Did you mark the memory region as EFI_MEMORY_RUNTIME. This should force the OS 
to give you a kernel virtual address for this region, and implies that firmware 
may access it at runtime.

Andrew Fish





On May 15, 2013, at 4:11 PM, "Prakash, Sathya" <[email protected]> wrote:

> Chip,
> Thanks for the response, I am able to pass the address through my controller 
> firmware (UEFI driver and OS driver can handshake with controller firmware 
> for the address) but my question is, is it legal to access.  I am seeing some 
> issues when IOMMU comes into picture, it consider the address is reserved 
> (from memory map) and faults the access from my OS driver.
>  
> Thanks
> Sathya
>  
> From: Chip Ueltschey [mailto:[email protected]] 
> Sent: Wednesday, May 15, 2013 4:16 PM
> To: [email protected]
> Subject: Re: [edk2] Memory reserved using EfiRuntimeServicesData and IOMMU
>  
> Sathya,
>  
> You need a way to pass the address to your OS. The memory is already there.
> You could use a variable, but you need to have a pointer to variable services.
> You can store the information in ASL. Non-trivial to make this work, but I 
> know that it is possible to do.
>  
> -chip
>  
> 
> On Tue, May 14, 2013 at 4:16 PM, Prakash, Sathya <[email protected]> 
> wrote:
> Just to clarify further. Are we allowed to access the memory allocated by our 
> UEFI driver as RuntimeServiceData in our OS drivers (the physical address is 
> passed by the uefi driver to controller and controller to OS driver)?
> 
> Thanks
> Sathya
> 
> -----Original Message-----
> From: Prakash, Sathya [mailto:[email protected]]
> Sent: Tuesday, May 14, 2013 10:17 AM
> To: [email protected]
> Subject: [edk2] Memory reserved using EfiRuntimeServicesData and IOMMU
> 
> Folks,
> We allocate some host memory as EfiRuntimeServicesData and utilize the memory 
> in host driver for a certain purpose. This works fine with normal cases, but 
> will it work with IOMMU?. I see the IOMMU module in linux needs to know about 
> the reserved regions through RMRR address table to map the access, does the 
> GetMemoryMap supports this?
> 
> Thanks
> Sathya
> 
> 
> 
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