Re: [Xen-devel] [PATCH] iomem: Prevent Dom0 pci bus from allocating RAM as I/O space

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Feb 16, 2011 at 10:06:38AM -0500, Konrad Rzeszutek Wilk wrote:
> On Wed, Feb 16, 2011 at 10:26:20PM +0800, Zhang, Fengzhe wrote:
> > iomem: Prevent Dom0 pci bus from allocating RAM as I/O space
> 
> Is there a bug # associated with this? Is this associated with the intel-agp
> driver trying to ioremap the scratch page and bombing out?
> 
> > 
> > In Dom0, pci bus dynamically allocates I/O address resources from memory 
> > hole within 4GB physical space, which can be RAM space not allocated to 
> > Dom0. This patch set physical RAM space to be unusable in Dom0 E820 map if 
> > they are not owned by Dom0 to prevent them from being misused as I/O 
> > address space. Dom0 is assumed to look for MMIO space only below 4GB. If 
> > this assumption is broken, additional fixes are required.
> 
> You mention "RAM space" and then "physical RAM" misused as "I/O" address 
> space.

Hmm, is the issue that we have this E820:

(XEN)  000000000009d000 - 00000000000a0000 (reserved)^M
(XEN)  00000000000e0000 - 0000000000100000 (reserved)^M
(XEN)  0000000000100000 - 000000009cf67000 (usable)^M
(XEN)  000000009cf67000 - 000000009d103000 (ACPI NVS)^M
(XEN)  000000009d103000 - 000000009f6bd000 (usable)^M
(XEN)  000000009f6bd000 - 000000009f6bf000 (reserved)^M
(XEN)  000000009f6bf000 - 000000009f714000 (usable)^M
(XEN)  000000009f714000 - 000000009f7bf000 (ACPI NVS)^M
(XEN)  000000009f7bf000 - 000000009f7e0000 (usable)^M
(XEN)  000000009f7e0000 - 000000009f7ff000 (ACPI data)^M
(XEN)  000000009f7ff000 - 000000009f800000 (usable)^M
(XEN)  000000009f800000 - 00000000a0000000 (reserved)^M

with System RAM regions sprinkled around the reserved and when
you use dom0_mem=1GB, the setup.c has made those regions size 0
(by subtracting the delta), so that when e820_santize gets called it
will remove them altogether and end up converting those areas in gaps,
as so:

[    0.000000] BIOS-provided physical RAM map:^M^M
[    0.000000]  Xen: 0000000000000000 - 000000000009d000 (usable)^M^M
[    0.000000]  Xen: 000000000009d000 - 0000000000100000 (reserved)^M^M
[    0.000000]  Xen: 0000000000100000 - 0000000040000000 (usable)^M^M
[    0.000000]  Xen: 000000009cf67000 - 000000009d103000 (ACPI NVS)^M^M
[    0.000000]  Xen: 000000009f6bd000 - 000000009f6bf000 (reserved)^M^M
[    0.000000]  Xen: 000000009f714000 - 000000009f7bf000 (ACPI NVS)^M^M
[    0.000000]  Xen: 000000009f7e0000 - 000000009f7ff000 (ACPI data)^M^M
[    0.000000]  Xen: 000000009f800000 - 00000000b0000000 (reserved)^M^M
[    0.000000]  Xen: 00000000fc000000 - 00000000fd000000 (reserved)^M^M
[    0.000000]  Xen: 00000000fec00000 - 00000000fec01000 (reserved)^M^M
[    0.000000]  Xen: 00000000fee00000 - 00000000fee01000 (reserved)^M^M
[    0.000000]  Xen: 00000000ffe00000 - 0000000100000000 (reserved)^M^M
[    0.000000]  Xen: 0000000100000000 - 00000001bf598000 (usable)^M^M

?

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel