Re: [edk2] DMA memory regions and device behavior

Subject: Re: [edk2] DMA memory regions and device behavior

From: "Kinney, Michael D" <michael.d.kinney@intel.com>

To: "edk2-devel@lists.sourceforge.net" <edk2-devel@lists.sourceforge.net>

Date: 2014-01-25 02:44:16

Stephen,

A memory stress test can only be run on memory regions that are allocated using AllocatePages() or AllocatePool().

Drivers that use DMA will allocate memory for the DMA buffers.  Those buffers show up in the EFI Memory Map through the GetMemoryMap() API as allocated regions.

Best regards,

Mike

-----Original Message-----
From: Stephen Polkowski [mailto:stephen@centtech.com] 
Sent: Friday, January 24, 2014 9:56 AM
To: edk2-devel@lists.sourceforge.net
Subject: [edk2] DMA memory regions and device behavior

UEFI gurus,

	Does UEFI have an api for querying the DMA regions in
the memory system?  I would like to know where they are.
I need to write a memory stress test shell application.
The application will need to read/write all the DRAM with patterns.

	I am worried that it will hit a usb or network buffer while a DMA
is in progress.  Can I assume that there will be no DMAs until I
make a read or write call to a UEFI device?

	To put it another way, if my application is running in it's own code
segment, can I assume that their are no DMAs happening simultaneously?

Thanks for your help.


Stephen


-- 
Stephen Polkowski
Centaur Technology
Austin, TX
(512) 418-5730

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