On Thu, Mar 29, 2012 at 6:28 PM, Andy Whitcroft <apw@xxxxxxxxxxxxx> wrote: > When we are hosted on a Hyper-V hypervisor the guest disks are exposed > both via the Hyper-V paravirtualised drivers and via an emulated SATA disk > controller. We want to use the paravirtualised drivers where possible as > they are much more performant. The Hyper-V paravirtualised drivers only > expose the virtual hard disk devices, the CDROM/DVD devices must still > be enumerated on the virtualised SATA controller. As we have no control > over kernel probe order for these two drivers especially when one driver > is builtin to the kernel and the other a module, we need to prevent the > ata_piix driver from claiming the disks devices by default when running > on a Hyper-V hypervisor. > > When enumerating the drives look at the aquired device ID and if it > appears to be a disk device then report it as disconnected. Limit this > behaviour to when we have detected a Hyper-V hypervisor. Finally allow > this behaviour to be overriden via a new module parameter. > > BugLink: http://bugs.launchpad.net/bugs/929545 > BugLink: http://bugs.launchpad.net/bugs/942316 > Signed-off-by: Andy Whitcroft <apw@xxxxxxxxxxxxx> > --- > drivers/ata/ata_piix.c | 29 +++++++++++++++++++++++++++++ > 1 files changed, 29 insertions(+), 0 deletions(-) > > This was discovered when doing some boot testing on a Hyper-V > host. Performance was found to be bad as out builtin ata_piix > driver was grabbing the disks. I am Cc:ing a couple of the > Microsoft people who worked on the HV driver set as well. > > Note that the device id data is converted from device to host > order in the caller which makes examining the data problematic. > As this code only make sense on X86 and we know we are in > matching order we can access the data without first fixing it. > Alternativly we could add a new callback from the ata core > after the code has been fixed for validation. > > Comments? > > -apw > > diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c > index 68013f9..64895f8 100644 > --- a/drivers/ata/ata_piix.c > +++ b/drivers/ata/ata_piix.c > @@ -94,6 +94,9 @@ > #include <scsi/scsi_host.h> > #include <linux/libata.h> > #include <linux/dmi.h> > +#ifdef CONFIG_X86 > +#include <asm/hypervisor.h> > +#endif > > #define DRV_NAME "ata_piix" > #define DRV_VERSION "2.13" > @@ -188,6 +191,29 @@ static int piix_pci_device_resume(struct pci_dev *pdev); > > static unsigned int in_module_init = 1; > > +static int prefer_ms_hyperv = 1; > + > +unsigned int ata_piix_read_id(struct ata_device *dev, > + struct ata_taskfile *tf, u16 *id) > +{ > + int ret = ata_do_dev_read_id(dev, tf, id); > + > +#ifdef CONFIG_X86 > + /* XXX: note that the device id is in little-endian order, the caller > + * will shift it to host order, but we are working with little-endian. > + * As this is _only_ used on x86 we can actually directly access it > + * as host is also little-endian. > + */ > + if (!ret && prefer_ms_hyperv && x86_hyper == &x86_hyper_ms_hyperv && > + ata_id_is_ata(id)) { > + ata_dev_printk(dev, KERN_WARNING, "ATA disk ignored deferring to Hyper-V paravirt driver\n"); > + > + return AC_ERR_DEV|AC_ERR_NODEV_HINT; > + } > +#endif > + return ret; > +} > + > static const struct pci_device_id piix_pci_tbl[] = { > /* Intel PIIX3 for the 430HX etc */ > { 0x8086, 0x7010, PCI_ANY_ID, PCI_ANY_ID, 0, 0, piix_pata_mwdma }, > @@ -359,6 +385,7 @@ static struct ata_port_operations piix_pata_ops = { > .set_piomode = piix_set_piomode, > .set_dmamode = piix_set_dmamode, > .prereset = piix_pata_prereset, > + .read_id = ata_piix_read_id, > }; > > static struct ata_port_operations piix_vmw_ops = { > @@ -1703,3 +1730,5 @@ static void __exit piix_exit(void) > > module_init(piix_init); > module_exit(piix_exit); > + > +module_param(prefer_ms_hyperv, int, 0); Jeff, any thoughts on this patch? -apw -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
