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[91.219.240.20]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493be4540aesm78099605e9.0.2026.07.01.06.40.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Jul 2026 06:40:40 -0700 (PDT) From: Vitaly Kuznetsov To: marcandre.lureau@redhat.com, qemu-devel@nongnu.org Cc: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Paolo Bonzini , Zhao Liu , Pierrick Bouvier Subject: Re: [PATCH] docs/hyperv: fix misleading hv-crash shutdown description In-Reply-To: <20260701122135.3168729-1-marcandre.lureau@redhat.com> References: <20260701122135.3168729-1-marcandre.lureau@redhat.com> Date: Wed, 01 Jul 2026 15:40:39 +0200 Message-ID: <87pl16hlpk.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.129.124; envelope-from=vkuznets@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, 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 marcandre.lureau@redhat.com writes: > From: Marc-Andr=C3=A9 Lureau > > 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=3D...), which defaults to shutdown. Indeed, > > Signed-off-by: Marc-Andr=C3=A9 Lureau > --- > 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 1c1de77feb6..e1babffb0f9 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 caus= es guest > - to shutdown. This effectively blocks crash dump generation by Windows. > + Note: unlike under genuine Hyper-V, write to HV_X64_MSR_CRASH_CTL trig= gers > + ``qemu_system_guest_panicked()`` via ``KVM_SYSTEM_EVENT_CRASH`` and the > + resulting action depends on the ``-action panic=3D...`` policy (defaul= t: > + ``shutdown``). With the default action, this effectively blocks crash = dump > + generation by Windows. >=20=20 > ``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 suppos= ed 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 featu= re > - effectively prevents Windows from creating dumps upon crashes. > + QAPI by higher levels of the virtualization stack. With the default > + ``-action panic=3Dshutdown`` 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 overco= mmited Reviewed-by: Vitaly Kuznetsov Thanks! --=20 Vitaly