whpx: i386: documentation update
Signed-off-by: Mohamed Mediouni <mohamed@unpredictable.fr> Link: https://lore.kernel.org/r/20260422214225.2242-38-mohamed@unpredictable.fr Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Mohamed Mediouni committed
Apr 22, 2026 at 23:42 UTC
f0eb0ef4d83068fc3d909a0266832c7c5fbccb7a
1 file changed
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docs/system/whpx.rst
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@@ -63,7 +63,7 @@ additional functionality compared to ``-device ramfb``, but is
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incompatible with Windows's UEFI GOP implementation, which
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expects a linear framebuffer to be available.
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-Some tracing options
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+Accelerator options
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--------------------
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x86_64
@@ -75,6 +75,11 @@ to undocumented MSRs.
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``-d invalid_mem`` allows to trace accesses to unmapped
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GPAs.
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+``-accel whpx,ssd=off`` disables the separate security domain feature,
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+as in a BTB flush when entering/exiting the guest. This results in a
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+significant MMIO performance increase at the detriment of security
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+mitigations.
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+
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Known issues on x86_64
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----------------------
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@@ -96,45 +101,22 @@ MMX, SSE or AVX instructions for access to MMIO memory ranges.
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Attempts to run such guests will result in an ``Unimplemented handler``
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warning for MMX and a failure to decode for newer instructions.
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-``-M isapc``
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-^^^^^^^^^^^^
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-
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-``-M isapc`` doesn't disable the Hyper-V LAPIC on its own yet. To
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-be able to use that machine, use ``-accel whpx,hyperv=off,kernel-irqchip=off``.
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-
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-However, in QEMU 11.0, the guest will still be a 64-bit x86
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-ISA machine with all the corresponding CPUID leaves exposed.
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-
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-gdbstub
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-^^^^^^^
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-
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-As save/restore of xsave state is not currently present, state
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-exposed through GDB will be incomplete.
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-
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-The same also applies to ``info registers``.
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-
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-``-cpu type`` ignored
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-^^^^^^^^^^^^^^^^^^^^^
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-
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-In this release, -cpu is an ignored argument.
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-
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PIC interrupts on Windows 10
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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On Windows 10, a legacy PIC interrupt injected does not wake the guest
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from an HLT when using the Hyper-V provided interrupt controller.
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-This has been addressed in QEMU 11.0 on Windows 11 platforms but
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-functionality to make it available on Windows 10 isn't present.
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+As such, on Windows 10, using the Hyper-V interrupt controller is
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+disabled by default. You can enable it via ``-M q35,pic=off`` which
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+disables the PIC. In that configuration, using a UEFI is recommended.
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-Workaround: for affected use cases, use ``-M kernel-irqchip=off``.
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+On this release, ``-M kernel-irqchip=`` is not expected to be manually
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+set during normal operation. It remains as a debugging option.
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Known issues on Windows 11
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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-Nested virtualisation-specific Hyper-V enlightenments are not
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-currently exposed.
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-
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arm64
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-----
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