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Mon, 27 Jul 2026 11:52:16 +0000 (UTC) Received: from localhost (unknown [10.44.24.5]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B751D30010C8; Mon, 27 Jul 2026 11:52:15 +0000 (UTC) From: =?utf-8?q?Marc-Andr=C3=A9_Lureau?= Date: Mon, 27 Jul 2026 15:51:17 +0400 Subject: [GIT PULL 08/23] docs/hyperv: fix misleading hv-crash shutdown description MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Message-Id: <20260727-fix-v1-8-ca3fa3851347@redhat.com> References: <20260727-fix-v1-0-ca3fa3851347@redhat.com> In-Reply-To: <20260727-fix-v1-0-ca3fa3851347@redhat.com> To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , Paolo Bonzini , Zhao Liu , Pierrick Bouvier X-Developer-Signature: v=1; a=openpgp-sha256; l=2505; i=marcandre.lureau@redhat.com; h=from:subject:message-id; bh=37ToipwIaXpMMjvpg8YSWf1licth1SjqGNKBZN8+5bE=; b=owEBbAKT/ZANAwAKAdro4Ql1lpzlAcsmYgBqZ0Y/pYW0pTY+5t39HHKRU2Hc46khOktK7TOrX 0ZI4coFs2CJAjIEAAEKAB0WIQSHqb2TP4fGBtJ29i3a6OEJdZac5QUCamdGPwAKCRDa6OEJdZac 5a8mD/MFIxGGXiFJTJzQ1r+YnfZXNk+pVyevsckdw1eOMUce84rMwC0+LOHxwZcQfZIA2uQxBzx kCxMnOzww2NJ6VRKXSV+TIQA7j/LVAKyEvV9nrHIlL+YPhV+wt5BZRaHJrbp8/5tmxYiIxdaDTO cegqOK/XX1LA9LFJuaXXbIER3GJvCYpUi/zVD95DfuzdqfZ8OdLblwUcJHvP3Yqn3skDOw9UTuD EoRLF88O5tgZ4S3pBC/kYfhObHfQZTBsNYEEsCsItAmPkY0JsUS1P0tgY0mcLW0QIxSMSX89HfR ygZo4Aca3nZ+vdLksjHqwHo47R+q6gZnW/Orm4twkp5B1Osc4TA4ydZxCKrET3vkiA7tic5r4JQ Vomhb1bbYHrkFAxGm59y+IokEvLUMnyInemfapm3rLke5oMigkYdbJ6s80PLCi4GTmryO5cjXJa gx27KxwP/YJJk/DW2B5RmZUIsK0c0O5po7MKxX5fWKrsOSzRWqvl57tTNYIGWzQ5oOvLTvmfWGX AgbLVuDXZTnYVvrcn/vOmtQW225XIa4CkT8bcaF/YEbOMC9rQYg26Qcs1msMVOBsQcXjrZBlIeQ 4uBQB140ub1A2Rhrn+nKIuE3aDFFxtu5SFmYTT+jFMKoIgsQvpmtmDWDQ3wVhlCWJdTDpPQTpx/ uBSKwC+pQDh7e X-Developer-Key: i=marcandre.lureau@redhat.com; a=openpgp; fpr=87A9BD933F87C606D276F62DDAE8E10975969CE5 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=marcandre.lureau@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -36 X-Spam_score: -3.7 X-Spam_bar: --- X-Spam_report: (-3.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.58, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org 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 Signed-off-by: Marc-André Lureau Message-ID: <20260701122135.3168729-1-marcandre.lureau@redhat.com> --- docs/system/i386/hyperv.rst | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/docs/system/i386/hyperv.rst b/docs/system/i386/hyperv.rst index 1c1de77feb65..e1babffb0f99 100644 --- a/docs/system/i386/hyperv.rst +++ b/docs/system/i386/hyperv.rst @@ -71,8 +71,11 @@ Existing enlightenments by the guest when it crashes, HV_X64_MSR_CRASH_P0..HV_X64_MSR_CRASH_P5 MSRs contain additional crash information. This information is outputted in QEMU log and through QAPI. - Note: unlike under genuine Hyper-V, write to HV_X64_MSR_CRASH_CTL causes guest - to shutdown. This effectively blocks crash dump generation by Windows. + Note: unlike under genuine Hyper-V, write to HV_X64_MSR_CRASH_CTL triggers + ``qemu_system_guest_panicked()`` via ``KVM_SYSTEM_EVENT_CRASH`` and the + resulting action depends on the ``-action panic=...`` policy (default: + ``shutdown``). With the default action, this effectively blocks crash dump + generation by Windows. ``hv-time`` 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: ``hv-version-id-snumber`` can be left unchanged, guests are not supposed to behave differently when different Hyper-V version is presented to them. - ``hv-crash`` must only be enabled if the crash information is consumed via - QAPI by higher levels of the virtualization stack. Enabling this feature - effectively prevents Windows from creating dumps upon crashes. + QAPI by higher levels of the virtualization stack. With the default + ``-action panic=shutdown`` policy, enabling this feature effectively + prevents Windows from creating dumps upon crashes. - ``hv-reenlightenment`` can only be used on hardware which supports TSC scaling or when guest migration is not needed. - ``hv-spinlocks`` should be set to e.g. 0xfff when host CPUs are overcommited -- 2.55.0