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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id f10-20020a0560001b0a00b0020402c09067sm14557530wrz.50.2022.04.06.10.36.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Apr 2022 10:36:43 -0700 (PDT) Date: Wed, 6 Apr 2022 18:36:41 +0100 From: "Dr. David Alan Gilbert" To: Igor Mammedov Subject: Re: [PATCH] acpi: Bodge acpi_index migration Message-ID: References: <20220406083531.10217-1-dgilbert@redhat.com> <20220406113446.73ab4e1b@redhat.com> <20220406175939.39d9a277@redhat.com> <20220406185256.084330d5@redhat.com> MIME-Version: 1.0 In-Reply-To: <20220406185256.084330d5@redhat.com> User-Agent: Mutt/2.1.5 (2021-12-30) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, quintela@redhat.com, mst@redhat.com, qemu-devel@nongnu.org, peterx@redhat.com, alex.williamson@redhat.com, leobras@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Igor Mammedov (imammedo@redhat.com) wrote: > On Wed, 6 Apr 2022 17:11:09 +0100 > "Dr. David Alan Gilbert" wrote: > > > * Igor Mammedov (imammedo@redhat.com) wrote: > > > On Wed, 6 Apr 2022 10:38:51 +0100 > > > "Dr. David Alan Gilbert" wrote: > > > > > > > * Igor Mammedov (imammedo@redhat.com) wrote: > > > > > On Wed, 6 Apr 2022 09:35:31 +0100 > > > > > "Dr. David Alan Gilbert (git)" wrote: > > > > > > > > > > > From: "Dr. David Alan Gilbert" > > > > > > > > > > > > The 'acpi_index' field is a statically configured field, which for > > > > > > some reason is migrated; this never makes much sense because it's > > > > > > command line static. > > > > > > > > > > that's true only for the field that's part of PCIDEvice, > > > > > however AcpiPciHpState::acpi_index is runtime state and _must_ > > > > > be migrated if set, otherwise guest might get wrong index > > > > > if it's in process of querying it > > > > > > > > So this patch only changes the piix4.c version; I'm confused, is there > > > > a AcpiPciHpState::acpi_index that's runtime setable in there? > > > > > > > > > VMSTATE_PCI_HOTPLUG(acpi_pci_hotplug, PIIX4PMState, > > > ^^^ AcpiPciHpState > > > > > > vmstate_test_use_acpi_hotplug_bridge, > > > > > > - vmstate_acpi_pcihp_use_acpi_index), > > > > > > hw/acpi/pcihp.c:pci_write(): > > > s->acpi_index = object_property_get_uint(o, "acpi-index", NULL); > > > > > > s->acpi_index is runtime value that is supposed to be migrated if it's set > > > to something other then 0 > > > > > > I may have botched VMSTATE_PCI_HOTPLUG, intent was to migrate > > > AcpiPciHpState::acpi_index if necessary. But I'm not sure how > > > if I used correct approach for to migrate an optional value > > > i.e. maybe instead of VMSTATE_UINT32_TEST(pcihp.acpi_index, state, test_acpi_index) > > > I should've used subsection, because destination has no clue if > > > acpi_index would be transmitted over wire or not? > > > > > > > > > However, on piix4 it's conditional, and the condition/test function > > > > > > ends up having the wrong pointer passed to it (it gets a PIIX4PMState > > > > > > not the AcpiPciHpState it was expecting, because VMSTATE_PCI_HOTPLUG > > > > > > is a macro and not another struct). This means the field is randomly > > > > > > loaded/saved based on a random pointer. In 6.x this random pointer > > > > > > randomly seems to get 0 for everyone (!); in 7.0rc it's getting junk > > > > > > and trying to load a field that the source didn't send. The migration > > > > > > stream gets out of line and hits the section footer. > > > > > > > > > > I'm a bit confused by description, > > > > > do you have a reproducer for me to try? > > > > > > > > Yeh, see the linked gitlab case command line: > > > > https://gitlab.com/qemu-project/qemu/-/issues/932 > > > > > > > > ./x86_64-softmmu/qemu-system-x86_64 -M pc-q35-6.2 -m 512 -device virtio-scsi-pci,id=scsihw0,bus=pcie.0,addr=0x5,acpi-index=3 -drive if=none,my.qcow2,format=qcow2,id=drive-scsi0,node-name=scsi0 -device 'scsi-hd,bus=scsihw0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0,id=scsi0' -nographic > > > > > > > > just migrating from a 6.2 to a head triggers this. > > > > > > Over here any migration from qemu-6.2 to HEAD at 3d31fe4d662f13c7 > > > fails even without acpi-index, as simple as this: > > > > > > qemu-system-x86_64-6.2 -M pc-i440fx-6.2 -m 512 -vnc :0 -monitor stdio > > > (qemu) stop > > > (qemu) migrate "exec:gzip -c > STATEFILE.gz" > > > > > > qemu-system-x86_64-7.0 -M pc-i440fx-6.2 -m 512 -vnc :0 -monitor stdio -incoming "exec: gzip -c -d STATEFILE.gz" > > > > > > (qemu) qemu-system-x86_64-7.0: Missing section footer for 0000:00:01.3/piix4_pm > > > qemu-system-x86_64-7.0: load of migration failed: Invalid argument > > > > > > > > > Like you pointed out in gitlab issue, vmstate_acpi_pcihp_use_acpi_index > > > is broken. Following applied to HEAD should fix immediate issue on destination > > > reading random value: > > > > > > diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c > > > index f0b5fac44a..c97db491c8 100644 > > > --- a/hw/acpi/piix4.c > > > +++ b/hw/acpi/piix4.c > > > @@ -269,6 +269,11 @@ static bool piix4_vmstate_need_smbus(void *opaque, int version_id) > > > return pm_smbus_vmstate_needed(); > > > } > > > > > > +static bool vmstate_piix4_need_acpi_index(void *opaque, int version_id) > > > +{ > > > + PIIX4PMState *s = PIIX4_PM(opaque); > > > + return vmstate_acpi_pcihp_use_acpi_index(&(s->acpi_pci_hotplug), version_id); > > > +} > > > > But if acpi_index was set on the source 6.2 host, it won't send the > > index, but the 7.0 would expect it, and it would fail in the same way > > wouldn't it? > > With piix4 fixed up 7.0 won't expect field as s->acpi_index initialized to 0 > so check will always return 0 and the field won't be expected. > ( testing confirms it). > If test on 6.2 host somehow manages to return 1, destination won't > be able to accept it, because it has no idea about it (that is not fixable, I'm afraid). > > For Q35 we set check to NULL > VMSTATE_PCI_HOTPLUG(acpi_pci_hotplug, > ICH9LPCPMRegs, > NULL, NULL), > > which if I read vmstate_load_state() correctly will always expect > the field and will always store fields since field->version_id == 0 > for VMSTATE_UINT32_TEST. > > So we can't remove field without breaking Q35. Yes. > Net effect: > * not send the field for PC machine (ever) > * send field always for Q35 (always) > > So your patch is good with fixed commit message > and a comment close to the field that it's not really used with piix4 Could you write a new commit message based on mine? > And to make migration of acpi_index on PC machine working, > we need add an extra subsection that should be able to > handle conditional value. Yes; I hadn't realised acpi_index was actually writeable. Dave > > > > > Dave > > > > > /* qemu-kvm 1.2 uses version 3 but advertised as 2 > > > * To support incoming qemu-kvm 1.2 migration, change version_id > > > * and minimum_version_id to 2 below (which breaks migration from > > > @@ -299,7 +304,7 @@ static const VMStateDescription vmstate_acpi = { > > > struct AcpiPciHpPciStatus), > > > VMSTATE_PCI_HOTPLUG(acpi_pci_hotplug, PIIX4PMState, > > > vmstate_test_use_acpi_hotplug_bridge, > > > - vmstate_acpi_pcihp_use_acpi_index), > > > + vmstate_piix4_need_acpi_index), > > > VMSTATE_END_OF_LIST() > > > }, > > > .subsections = (const VMStateDescription*[]) { > > > > > > > > > > Dave > > > > > > > > > > The bodge is on piix4 never to load the field: > > > > > > a) Most 6.x builds never send it, so most of the time the migration > > > > > > will work. > > > > > > b) We can backport this fix to 6.x to remove the boobytrap. > > > > > > c) It should never have made a difference anyway since the acpi-index > > > > > > is command line configured and should be correct on the destination > > > > > > anyway > > > > > > d) ich9 is still sending/receiving this (unconditionally all the time) > > > > > > but due to (c) should never notice. We could follow up to make it > > > > > > skip. > > > > > > > > > > > > It worries me just when (a) actually happens. > > > > > > > > > > > > Fixes: b32bd76 ("pci: introduce acpi-index property for PCI device") > > > > > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/932 > > > > > > > > > > > > Signed-off-by: Dr. David Alan Gilbert > > > > > > --- > > > > > > hw/acpi/acpi-pci-hotplug-stub.c | 4 ---- > > > > > > hw/acpi/pcihp.c | 6 ------ > > > > > > hw/acpi/piix4.c | 11 ++++++++++- > > > > > > include/hw/acpi/pcihp.h | 2 -- > > > > > > 4 files changed, 10 insertions(+), 13 deletions(-) > > > > > > > > > > > > diff --git a/hw/acpi/acpi-pci-hotplug-stub.c b/hw/acpi/acpi-pci-hotplug-stub.c > > > > > > index 734e4c5986..a43f6dafc9 100644 > > > > > > --- a/hw/acpi/acpi-pci-hotplug-stub.c > > > > > > +++ b/hw/acpi/acpi-pci-hotplug-stub.c > > > > > > @@ -41,7 +41,3 @@ void acpi_pcihp_reset(AcpiPciHpState *s, bool acpihp_root_off) > > > > > > return; > > > > > > } > > > > > > > > > > > > -bool vmstate_acpi_pcihp_use_acpi_index(void *opaque, int version_id) > > > > > > -{ > > > > > > - return false; > > > > > > -} > > > > > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > > > > > > index 6351bd3424..bf65bbea49 100644 > > > > > > --- a/hw/acpi/pcihp.c > > > > > > +++ b/hw/acpi/pcihp.c > > > > > > @@ -554,12 +554,6 @@ void acpi_pcihp_init(Object *owner, AcpiPciHpState *s, PCIBus *root_bus, > > > > > > OBJ_PROP_FLAG_READ); > > > > > > } > > > > > > > > > > > > -bool vmstate_acpi_pcihp_use_acpi_index(void *opaque, int version_id) > > > > > > -{ > > > > > > - AcpiPciHpState *s = opaque; > > > > > > - return s->acpi_index; > > > > > > -} > > > > > > - > > > > > > const VMStateDescription vmstate_acpi_pcihp_pci_status = { > > > > > > .name = "acpi_pcihp_pci_status", > > > > > > .version_id = 1, > > > > > > diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c > > > > > > index cc37fa3416..48aeedd5f0 100644 > > > > > > --- a/hw/acpi/piix4.c > > > > > > +++ b/hw/acpi/piix4.c > > > > > > @@ -267,6 +267,15 @@ static bool piix4_vmstate_need_smbus(void *opaque, int version_id) > > > > > > return pm_smbus_vmstate_needed(); > > > > > > } > > > > > > > > > > > > +/* > > > > > > + * This is a fudge to turn off the acpi_index field, whose > > > > > > + * test was always broken on piix4. > > > > > > + */ > > > > > > +static bool vmstate_test_never(void *opaque, int version_id) > > > > > > +{ > > > > > > + return false; > > > > > > +} > > > > > > + > > > > > > /* qemu-kvm 1.2 uses version 3 but advertised as 2 > > > > > > * To support incoming qemu-kvm 1.2 migration, change version_id > > > > > > * and minimum_version_id to 2 below (which breaks migration from > > > > > > @@ -297,7 +306,7 @@ static const VMStateDescription vmstate_acpi = { > > > > > > struct AcpiPciHpPciStatus), > > > > > > VMSTATE_PCI_HOTPLUG(acpi_pci_hotplug, PIIX4PMState, > > > > > > vmstate_test_use_acpi_hotplug_bridge, > > > > > > - vmstate_acpi_pcihp_use_acpi_index), > > > > > > + vmstate_test_never), > > > > > > VMSTATE_END_OF_LIST() > > > > > > }, > > > > > > .subsections = (const VMStateDescription*[]) { > > > > > > diff --git a/include/hw/acpi/pcihp.h b/include/hw/acpi/pcihp.h > > > > > > index af1a169fc3..7e268c2c9c 100644 > > > > > > --- a/include/hw/acpi/pcihp.h > > > > > > +++ b/include/hw/acpi/pcihp.h > > > > > > @@ -73,8 +73,6 @@ void acpi_pcihp_reset(AcpiPciHpState *s, bool acpihp_root_off); > > > > > > > > > > > > extern const VMStateDescription vmstate_acpi_pcihp_pci_status; > > > > > > > > > > > > -bool vmstate_acpi_pcihp_use_acpi_index(void *opaque, int version_id); > > > > > > - > > > > > > #define VMSTATE_PCI_HOTPLUG(pcihp, state, test_pcihp, test_acpi_index) \ > > > > > > VMSTATE_UINT32_TEST(pcihp.hotplug_select, state, \ > > > > > > test_pcihp), \ > > > > > > > > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK