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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] cpuid problem in upstream qemu with kvm |
Date: | Mon, 14 Dec 2009 15:49:39 -0600 |
User-agent: | Thunderbird 2.0.0.23 (X11/20090825) |
Michael S. Tsirkin wrote:
On Mon, Dec 14, 2009 at 02:54:49PM -0600, Anthony Liguori wrote:Michael S. Tsirkin wrote:That's a kernel bug. If we think it effects a lot of users, we should introduce a CAP such that we can detect this in userspace and fail gracefully.On Mon, Dec 14, 2009 at 02:18:33PM -0600, Anthony Liguori wrote:Michael S. Tsirkin wrote:This might help 32 bit guests, but not guests with 64 bit kernel and 32 bit userspace (my case) because all 64 bit CPUs advertise syscall bit in cpuid. Thus 64 bit guests do not seem to even bother checking this bit: AMD + 64 bit -> syscall.Okay, I don't see a great option other than migrating the vendor_id string.This won't help with kernels <2.6.32 though. I guess we can switch default vendor to Intel, this likely has some other side effects.Not emulating feature host CPU does not have is a kernel bug? Okay ... Yes, almost no one runs 2.6.32 yet.
The kernel has the ability to filter feature bits from cpuid. We assume it's going to filter out things it doesn't support.
Regards, Anthony Liguori
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