Re: [PATCH v2 1/3] memory: Track whether a Device is engaged in IO

[David Hildenbrand <david@redhat.com>]

On 27.05.22 18:19, Alexander Bulekov wrote:
> Add a flag to the DeviceState, when a device is engaged in PIO/MMIO/DMA.
> This flag should be set/checked prior to calling a device's MemoryRegion
> handlers, and set when device code initiates DMA.  The purpose of this
> flag is to prevent DMA reentrancy issues. E.g.:
> sdhci pio -> dma write -> sdhci mmio
> nvme bh -> dma write -> nvme mmio
> 
> These issues have led to problems such as stack-exhaustion and
> use-after-frees.
> 
> Assumptions:
>  * Devices do not interact with their own PIO/MMIO memory-regions using
>    DMA.
> 
>  * There is now way for there to be multiple simultaneous accesses to a
>    device's PIO/MMIO memory-regions, or for multiple threads to perform
>    DMA accesses simultaneously on behalf of a single device.
> 
> Signed-off-by: Alexander Bulekov <alxndr@bu.edu>

I think this patch should be squashed into the other ones, it doesn't
make particular sense without any actual users.


-- 
Thanks,

David / dhildenb