Re: commit 3c2e7f7de3 (KVM use NPT page attributes) causes boot failures

Markus Trippelsdorf
2015-09-02T09:38:25Z

On 2015.09.02 at 17:17 +0800, Xiao Guangrong wrote:
> >
> > No. PAT is of course enabled and booting is successful sometimes even
> > with the BUG() in allback_mtrr_type(). I suspect a setup (timing) issue.
>
> Thanks for your confirmation.
>
> >
> > markus@x4 linux % cat .config | grep X86_PAT
> > CONFIG_X86_PAT=y
> > markus@x4 linux % dmesg | grep PAT
> > [ 0.000000] x86/PAT: Configuration [0-7]: WB WC UC- UC WB WC UC- WT
>
> Strange, BP processor has already set WC to PAT1, however KVM does not read it out
> from PAT MSR on its local CPU.
>
> Hmm... PAT default values do not include WC, it seems initing PAT on SP has not
> finished after module_init()?
>
> Could please apply this diff and test it again?

(Your patch was malformed.)

[ 2.138098] kvm: Nested Virtualization enabled
[ 2.138153] kvm: Nested Paging enabled
[ 2.138204] KVM PAT: 0x7040600070406.
[ 2.138255] mtrr2protval[0]:18.
[ 2.138306] mtrr2protval[1]:ff.
[ 2.138356] mtrr2protval[2]:0.
[ 2.138408] mtrr2protval[3]:0.
[ 2.138459] mtrr2protval[4]:8.
[ 2.138510] mtrr2protval[5]:ff.
[ 2.138561] mtrr2protval[6]:0.
[ 2.138612] mtrr2protval[7]:10.
[ 2.138662] BUG in fallback_mtrr_type, mtrr = 1.

--
Markus