On Thu, Dec 21, 2017 at 10:56:38AM +0000, Chris Wilson wrote: > Quoting Du, Changbin (2017-12-21 09:52:16) > > Hi Chris, > > Our QA reported a problem caused by movntdqa instructions. Currently, the KVM > > hypervisor doesn't support VEX-prefix instructions emulation. If users passthrough > > a GPU to guest with vfio option 'x-no-mmap=on', then all access to the BARs will > > be trapped and emulated. The KVM hypervisor would raise an inertal error to qemu > > which cause the guest killed. (Since 'movntdqa' ins is not supported.) > > > > One possible solution is that disable this optimization at i915_memcpy_init_early. > > This require us to identify the CPUID to check if it is running in guest mode. > > Is this mode not detected by intel_vgpu_active() ? > Here intel_vgpu_active() is not ready to use. i915_memcpy_init_early is executed before MMIO mapped. > If we need to disable movntdqa, we need to disable it. But not by > directly checking CPUID, it should be already decoded into a cpu feature > flag -- assuming we need more than intel_vgpu_active and possibly > rearranging the init order. > -Chris Yes, for Intel CPU, Bit 31 of ECX of CPUID leaf 0x1 is Hypervisor Present Bit. So I will write a patch to disable it in hypervisor guest if you don't have objections. Thanks. -- Thanks, Changbin Du _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
