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https://ovirt-jira.atlassian.net/browse/OVIRT-2545?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Eyal Edri reassigned OVIRT-2545:
--------------------------------
Assignee: Marc Dequènes (Duck) (was: infra)
Hi Duck,
Can you check if this is still needed?
> Fwd: [ovirt-users] Backport KVM bug fix for nested KVM in ESXi and Hyper-V
> --------------------------------------------------------------------------
>
> Key: OVIRT-2545
> URL: https://ovirt-jira.atlassian.net/browse/OVIRT-2545
> Project: oVirt - virtualization made easy
> Issue Type: By-EMAIL
> Reporter: sbonazzo
> Assignee: Marc Dequènes (Duck)
>
> Opening a ticket because looks like the forwarded email doesn't show up on
> list archives at
> https://lists.ovirt.org/archives/list/[email protected]/2018/10/
> Marc can you please check?
> ---------- Forwarded message ---------
> From: Gianluca Cecchi <[email protected]>
> Date: mar 16 ott 2018 alle ore 12:57
> Subject: [ovirt-users] Backport KVM bug fix for nested KVM in ESXi and
> Hyper-V
> To: users <[email protected]>
> Hello,
> I send a dedicated subject message on this topic.
> Also, the reply to my other related message seems not visible inside list
> archive page for some reason.
> It seems this nasty problem in nested virt using pc-i440fx-rhel7.X.0
> machine type with X >= 3 impacts not only vSphere as main hypervisor for
> nested KVM, but other hypervisors too (Hyper-V) and other machine types too
> and could be due to a bug in KVM, so in the kernel, if I understood
> correctly.
> According to this link below
> https://bugs.launchpad.net/qemu/+bug/1636217
> and its comment by Roman Kagan in June this year:
> "
> This is a KVM bug. It has been fixed in mainstream Linux in
> commit d391f1207067268261add0485f0f34503539c5b0
> Author: Vitaly Kuznetsov <email address hidden>
> Date: Thu Jan 25 16:37:07 2018 +0100
> x86/kvm/vmx: do not use vm-exit instruction length for fast MMIO when
> running nested
> I was investigating an issue with seabios >= 1.10 which stopped working
> for nested KVM on Hyper-V. The problem appears to be in
> handle_ept_violation() function: when we do fast mmio we need to skip
> the instruction so we do kvm_skip_emulated_instruction(). This, however,
> depends on VM_EXIT_INSTRUCTION_LEN field being set correctly in VMCS.
> However, this is not the case.
> Intel's manual doesn't mandate VM_EXIT_INSTRUCTION_LEN to be set when
> EPT MISCONFIG occurs. While on real hardware it was observed to be set,
> some hypervisors follow the spec and don't set it; we end up advancing
> IP with some random value.
> I checked with Microsoft and they confirmed they don't fill
> VM_EXIT_INSTRUCTION_LEN on EPT MISCONFIG.
> Fix the issue by doing instruction skip through emulator when running
> nested.
> Fixes: 68c3b4d1676d870f0453c31d5a52e7e65c7448ae
> Suggested-by: Radim Krčmář <email address hidden>
> Suggested-by: Paolo Bonzini <email address hidden>
> Signed-off-by: Vitaly Kuznetsov <email address hidden>
> Acked-by: Michael S. Tsirkin <email address hidden>
> Signed-off-by: Radim Krčmář <email address hidden>
> Although the commit mentions Hyper-V as L0 hypervisor, the same problem
> pertains to ESXi.
> The commit is included in v4.16.
> "
> Is it possible to backport the fix to the kernel provided by plain
> RHEL/CentOS hosts and/or RHVH/ovirt-ng nodes?
> Thanks,
> Gianluca
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> --
> SANDRO BONAZZOLA
> MANAGER, SOFTWARE ENGINEERING, EMEA R&D RHV
> Red Hat EMEA <https://www.redhat.com/>
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