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| author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2024-09-17 18:00:49 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2024-10-17 12:30:21 +0200 |
| commit | 7d7b9c7655a26e09c800ef40373078a80e90d9f3 (patch) | |
| tree | d0892d79e8633f89372df05410a51105f904a233 /docs/system | |
| parent | bbf3810f2c4f97bd7a1982d3e0ff0f00295b8169 (diff) | |
| download | focaccia-qemu-7d7b9c7655a26e09c800ef40373078a80e90d9f3.tar.gz focaccia-qemu-7d7b9c7655a26e09c800ef40373078a80e90d9f3.zip | |
target/i386: Exclude 'hv-syndbg' from 'hv-passthrough'
Windows with Hyper-V role enabled doesn't boot with 'hv-passthrough' when no debugger is configured, this significantly limits the usefulness of the feature as there's no support for subtracting Hyper-V features from CPU flags at this moment (e.g. "-cpu host,hv-passthrough,-hv-syndbg" does not work). While this is also theoretically fixable, 'hv-syndbg' is likely very special and unneeded in the default set. Genuine Hyper-V doesn't seem to enable it either. Introduce 'skip_passthrough' flag to 'kvm_hyperv_properties' and use it as one-off to skip 'hv-syndbg' when enabling features in 'hv-passthrough' mode. Note, "-cpu host,hv-passthrough,hv-syndbg" can still be used if needed. As both 'hv-passthrough' and 'hv-syndbg' are debug features, the change should not have any effect on production environments. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Link: https://lore.kernel.org/r/20240917160051.2637594-3-vkuznets@redhat.com Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'docs/system')
| -rw-r--r-- | docs/system/i386/hyperv.rst | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/docs/system/i386/hyperv.rst b/docs/system/i386/hyperv.rst index 2505dc4c86..009947e391 100644 --- a/docs/system/i386/hyperv.rst +++ b/docs/system/i386/hyperv.rst @@ -262,14 +262,19 @@ Supplementary features ``hv-passthrough`` In some cases (e.g. during development) it may make sense to use QEMU in 'pass-through' mode and give Windows guests all enlightenments currently - supported by KVM. This pass-through mode is enabled by "hv-passthrough" CPU - flag. + supported by KVM. Note: ``hv-passthrough`` flag only enables enlightenments which are known to QEMU (have corresponding 'hv-' flag) and copies ``hv-spinlocks`` and ``hv-vendor-id`` values from KVM to QEMU. ``hv-passthrough`` overrides all other 'hv-' settings on - the command line. Also, enabling this flag effectively prevents migration as the - list of enabled enlightenments may differ between target and destination hosts. + the command line. + + Note: ``hv-passthrough`` does not enable ``hv-syndbg`` which can prevent certain + Windows guests from booting when used without proper configuration. If needed, + ``hv-syndbg`` can be enabled additionally. + + Note: ``hv-passthrough`` effectively prevents migration as the list of enabled + enlightenments may differ between target and destination hosts. ``hv-enforce-cpuid`` By default, KVM allows the guest to use all currently supported Hyper-V |