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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] HVM support for e820_host (Was: Bug: Limitation of <=2GB RAM in domU persists with 4.3.0)
On Fri, 6 Sep 2013 09:09:06 -0400, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote: On Thu, Sep 05, 2013 at 11:42:38PM +0100, Gordan Bobic wrote:On 09/05/2013 11:23 PM, Konrad Rzeszutek Wilk wrote: >Gordan Bobic <gordan@xxxxxxxxxx> wrote: >>Right, finally got around to trying this with the latest patch. >> >>With e820_host=0 things work as before: >> >>(XEN) HVM3: BIOS map: >>(XEN) HVM3: f0000-fffff: Main BIOS >>(XEN) HVM3: E820 table: >>(XEN) HVM3: [00]: 00000000:00000000 - 00000000:0009e000: RAM >>(XEN) HVM3: [01]: 00000000:0009e000 - 00000000:000a0000: RESERVED >>(XEN) HVM3: HOLE: 00000000:000a0000 - 00000000:000e0000 >>(XEN) HVM3: [02]: 00000000:000e0000 - 00000000:00100000: RESERVED >>(XEN) HVM3: [03]: 00000000:00100000 - 00000000:e0000000: RAM >>(XEN) HVM3: HOLE: 00000000:e0000000 - 00000000:fc000000 >>(XEN) HVM3: [04]: 00000000:fc000000 - 00000001:00000000: RESERVED >>(XEN) HVM3: [05]: 00000001:00000000 - 00000002:1f800000: RAM >> >>>>I seem to be getting two different E820 table dumps with e820_host=1:>> >>(XEN) HVM1: BIOS map: >>(XEN) HVM1: f0000-fffff: Main BIOS >>(XEN) HVM1: build_e820_table:91 got 8 op.nr_entries >>(XEN) HVM1: E820 table: >>(XEN) HVM1: [00]: 00000000:00000000 - 00000000:3f790000: RAM >>(XEN) HVM1: [01]: 00000000:3f790000 - 00000000:3f79e000: ACPI >>(XEN) HVM1: [02]: 00000000:3f79e000 - 00000000:3f7d0000: NVS >>(XEN) HVM1: [03]: 00000000:3f7d0000 - 00000000:3f7e0000: RESERVED >>(XEN) HVM1: HOLE: 00000000:3f7e0000 - 00000000:3f7e7000 >>(XEN) HVM1: [04]: 00000000:3f7e7000 - 00000000:40000000: RESERVED >>(XEN) HVM1: HOLE: 00000000:40000000 - 00000000:fee00000 >>(XEN) HVM1: [05]: 00000000:fee00000 - 00000000:fee01000: RESERVED >>(XEN) HVM1: HOLE: 00000000:fee01000 - 00000000:ffc00000 >>(XEN) HVM1: [06]: 00000000:ffc00000 - 00000001:00000000: RESERVED >>(XEN) HVM1: [07]: 00000001:00000000 - 00000001:68870000: RAM >>(XEN) HVM1: E820 table: >>(XEN) HVM1: [00]: 00000000:00000000 - 00000000:0009e000: RAM >>(XEN) HVM1: [01]: 00000000:0009e000 - 00000000:000a0000: RESERVED >>(XEN) HVM1: HOLE: 00000000:000a0000 - 00000000:000e0000 >>(XEN) HVM1: [02]: 00000000:000e0000 - 00000000:00100000: RESERVED >>(XEN) HVM1: [03]: 00000000:00100000 - 00000000:a7800000: RAM >>(XEN) HVM1: HOLE: 00000000:a7800000 - 00000000:fc000000 >>(XEN) HVM1: [04]: 00000000:fc000000 - 00000001:00000000: RESERVED >>(XEN) HVM1: Invoking ROMBIOS ... >>>>I cannot quite figure out what is going on here - these tables can't>>both be true. >> >>Right. The code just prints the E820 that was constructed b/c of the e820_host =1 parameter as the first output. Then the second one is what was constructed originally.>>The code that would tie in the E820 from the hyper call and the alter how the hvmloader sets it up is not yet done.> >>>Looking at the IOMEM on the host, the IOMEM begins at 0xa8000000 and>>goes more or less contiguously up to 0xfec8b000. >>>>Looking at dmesg on domU, the e820 map more or less matches the second>>dump above. >>Right. That is correct since the patch I sent just outputs stuff. No real changes to the E820 yet./me *facepalms* That indeed explains everything. :) But having had a thorough look through the memory mappings (see my other long, rambling email), I don't actually see an obvious area where RAM might overwrite a dom0 IOMEM range - assuming the "HOLE" part isn't mapped as RAM in domU. Or to summarize: dom0 PCI IOMEM actually has mappings from a8000000 onward, and giving domU up to that much memory works fine. So the memory stomp must be happening from a8000000 onward. But - the only things above that address in domU are the HOLE up to fc000000 and RESERVED up to ffffffff. So no domU memory is getting mapped into the IOMEM range anyway - which begs the question of what is _actually_ causing the crash. Stuff I haven't yet found in domU getting mapped into the a7800000-fc000000 hole overlapping dom0 IOMEM? SeaBIOS doing smething odd in the fc000000-fec8b000 range marked RESERVED in domU?There were some assumptions with that region and that stuff could be stick in there (like ACPI tables and SMBIOS I think).Perhaps a better question is - are any of the BARs of your card overlappingwith the RESERVED range in the domU?Or if you grep through the hvmloader code are there anything addressesthat look to be within that range?Incidentally could you send the output of lspci -vvvv from your outputin the guest and in dom0 please? Attached. The main point I'm trying to keep in mind here is that this needs to be generic and useful in different hardware cases, not just my own. If it were just about my own hardware and use case I'd have just opted for the approach of the old vBAR-pBAR patch, hard-coded the holes and been done with it. Or am I reading this all wrong?You are on the right track I think. There is some assumption made about the RESERVED and HOLE that I think are conflicing with what thecard thinks of. Another way to figure out what is happening is to crankup the verbosity of the driver in the domU. Specifically there is an CONFIG_MMIO_TRACE (or something like that) that will tell you thephysical address the PCI cards are using and what it is writting in it.It could help in identifying _where_ the graphic card is writting/readingfrom. And also the last moment when it wrote something. That's a part of my problem - my domU with a reproducible crash is Windows which is a lot less debuggable. :( I have a Linux domU that I use for figuring out what the domU looks like from the inside, but I don't have a readily usable test-case for reproducing the crash there. Gordan Attachment:
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