Re: [Qemu-devel] [PATCH] pc: Use "min-[x]level" on compat_props

[Eduardo Habkost]

On Mon, Jun 05, 2017 at 12:56:55PM -0300, Eduardo Habkost wrote:
> Since the automatic cpuid-level code was introduced in commit
> c39c0edf9bb3b968ba95484465a50c7b19f4aa3a, the CPU model tables just
> define the default CPUID level code (set using "min-level").  Setting
> "[x]level" forces CPUID level to a specific value and disable the
> automatic-level logic.
> 
> But the PC compat code was not updated and the existing "[x]level"
> compat properties broke compatibility for people using features that
> triggered the auto-level code.  To keep previous behavior, we should set
> "min-[x]level" instead of "[x]level" on compat_props.
> 
> This was not a problem for most cases, because old machine-types don't
> have full-cpuid-auto-level enabled.  The only common use case it broke
> was the CPUID[7] auto-level code, that was already enabled since the
> first CPUID[7] feature was introduced (in QEMU 1.4.0).
> 
> This causes the regression reported at:
> https://bugzilla.redhat.com/show_bug.cgi?id=1454641
> 
> Change the PC compat code to use "min-[x]level" instead of "[x]level" on
> compat_props, and add new test cases to ensure we don't break this
> again.
> 
> Reported-by: "Guo, Zhiyi" <address@hidden>
> Signd-off-by: Eduardo Habkost <address@hidden>

Signed-off-by: Eduardo Habkost <address@hidden>

-- 
Eduardo