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

Xiao Guangrong
2015-09-01T22:37:25Z

On 09/01/2015 09:56 PM, Markus Trippelsdorf wrote:
> On 2015.09.01 at 21:00 +0800, Xiao Guangrong wrote:
>>
>> Did it trigger the BUG()/BUG_ON() in mtrr2protval()/fallback_mtrr_type()?
>> If yes, could you please print the actual value out?
>
> It is the BUG() in fallback_mtrr_type(). I changed it to a printk and
> it prints 1 for the value of mtrr.
>
> MTRR_TYPE_WRCOMB 1
>

Then I suspect pat is not enabled in your box, could you please check
CONFIG_X86_PAT is selected in your .config file, pat is shown in
/proc/cpuid, "nopat" kernel parameter is used, and dmesg | grep PAT.

I will post a fix if the suspect is right.