linux-kernel - Re: [PATCH 1/1] scsi: storvsc: Fix swiotlb bounce buffer leak in confidential VM

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Message-ID: <yq1r0x2eltj.fsf@ca-mkp.ca.oracle.com>
Date:   Tue, 13 Dec 2022 21:55:13 -0500
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     kys@...rosoft.com, martin.petersen@...cle.com,
        longli@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com,
        jejb@...ux.ibm.com, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: [PATCH 1/1] scsi: storvsc: Fix swiotlb bounce buffer leak in
 confidential VM


Michael,

> storvsc_queuecommand() maps the scatter/gather list using scsi_dma_map(),
> which in a confidential VM allocates swiotlb bounce buffers. If the
> I/O submission fails in storvsc_do_io(), the I/O is typically retried
> by higher level code, but the bounce buffer memory is never freed.
> The mostly like cause of I/O submission failure is a full VMBus
> channel ring buffer, which is not uncommon under high I/O loads.
> Eventually enough bounce buffer memory leaks that the confidential
> VM can't do any I/O. The same problem can arise in a non-confidential
> VM with kernel boot parameter swiotlb=force.

Applied to 6.2/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering