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Tue, 05 Apr 2022 14:02:44 -0700 (PDT) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id y12-20020a056602164c00b00645cdfb42dasm9444002iow.30.2022.04.05.14.02.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Apr 2022 14:02:44 -0700 (PDT) Date: Tue, 5 Apr 2022 15:02:42 -0600 From: Alex Williamson To: "Dr. David Alan Gilbert (git)" Subject: Re: [PATCH] acpi: Bodge acpi_index migration Message-ID: <20220405150242.517e9bdb.alex.williamson@redhat.com> In-Reply-To: <20220405190658.65187-1-dgilbert@redhat.com> References: <20220405190658.65187-1-dgilbert@redhat.com> Organization: Red Hat MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=alex.williamson@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=alex.williamson@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_H5=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, leobras@redhat.com, imammedo@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 5 Apr 2022 20:06:58 +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. > > 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. FWIW, after some hunting and pecking, 6.2 (64bit): (gdb) p &((struct AcpiPciHpState *)0)->acpi_index $1 = (uint32_t *) 0xc04 (gdb) p &((struct PIIX4PMState *)0)->ar.tmr.io.addr $2 = (hwaddr *) 0xc00 f53faa70bb63: (gdb) p &((struct AcpiPciHpState *)0)->acpi_index $1 = (uint32_t *) 0xc04 (gdb) p &((struct PIIX4PMState *)0)->io_gpe.coalesced.tqh_circ.tql_prev $2 = (struct QTailQLink **) 0xc00 So yeah, it seems 0xc04 will always be part of a pointer on current mainline. I can't really speak to the ACPIPMTimer MemoryRegion in the PIIX4PMState, maybe if there's a hwaddr it's always 32bit and the upper dword is reliably zero? Thanks, Alex > The migration > stream gets out of line and hits the section footer. > > 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), \