You can check the EFI memory map to see if the EFI_MEMORY_RUNTIME is set. You
should get a virtual mapping from the OS. Are you using the virtual address
provided by the OS for the access?
Andrew Fish
On May 16, 2013, at 9:09 AM, "Prakash, Sathya" <[email protected]> wrote:
> Thanks Mike, We understand the risk and we are trying to move away from this
> model.
>
> Andrew, The Memory is allocated using the below call, will it not
> automatically set the region internally as EFI_MEMORY_RUNTIME?
>
> gBS->AllocatePages(X, EfiRuntimeServicesData, Sz, &MemoryToDrvr);
>
> This doesn’t cause any issue in a system in which IOMMU (Vt-d) is not
> enabled, but when IOMMU is enabled accessing this address creates fault.
>
> Do you mean to say we need to explicitly set the memory descriptor type using
> GetMemorySpaceDescriptor and SetMemorySpaceAttributes?
>
>
> Thanks
> Sathya
>
> From: Kinney, Michael D [mailto:[email protected]]
> Sent: Wednesday, May 15, 2013 7:05 PM
> To: [email protected]; Kinney, Michael D
> Subject: Re: [edk2] Memory reserved using EfiRuntimeServicesData and IOMMU
>
> Sathya,
>
> In general, this technique can be problematic. UEFI Drivers are not required
> to run every boot. If your OS driver depends on the UEFI Driver running,
> then the OS Driver may fail. It is better if the OS Driver does not depend
> on information from the UEFI Driver.
>
> Mike
>
>
>
> From: Andrew Fish [mailto:[email protected]]
> Sent: Wednesday, May 15, 2013 4:15 PM
> To: [email protected]
> Subject: Re: [edk2] Memory reserved using EfiRuntimeServicesData and IOMMU
>
> 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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