* CONFIG_HIGHMEM or CONFIG_HIGHMEM64G in illegal_highdma()
@ 2008-05-06 12:35 Marin Mitov
0 siblings, 0 replies; 2+ messages in thread
From: Marin Mitov @ 2008-05-06 12:35 UTC (permalink / raw)
To: linux-kernel; +Cc: netdev
Hi all,
The usage of NETIF_F_HIGHDMA in net drivers make me think its
purpose is to declare drivers's capability to address RAM above 4GB, OK?
For x86_64 CONFIG_HIGHMEM is not defined, so the function
illegal_highdma() found in net/core/dev.c returns 0 because
x86_64 has IOMMU mapping all RAM.
For x86_32 CONFIG_HIGHMEM is defined as
(CONFIG_HIGHMEM4G || CONFIG_HIGHMEM64G)
While CONFIG_HIGHMEM4G insures RAM is bellow 4GB some checks
are unnecessarily done.
Should we have CONFIG_HIGHMEM64G in illegal_highdma()
instead of CONFIG_HIGHMEM?
Regards.
Marin Mitov
^ permalink raw reply [flat|nested] 2+ messages in thread
* CONFIG_HIGHMEM or CONFIG_HIGHMEM64G in illegal_highdma()
@ 2008-05-07 16:49 Marin Mitov
0 siblings, 0 replies; 2+ messages in thread
From: Marin Mitov @ 2008-05-07 16:49 UTC (permalink / raw)
To: linux-kernel; +Cc: netdev
Hi all,
The usage of NETIF_F_HIGHDMA in drivers/net/* make me think its
purpose is to declare drivers's capability to address RAM above 4GB, OK?
For x86_64 CONFIG_HIGHMEM is not defined, so the function
illegal_highdma() found in net/core/dev.c returns 0 because
x86_64 has IOMMU mapping all RAM.
For x86_32 CONFIG_HIGHMEM is defined as
(CONFIG_HIGHMEM4G || CONFIG_HIGHMEM64G)
While CONFIG_HIGHMEM4G insures RAM is bellow 4GB some checks
are unnecessarily done.
Should we have CONFIG_HIGHMEM64G in illegal_highdma()
instead of CONFIG_HIGHMEM? If so should I post a patch?
Regards.
Marin Mitov
P.S. This is a resend, due to recent problems with http://lkml.org/
^ permalink raw reply [flat|nested] 2+ messages in thread
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