Re: [Qemu-devel] [PATCH] memory.h: Improve IOMMU related documentation

[Paolo Bonzini]

On 30/04/2018 15:34, Peter Maydell wrote:
>>       */
>>      IOMMUTLBEntry (*translate)(IOMMUMemoryRegion *iommu, hwaddr addr,
>>                                 IOMMUAccessFlags flag);
> A question I just thought of -- how long is the IOMMUTLBEntry I get
> back guaranteed to be valid for? For instance if I'm in an RCU
> critical section can I assume it won't become invalid before I
> leave the critical section? Or must I always register an IOMMU
> notifier before I call translate? I'm guessing not the latter
> because flatview_do_translate() does not, but is the guarantee
> only RCU-critical section or while-holding-big-QEMU-lock or
> something else?

The only pointer inside is to the target AddressSpace, which (see
address_space_destroy) is safe to access inside either of those
condition.  In practice we use the former.

Paolo