Re: [Xen-devel] [PATCH] x86/vvmx: virtualize x2APIC mode and APIC accesses can't both be enabled

[Jan Beulich <jbeulich@xxxxxxxx>]

On 24.12.2019 16:32, Roger Pau Monne wrote:
> According to the Intel SDM, "virtualize x2APIC mode" and "virtualize
> APIC accesses" can't be enabled at the same time, or else a
> vm{launch/entry} failure will happen. This was seen when running Xen
> nested and with x2APIC enabled:
> 
> Dec 23 20:06:54.444025 (XEN) d3v0 VMLAUNCH error: 0x7
> [...]
> Dec 23 20:08:33.004078 (XEN) *** Control State ***
> Dec 23 20:08:33.004086 (XEN) PinBased=0000003f CPUBased=b6a075fe 
> SecondaryExec=000014fb
> [...]
> 
> Fix this by making sure nvmx_update_secondary_exec_control clears the
> incompatible bits from the host vmcs before merging it with the nested
> vmcs.
> 
> This fixes a regression reported by osstest in the
> test-amd64-amd64-qemuu-nested-intel job.

It would surely have been nice to include a reference to the
offending commit, despite the bug having been latently there
before.

Jan

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