RE: [PATCH 1/1] scsi: storvsc: Fix swiotlb bounce buffer leak in confidential VM

[Dexuan Cui]

> From: Michael Kelley (LINUX) <mikelley@xxxxxxxxxxxxx>
> Sent: Sunday, December 4, 2022 11:53 AM
> 
> 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.
> 
> Fix this by doing scsi_dma_unmap() in the case of an I/O submission
> error, which frees the bounce buffer memory.
> 
> Fixes: 743b237c3a7b ("scsi: storvsc: Add Isolation VM support for storvsc
> driver")
> Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> ---

Reviewed-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
Tested-by: Dexuan Cui <decui@xxxxxxxxxxxxx>

I hope this fix can be included in v6.1.