docs/hyperv: fix misleading hv-crash shutdown description
The documentation stated that writing to HV_X64_MSR_CRASH_CTL unconditionally causes the guest to shutdown. In reality, it triggers qemu_system_guest_panicked() via KVM_SYSTEM_EVENT_CRASH and the resulting action depends on the generic panic action policy (-action panic=...), which defaults to shutdown. Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-ID: <20260701122135.3168729-1-marcandre.lureau@redhat.com>
Marc-André Lureau committed
Jul 1, 2026 at 16:21 UTC
521500bd803b3c2c619e52ce423ed039e91310f7
1 file changed
+8
-4
docs/system/i386/hyperv.rst
+8
-4
@@ -71,8 +71,11 @@ Existing enlightenments
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by the guest when it crashes, HV_X64_MSR_CRASH_P0..HV_X64_MSR_CRASH_P5 MSRs
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contain additional crash information. This information is outputted in QEMU log
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and through QAPI.
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- Note: unlike under genuine Hyper-V, write to HV_X64_MSR_CRASH_CTL causes guest
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- to shutdown. This effectively blocks crash dump generation by Windows.
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+ Note: unlike under genuine Hyper-V, write to HV_X64_MSR_CRASH_CTL triggers
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+ ``qemu_system_guest_panicked()`` via ``KVM_SYSTEM_EVENT_CRASH`` and the
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+ resulting action depends on the ``-action panic=...`` policy (default:
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+ ``shutdown``). With the default action, this effectively blocks crash dump
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+ generation by Windows.
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``hv-time``
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Enables two Hyper-V-specific clocksources available to the guest: MSR-based
@@ -304,8 +307,9 @@ currently implemented Hyper-V enlightenments with the following exceptions:
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``hv-version-id-snumber`` can be left unchanged, guests are not supposed to
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behave differently when different Hyper-V version is presented to them.
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- ``hv-crash`` must only be enabled if the crash information is consumed via
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- QAPI by higher levels of the virtualization stack. Enabling this feature
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- effectively prevents Windows from creating dumps upon crashes.
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+ QAPI by higher levels of the virtualization stack. With the default
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+ ``-action panic=shutdown`` policy, enabling this feature effectively
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+ prevents Windows from creating dumps upon crashes.
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- ``hv-reenlightenment`` can only be used on hardware which supports TSC
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scaling or when guest migration is not needed.
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- ``hv-spinlocks`` should be set to e.g. 0xfff when host CPUs are overcommited