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author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2021-11-29 12:47:01 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-03-17 10:45:17 +0300 |
commit | 0ef55bafabb9ebf45bf5cdfaeabdc37d206e7624 (patch) | |
tree | e80dbc508a30168ca223da3052dcf7e2eaffca4a /fs | |
parent | 9da269bee7ead0922dc091475e525cbe21cbdfa8 (diff) | |
download | linux-0ef55bafabb9ebf45bf5cdfaeabdc37d206e7624.tar.xz |
KVM: nVMX: Don't use Enlightened MSR Bitmap for L3
commit 250552b925ce400c17d166422fde9bb215958481 upstream.
When KVM runs as a nested hypervisor on top of Hyper-V it uses Enlightened
VMCS and enables Enlightened MSR Bitmap feature for its L1s and L2s (which
are actually L2s and L3s from Hyper-V's perspective). When MSR bitmap is
updated, KVM has to reset HV_VMX_ENLIGHTENED_CLEAN_FIELD_MSR_BITMAP from
clean fields to make Hyper-V aware of the change. For KVM's L1s, this is
done in vmx_disable_intercept_for_msr()/vmx_enable_intercept_for_msr().
MSR bitmap for L2 is build in nested_vmx_prepare_msr_bitmap() by blending
MSR bitmap for L1 and L1's idea of MSR bitmap for L2. KVM, however, doesn't
check if the resulting bitmap is different and never cleans
HV_VMX_ENLIGHTENED_CLEAN_FIELD_MSR_BITMAP in eVMCS02. This is incorrect and
may result in Hyper-V missing the update.
The issue could've been solved by calling evmcs_touch_msr_bitmap() for
eVMCS02 from nested_vmx_prepare_msr_bitmap() unconditionally but doing so
would not give any performance benefits (compared to not using Enlightened
MSR Bitmap at all). 3-level nesting is also not a very common setup
nowadays.
Don't enable 'Enlightened MSR Bitmap' feature for KVM's L2s (real L3s) for
now.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20211129094704.326635-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alexandru Matei <alexandru.matei@uipath.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
0 files changed, 0 insertions, 0 deletions