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i0HjnLoJP5jDcoMTabZTIazXmJz3pKM11HYJ5/ZsTIf3ZRJJKIvXJpbmcAPVwTZII6XxiJdh RSSX4Mvd5pL/+5WI6NTdW6DMfigTtdd85fe6PwBNVJL2ZvBfsBJZ5rxg1TOH3KLsYBqBTgW2 glQofxhkJhDEcvjLhe3Y2BlbCWKOmvM8XS9TRt0OwUs= Message-ID: <6eb1dbda-85fe-de7c-613c-a6871fc2d28f@redhat.com> Date: Mon, 9 Sep 2019 14:13:02 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <1568049517-10261-1-git-send-email-andychiu@synology.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 09 Sep 2019 18:13:18 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] ahci: enable pci bus master MemoryRegion before loading ahci engines X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/9/19 1:18 PM, andychiu via Qemu-devel wrote: > If Windows 10 guests have enabled 'turn off hard disk after idle' > option in power settings, and the guest has a SATA disk plugged in, > the SATA disk will be turned off after a specified idle time. > If the guest is live migrated or saved/loaded with its SATA disk > turned off, the following error will occur: > > qemu-system-x86_64: AHCI: Failed to start FIS receive engine: bad FIS receive buffer address > qemu-system-x86_64: Failed to load ich9_ahci:ahci > qemu-system-x86_64: error while loading state for instance 0x0 of device '0000:00:1a.0/ich9_ahci' > qemu-system-x86_64: load of migration failed: Operation not permitted > Oof. That can't have been fun to discover. > Observation from trace logs shows that a while after Windows 10 turns off > a SATA disk (IDE disks don't have the following behavior), > it will disable the PCI_COMMAND_MASTER flag of the pci device containing > the ahci device. When the the disk is turning back on, > the PCI_COMMAND_MASTER flag will be restored first. > But if the guest is migrated or saved/loaded while the disk is off, > the post_load callback of ahci device, ahci_state_post_load(), will fail > at ahci_cond_start_engines() if the MemoryRegion > pci_dev->bus_master_enable_region is not enabled, with pci_dev pointing > to the PCIDevice struct containing the ahci device. > > This patch enables pci_dev->bus_master_enable_region before calling > ahci_cond_start_engines() in ahci_state_post_load(), and restore the > MemoryRegion to its original state afterwards.> This looks good to me from an AHCI perspective, but I'm not as clear on the implications of toggling the MemoryRegion, so I have some doubts. MST, can you chime in and clear my confusion? I suppose when the PCI_COMMAND_MASTER bit is turned off, we disable the memory region, as a guest would be unable to establish a new mapping in this time, so it makes sense that the attempt to map it fails. What's less clear to me is what happens to existing mappings when a region is disabled. Are they invalidated? If so, does it make sense that we are trying to establish a mapping here at all? Maybe it's absolutely correct that this fails. (I suppose, though, that the simple toggling of the region won't be a guest-visible event, so it's probably safe to do. Right?) What I find weird for AHCI is this: We try to engage the CLB mapping before the FIS mapping, but we fail at the FIS mapping. So why is PORT_CMD_FIS_RX set while PORT_CMD_START is unset? It kind of looks like we only half-heartedly stopped the AHCI device. Maybe that's just what Windows does, but I wonder if there's a bug where we're erroneously leaving PORT_CMD_FIS_RX set when we've been disabled. It seems like the guest would need to re-set the mappings anyway, so maybe trying to restore a stale mapping is not the right thing to do. Andy, if you have traces left over: What AHCI registers does Windows touch when it disables the AHCI device? What registers does it touch when it re-engages it? I just want to make sure I'm not leaving something dangling by accident. --js > Signed-off-by: andychiu > --- > hw/ide/ahci.c | 53 ++++++++++++++++++++++++++++++++++++----------------- > 1 file changed, 36 insertions(+), 17 deletions(-) > > diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c > index d45393c..83f8c30 100644 > --- a/hw/ide/ahci.c > +++ b/hw/ide/ahci.c > @@ -1649,33 +1649,52 @@ static const VMStateDescription vmstate_ahci_device = { > }, > }; > > +static int ahci_state_load_engines(AHCIState *s, AHCIDevice *ad) > +{ > + AHCIPortRegs *pr = &ad->port_regs; > + DeviceState *dev_state = s->container; > + PCIDevice *pci_dev = (PCIDevice *) object_dynamic_cast(OBJECT(dev_state), > + TYPE_PCI_DEVICE); > + bool pci_bus_master_enabled = pci_dev->bus_master_enable_region.enabled; > + > + if (!(pr->cmd & PORT_CMD_START) && (pr->cmd & PORT_CMD_LIST_ON)) { > + error_report("AHCI: DMA engine should be off, but status bit " > + "indicates it is still running."); > + return -1; > + } > + if (!(pr->cmd & PORT_CMD_FIS_RX) && (pr->cmd & PORT_CMD_FIS_ON)) { > + error_report("AHCI: FIS RX engine should be off, but status bit " > + "indicates it is still running."); > + return -1; > + } > + > + memory_region_set_enabled(&pci_dev->bus_master_enable_region, true); > + > + /* > + * After a migrate, the DMA/FIS engines are "off" and > + * need to be conditionally restarted > + */ > + pr->cmd &= ~(PORT_CMD_LIST_ON | PORT_CMD_FIS_ON); > + if (ahci_cond_start_engines(ad) != 0) { > + return -1; > + } > + memory_region_set_enabled(&pci_dev->bus_master_enable_region, > + pci_bus_master_enabled); > + > + return 0; > +} > + > static int ahci_state_post_load(void *opaque, int version_id) > { > int i, j; > struct AHCIDevice *ad; > NCQTransferState *ncq_tfs; > - AHCIPortRegs *pr; > AHCIState *s = opaque; > > for (i = 0; i < s->ports; i++) { > ad = &s->dev[i]; > - pr = &ad->port_regs; > - > - if (!(pr->cmd & PORT_CMD_START) && (pr->cmd & PORT_CMD_LIST_ON)) { > - error_report("AHCI: DMA engine should be off, but status bit " > - "indicates it is still running."); > - return -1; > - } > - if (!(pr->cmd & PORT_CMD_FIS_RX) && (pr->cmd & PORT_CMD_FIS_ON)) { > - error_report("AHCI: FIS RX engine should be off, but status bit " > - "indicates it is still running."); > - return -1; > - } > > - /* After a migrate, the DMA/FIS engines are "off" and > - * need to be conditionally restarted */ > - pr->cmd &= ~(PORT_CMD_LIST_ON | PORT_CMD_FIS_ON); > - if (ahci_cond_start_engines(ad) != 0) { > + if (ahci_state_load_engines(s, ad)) { > return -1; > } > >