https://bugzilla.kernel.org/show_bug.cgi?id=203543 --- Comment #9 from dhill@xxxxxxxxxx --- Hi guys, I justed tested kernel 5.2.1-rc1 which contains the following commit reverting the previously mentionned commit but... the problem is still there: [root@wolfe linux-stable]# su - jenkins -s /bin/bash [jenkins@wolfe ~]$ ssh root@192.168.122.2 Activate the web console with: systemctl enable --now cockpit.socket Last login: Tue May 21 08:53:28 2019 from 192.168.122.1 [root@undercloud-0-rhosp15 ~]# modprobe kvm_intel modprobe: ERROR: could not insert 'kvm_intel': Input/output error [root@undercloud-0-rhosp15 ~]# logout Connection to 192.168.122.2 closed. [jenkins@wolfe ~]$ uname -a Linux wolfe.orion 5.2.0-20190521081919+ #6 SMP Tue May 21 08:25:14 EDT 2019 x86_64 x86_64 x86_64 GNU/Linux I'll try reverting the commit and then reverting only the commit that causes issues. commit f93f7ede087f2edcc18e4b02310df5749a6b5a61 Author: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> Date: Wed May 8 09:08:19 2019 -0700 Revert "KVM: nVMX: Expose RDPMC-exiting only when guest supports PMU" The RDPMC-exiting control is dependent on the existence of the RDPMC instruction itself, i.e. is not tied to the "Architectural Performance Monitoring" feature. For all intents and purposes, the control exists on all CPUs with VMX support since RDPMC also exists on all VCPUs with VMX supported. Per Intel's SDM: The RDPMC instruction was introduced into the IA-32 Architecture in the Pentium Pro processor and the Pentium processor with MMX technology. The earlier Pentium processors have performance-monitoring counters, but they must be read with the RDMSR instruction. Because RDPMC-exiting always exists, KVM requires the control and refuses to load if it's not available. As a result, hiding the PMU from a guest breaks nested virtualization if the guest attemts to use KVM. While it's not explicitly stated in the RDPMC pseudocode, the VM-Exit check for RDPMC-exiting follows standard fault vs. VM-Exit prioritization for privileged instructions, e.g. occurs after the CPL/CR0.PE/CR4.PCE checks, but before the counter referenced in ECX is checked for validity. In other words, the original KVM behavior of injecting a #GP was correct, and the KVM unit test needs to be adjusted accordingly, e.g. eat the #GP when the unit test guest (L3 in this case) executes RDPMC without RDPMC-exiting set in the unit test host (L2). This reverts commit e51bfdb68725dc052d16241ace40ea3140f938aa. Fixes: e51bfdb68725 ("KVM: nVMX: Expose RDPMC-exiting only when guest supports PMU") Reported-by: David Hill <hilld@xxxxxxxxxxxxxxx> Cc: Saar Amar <saaramar@xxxxxxxxxxxxx> Cc: Mihai Carabas <mihai.carabas@xxxxxxxxxx> Cc: Jim Mattson <jmattson@xxxxxxxxxx> Cc: Liran Alon <liran.alon@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> On 2019-05-08 6:14 p.m., bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=203543 > > --- Comment #8 from Liran Alon (liran.alon@xxxxxxxxxx) --- > +Paolo > > What are your thoughts on this? > What is the reason that KVM relies on CPU_BASED_RDPMC_EXITING to be exposed > from underlying CPU? How is it critical for it’s functionality? > If it’s because we want to make sure that we hide host PMCs, we should > condition this to be a min requirement of kvm_intel only in case underlying > CPU > exposes PMU to begin with. > Do you agree? If yes, I can create the patch to fix this. > > -Liran > >> On 8 May 2019, at 16:51, bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: >> >> >> >> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugzilla.kernel.org_show-5Fbug.cgi-3Fid-3D203543&d=DwIDaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=Jk6Q8nNzkQ6LJ6g42qARkg6ryIDGQr-yKXPNGZbpTx0&m=7TirfLMNxYI-3Ygxm3kjDUB49Jwmk8bqD7671wy0hi8&s=Z_L1UqH19zon0ohDrCMU91ixA-Wn_vO7d-fO8s2G3PI&e= >> >> --- Comment #5 from David Hill (hilld@xxxxxxxxxxxxxxx) --- >> I can confirm that reverting that commit solves the problem: >> >> e51bfdb68725 ("KVM: nVMX: Expose RDPMC-exiting only when guest supports >> PMU”) >> >> -- >> You are receiving this mail because: >> You are watching the assignee of the bug. -- You are receiving this mail because: You are watching the assignee of the bug.
