Re: [Xen-devel] memory map issues with PV PCI passthrough

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 12/08/2011 09:47 AM, Ian Campbell wrote:
> On Thu, 2011-12-08 at 14:39 +0000, Daniel De Graaf wrote:
>> I have a system with several reserved ranges low in the e820 map which
>> cause problems when starting PV domains with PCI devices. The machine
>> memory map looks like:
>>
>> (XEN)  0000000000000000 - 0000000000060000 (usable)
>> (XEN)  0000000000060000 - 0000000000068000 (reserved)
>> (XEN)  0000000000068000 - 000000000009ac00 (usable)
>> (XEN)  000000000009ac00 - 00000000000a0000 (reserved)
>> (XEN)  00000000000e0000 - 0000000000100000 (reserved)
>> (XEN)  0000000000100000 - 0000000000800000 (usable)
>> (XEN)  0000000000800000 - 000000000087d000 (unusable)
>> (XEN)  000000000087d000 - 0000000000f00000 (usable)
>> (XEN)  0000000000f00000 - 0000000001000000 (reserved)
>> (XEN)  0000000001000000 - 0000000020000000 (usable)
>> (XEN)  0000000020000000 - 0000000020200000 (reserved)
>> (XEN)  0000000020200000 - 0000000040000000 (usable)
>> (XEN)  0000000040000000 - 0000000040200000 (reserved)
>> (XEN)  0000000040200000 - 00000000c95d6000 (usable)
>> (XEN)  00000000c95d6000 - 00000000c961a000 (reserved)
>> (XEN)  00000000c961a000 - 00000000c99b7000 (usable)
>> (XEN)  00000000c99b7000 - 00000000c99e7000 (reserved)
>> (XEN)  00000000c99e7000 - 00000000c9be7000 (ACPI NVS)
>> (XEN)  00000000c9be7000 - 00000000c9bff000 (ACPI data)
>> (XEN)  00000000c9bff000 - 00000000c9c00000 (usable)
>> (XEN)  00000000c9f00000 - 00000000ca000000 (reserved)
>> (XEN)  00000000cb000000 - 00000000cf200000 (reserved)
>> (XEN)  00000000fed1c000 - 00000000fed30000 (reserved)
>> (XEN)  00000000ffc00000 - 00000000ffc20000 (reserved)
>> (XEN)  0000000100000000 - 000000042e000000 (usable)
>>
>> When e820_sanitize is called on this memory map to create a PV domain, the
>> resulting map has only one usable region (0-0xf00000) below 4GB, and Linux
>> will not boot with this memory map.
> 
> Are you using xl's e820_host option?
> 
> Ian.
> 
> 
Yes, since enabling PCI passthrough in a PV guest enables this.

-- 
Daniel De Graaf
National Security Agency

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