daggs
2020-Nov-17 10:32 UTC
image works in native but not in vm when cpu mode='host-passthrough' is set
Greetings. I have an image I've created with a bunch of chost flags which works on my machine when it comes to native boot. if I take that same image into a vm managed via libvirt, I get kernel panic. I'd assume that something is missing from my vm config, question is what and what I can do about it? here is the flags part of lscpu in native and vm: https://dpaste.com/3TR8QJ5G8 and the vm's xml: https://dpaste.com/984JX4LUQ if I build the image with the default flags (march=x86-64), the vm boots well. my new chost is -O2 -pipe -march=skylake -mabm -mno-adx -mno-avx -mno-avx2 -mno-bmi -mno-bmi2 -mno-f16c -mno-fma -mno-xsave -mno-xsavec -mno-xsaveopt -mno-xsaves -mno-sgx the cpu is Intel(R) Pentium(R) CPU G4560 @ 3.50GHz thoughts? Thanks, Dagg.
Martin Kletzander
2020-Nov-19 21:23 UTC
Re: image works in native but not in vm when cpu mode='host-passthrough' is set
On Tue, Nov 17, 2020 at 11:32:29AM +0100, daggs wrote:>Greetings. > >I have an image I've created with a bunch of chost flags which works on my machine when it comes to native boot. >if I take that same image into a vm managed via libvirt, I get kernel panic. >I'd assume that something is missing from my vm config, question is what and what I can do about it? >here is the flags part of lscpu in native and vm: https://dpaste.com/3TR8QJ5G8 >and the vm's xml: https://dpaste.com/984JX4LUQ >if I build the image with the default flags (march=x86-64), the vm boots well. >my new chost is -O2 -pipe -march=skylake -mabm -mno-adx -mno-avx -mno-avx2 -mno-bmi -mno-bmi2 -mno-f16c -mno-fma -mno-xsave -mno-xsavec -mno-xsaveopt -mno-xsaves -mno-sgx >the cpu is Intel(R) Pentium(R) CPU G4560 @ 3.50GHz >Not sure, but there might be some flags that are not passed through even with host-passthrough. Virtualisation ones are definitely one of those that need to be enabled on top of host-passthrough. The easiest thing to check that I can think of would be booting some live distro and checking the flags in /proc/cpuinfo and how are they different from your host.>thoughts? > >Thanks, > >Dagg. >
daggs
2020-Nov-20 07:06 UTC
Re: image works in native but not in vm when cpu mode='host-passthrough' is set
Greetings Martin,> Sent: Thursday, November 19, 2020 at 11:23 PM > From: "Martin Kletzander" <mkletzan@redhat.com> > To: "daggs" <daggs@gmx.com> > Cc: "libvirt-usersredhat.com" <libvirt-users@redhat.com> > Subject: Re: image works in native but not in vm when cpu mode='host-passthrough' is set > > On Tue, Nov 17, 2020 at 11:32:29AM +0100, daggs wrote: > ... > Not sure, but there might be some flags that are not passed through even with > host-passthrough. Virtualisation ones are definitely one of those that need to > be enabled on top of host-passthrough. The easiest thing to check that I can > think of would be booting some live distro and checking the flags in > /proc/cpuinfo and how are they different from your host. >I don't need livecd, I can diff both native and vm, see https://dpaste.com/ARETBEPCL from what I can see, the vm is missing these flags: dts acpi tm pbe art pebs bts nonstop_tsc aperfmperf dtes64 monitor ds_cpl est tm2 sdbg xtpr pdcm epb intel_pt dtherm pln pts hwp hwp_notify hwp_act_window hwp_epp and have these flags: tsc_known_freq hypervisor umip arch_capabilities beside the acpi flag which I found strange to be messing, I can't think of any other flag which might be needed. Dagg.
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