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]<mailto:[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]<mailto:[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]<http://gmail.com>]
Sent: Wednesday, May 15, 2013 4:16 PM
To: [email protected]<mailto:[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]<mailto:[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]<mailto:[email protected]>]
Sent: Tuesday, May 14, 2013 10:17 AM
To: [email protected]<mailto:[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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