Messages in this thread | | | Subject | Re: commit 3c2e7f7de3 (KVM use NPT page attributes) causes boot failures | From | Xiao Guangrong <> | Date | Wed, 2 Sep 2015 18:57:15 +0800 |
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On 09/02/2015 06:54 PM, Markus Trippelsdorf wrote: > On 2015.09.02 at 18:27 +0800, Xiao Guangrong wrote: >> >> >> On 09/02/2015 05:38 PM, Markus Trippelsdorf wrote: >>> 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. >> >> So the PAT is the value after CPU reset, it's likely PAT is not initialized on >> the local CPU. > > Could it be a simple AMD/INTEL difference. I'm running a AMD CPU and I > see many !use_intel() in if statements in arch/x86/kernel/cpu/mtrr/main.c... >
#define use_intel() (mtrr_if && mtrr_if->use_intel_if == 1)
And i checked your CPU supports "mtrr" /proc/info, so it should use generic_mtrr_ops and generic_mtrr_ops.use_intel_if = 1. That means AMD CPU also use "intel" way. :)
Please refer to the initiation of "mtrr_if" in mtrr_bp_init().
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