr T