Hi Yes, my host card is the integrated Intel. I patched the kernel at first, to work with VGA arbitration, when I started virtualizing Windows 7 with BIOS. Then, I successfully switched to Windows 8 (and Windows 10) and UEFI so that I could just use a stock kernel. I had to use a ROM file for the NVIDIA card because it did not support UEFI, but that also worked flawlessly.
The x-vga=on param is there because I tested it and forgot to remove it. Nevertheless, it had no effect. In any case, the successful attempts were made with a commit from the 2.2 branch with the NoSnoop patch. The commit without the patch, and any commit I tested from version 2.3 to 2.8, all fail. Anyway this was more an exercise than an actual issue, since I have a working configuration, but maybe it helps you find some bug. Is there anything else you want me to try? Thanks Javi 2017-01-30 21:19 GMT+01:00 Alex Williamson <[email protected]>: > On Sun, 29 Jan 2017 23:03:38 +0100 > Javier Celaya <[email protected]> wrote: > > > The host kernel is version 4.9.0 from Debian Sid. That command outputs > > "f0105a". What does it mean? > > Bit 7 would indicate if the IOMMU supports Snoop Control. When it > does, the IOMMU page tables can set the SNP bit, which allows > transactions to snoop the processor cache regardless of transaction > attributes such as NoSnoop. IOW, it basically negates NoSnoop at the > IOMMU level. Since this bit is clear on your IOMMU, we need to > register non-coherent DMA with KVM. This affects memory attributes in > a few places and determines whether or not KVM needs to emulate the > WBINVD (write-back-invalidate) instruction. To some extent, we do need > to trust guest memory attributes to work in this mode, however the > NoSnoop patch, which simply tries to prevent the device from enabling > NoSnoop transactions was a pretty horrible hack. > > I'm sure that lots of us run with the same IOMMU capabilities, I have a > system with identical flags that runs without issue with either an > NVIDIA or AMD card. I wonder if the problem is more to do with the > fact that your CPU has integrated graphics and you're trying to use > x-vga=on without any mention whether you've patched i915 to properly > work with VGA arbitration. If the cards support UEFI, you should not > need x-vga=on. Is the host primary graphics Intel? I don't understand > why the NoSnoop patch would change your results at all. Thanks, > > Alex >
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