Hi, I'm sure my bisect has nothing to do with KVM, because it was quick shot between -rc1 and previous release. This old CPU doesn't have EPT (see attached file) ./run_tests.sh FAIL apic-split (timeout; duration=90s) FAIL ioapic-split (timeout; duration=90s) FAIL apic (timeout; duration=30) ... ^C few RIP is_tdp_mmu_root observed in dmesg Z. On Tue, 10 Nov 2020 17:13:21 -0800 Ben Gardon <bgardon@xxxxxxxxxx> wrote: > Hi Zdenek, > > That crash is most likely the result of a missing check for an invalid > root HPA or NULL shadow page in is_tdp_mmu_root, which could have > prevented the NULL pointer dereference. > However, I'm not sure how a vCPU got to that point in the page fault > handler with a bad EPT root page. > > I see VMX in your list of flags, is your machine 64 bit with EPT or > some other configuration? > > I'm surprised you are finding your machine unable to boot for > bisecting. Do you know if it's crashing in the same spot or somewhere > else? I wouldn't expect the KVM page fault handler to run as part of > boot. > > I will send out a patch first thing tomorrow morning (PST) to WARN > instead of crashing with a NULL pointer dereference. Are you able to > reproduce the issue with any KVM selftest? > > Ben > > > On Tue, Nov 10, 2020 at 7:24 AM Zdenek Kaspar <zkaspar82@xxxxxxxxx> > wrote: > > > > Hi, > > > > attached file is result from today's linux-master (with fixes > > for 5.10-rc4) when I try to start VM on older machine: > > > > model name : Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz > > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr > > pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe > > syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl > > cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 > > xtpr pdcm lahf_lm pti tpr_shadow dtherm vmx flags : > > tsc_offset vtpr > > > > I did quick check with 5.9 (distro kernel) and it works, > > but VM performance seems extremely impacted. 5.8 works fine. > > > > Back to 5.10 issue: it's problematic since 5.10-rc1 and I have no > > luck with bisecting (machine doesn't boot). > > > > TIA, Z.
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