From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39973) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fb9f1-0007SJ-BF for qemu-devel@nongnu.org; Thu, 05 Jul 2018 15:11:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fb9ey-0005Uw-6f for qemu-devel@nongnu.org; Thu, 05 Jul 2018 15:11:23 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:33314 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fb9ey-0005Ua-05 for qemu-devel@nongnu.org; Thu, 05 Jul 2018 15:11:20 -0400 Date: Thu, 5 Jul 2018 22:11:18 +0300 From: "Michael S. Tsirkin" Message-ID: <20180705220402-mutt-send-email-mst@kernel.org> References: <20180705181148.26871-1-clg@kaod.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20180705181148.26871-1-clg@kaod.org> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] pci: remove pci_del_option_rom() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?iso-8859-1?Q?C=E9dric?= Le Goater Cc: qemu-devel@nongnu.org, Paolo Bonzini , Peter Xu , Alex Williamson , Marcel Apfelbaum On Thu, Jul 05, 2018 at 08:11:48PM +0200, C=E9dric Le Goater wrote: > PCI devices needing a ROM allocate an optional MemoryRegion with > pci_add_option_rom(). pci_del_option_rom() does the cleanup when the > device is destroyed. The only action taken by this routine is to call > vmstate_unregister_ram() which clears the id string of the optional > ROM RAMBlock and now, also flags the RAMBlock as non-migratable. This > was recently added by commit b895de502717 ("migration: discard > non-migratable RAMBlocks"), . >=20 > VFIO devices do their own allocation of the PCI ROM region. It is > initialized in vfio_pci_size_rom() in which the PCI attribute > 'has_rom' is set to true but the RAMBlock of the ROM region is not > allocated. When the associated PCI device is deleted, > pci_del_option_rom() calls vmstate_unregister_ram() which tries to > flag a NULL RAMBlock because 'has_rom' is set, leading to a SEGV . >=20 > The use of vmstate_unregister_ram() in the PCI device was added in > commit b0e56e0b63f350691b52d3e75e89bb64143fbeff ("unset RAMBlock idstr > when unregister MemoryRegion") I don't see it in that commit. I think it was part of the original split by Avi. > and from the archive in > http://lists.gnu.org/archive/html/qemu-devel/2014-04/msg00282.html, it > seems that it was trying to fix a reference count issue. >=20 > vmstate_unregister_ram() being a work around, let's remove it to fix > the current SEGV issue > and let's try to find a fix for the initial ref > count issue if we can reproduce. >=20 > Signed-off-by: C=E9dric Le Goater What kind of testing did you do on this patch? Could you include that info in the commit log pls? I think you need to at least add/remove some devices, then migrate. > --- > hw/pci/pci.c | 11 ----------- > 1 file changed, 11 deletions(-) >=20 > diff --git a/hw/pci/pci.c b/hw/pci/pci.c > index 80bc45930dee..78bf74e19f22 100644 > --- a/hw/pci/pci.c > +++ b/hw/pci/pci.c > @@ -191,7 +191,6 @@ static PCIBus *pci_find_bus_nr(PCIBus *bus, int bus= _num); > static void pci_update_mappings(PCIDevice *d); > static void pci_irq_handler(void *opaque, int irq_num, int level); > static void pci_add_option_rom(PCIDevice *pdev, bool is_default_rom, E= rror **); > -static void pci_del_option_rom(PCIDevice *pdev); > =20 > static uint16_t pci_default_sub_vendor_id =3D PCI_SUBVENDOR_ID_REDHAT_= QUMRANET; > static uint16_t pci_default_sub_device_id =3D PCI_SUBDEVICE_ID_QEMU; > @@ -1096,7 +1095,6 @@ static void pci_qdev_unrealize(DeviceState *dev, = Error **errp) > PCIDeviceClass *pc =3D PCI_DEVICE_GET_CLASS(pci_dev); > =20 > pci_unregister_io_regions(pci_dev); > - pci_del_option_rom(pci_dev); > =20 > if (pc->exit) { > pc->exit(pci_dev); > @@ -2262,15 +2260,6 @@ static void pci_add_option_rom(PCIDevice *pdev, = bool is_default_rom, > pci_register_bar(pdev, PCI_ROM_SLOT, 0, &pdev->rom); > } > =20 > -static void pci_del_option_rom(PCIDevice *pdev) > -{ > - if (!pdev->has_rom) > - return; > - > - vmstate_unregister_ram(&pdev->rom, &pdev->qdev); > - pdev->has_rom =3D false; > -} > - > /* > * On success, pci_add_capability() returns a positive value > * that the offset of the pci capability. > --=20 > 2.13.6