Re: [PATCH v2] xen-platform: separate unplugging of NVMe disks

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Stefano Stabellini [mailto:sstabellini@kernel.org]
> Sent: 24 March 2017 00:51
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: qemu-devel@nongnu.org; xen-devel@lists.xenproject.org; Stefano
> Stabellini <sstabellini@kernel.org>; Anthony Perard
> <anthony.perard@citrix.com>
> Subject: Re: [PATCH v2] xen-platform: separate unplugging of NVMe disks
> 
> On Thu, 23 Mar 2017, Paul Durrant wrote:
> > Commit 090fa1c8 "add support for unplugging NVMe disks..." extended the
> > existing disk unplug flag to cover NVMe disks as well as IDE and SCSI.
> >
> > The recent thread on the xen-devel mailing list [1] has highlighted that
> > this is not desirable behaviour: PV frontends should be able to distinguish
> > NVMe disks from other types of disk and should have separate control
> over
> > whether they are unplugged.
> >
> > This patch defines a new bit in the unplug mask for this purpose and also
> > tidies up the definitions of, and improves the comments regarding, the
> > previously exiting bits in the protocol.
> >
> > [1] https://lists.xen.org/archives/html/xen-devel/2017-03/msg02924.html
> >
> > Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> > --
> > Cc: Stefano Stabellini <sstabellini@kernel.org>
> > Cc: Anthony Perard <anthony.perard@citrix.com>
> >
> > NOTE: A companion patch will be submitted to xen-devel to align the
> >       unplug protocol documentation once this patch is acked.
> 
> The companion patch needs to be acked before this patch gets applied. In
> fact, I would prefer if the changeset of the Xen commit was added to
> this patch description.
> 
> If you add that, then you can repost this with
> 
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> 

Ok. I'll cc you on the xen docs patch too.

  Paul

> 
> > v2:
> > - Fix the commit comment
> > ---
> >  hw/i386/xen/xen_platform.c | 47
> ++++++++++++++++++++++++++++++++++------------
> >  1 file changed, 35 insertions(+), 12 deletions(-)
> >
> > diff --git a/hw/i386/xen/xen_platform.c b/hw/i386/xen/xen_platform.c
> > index 6010f35..983d532 100644
> > --- a/hw/i386/xen/xen_platform.c
> > +++ b/hw/i386/xen/xen_platform.c
> > @@ -87,10 +87,30 @@ static void log_writeb(PCIXenPlatformState *s, char
> val)
> >      }
> >  }
> >
> > -/* Xen Platform, Fixed IOPort */
> > -#define UNPLUG_ALL_DISKS 1
> > -#define UNPLUG_ALL_NICS 2
> > -#define UNPLUG_AUX_IDE_DISKS 4
> > +/*
> > + * Unplug device flags.
> > + *
> > + * The logic got a little confused at some point in the past but this is
> > + * what they do now.
> > + *
> > + * bit 0: Unplug all IDE and SCSI disks.
> > + * bit 1: Unplug all NICs.
> > + * bit 2: Unplug IDE disks except primary master. This is overridden if
> > + *        bit 0 is also present in the mask.
> > + * bit 3: Unplug all NVMe disks.
> > + *
> > + */
> > +#define _UNPLUG_IDE_SCSI_DISKS 0
> > +#define UNPLUG_IDE_SCSI_DISKS (1u << _UNPLUG_IDE_SCSI_DISKS)
> > +
> > +#define _UNPLUG_ALL_NICS 1
> > +#define UNPLUG_ALL_NICS (1u << _UNPLUG_ALL_NICS)
> > +
> > +#define _UNPLUG_AUX_IDE_DISKS 2
> > +#define UNPLUG_AUX_IDE_DISKS (1u << _UNPLUG_AUX_IDE_DISKS)
> > +
> > +#define _UNPLUG_NVME_DISKS 3
> > +#define UNPLUG_NVME_DISKS (1u << _UNPLUG_NVME_DISKS)
> >
> >  static void unplug_nic(PCIBus *b, PCIDevice *d, void *o)
> >  {
> > @@ -111,7 +131,7 @@ static void unplug_disks(PCIBus *b, PCIDevice *d,
> void *opaque)
> >  {
> >      uint32_t flags = *(uint32_t *)opaque;
> >      bool aux = (flags & UNPLUG_AUX_IDE_DISKS) &&
> > -        !(flags & UNPLUG_ALL_DISKS);
> > +        !(flags & UNPLUG_IDE_SCSI_DISKS);
> >
> >      /* We have to ignore passthrough devices */
> >      if (!strcmp(d->name, "xen-pci-passthrough")) {
> > @@ -124,12 +144,16 @@ static void unplug_disks(PCIBus *b, PCIDevice *d,
> void *opaque)
> >          break;
> >
> >      case PCI_CLASS_STORAGE_SCSI:
> > -    case PCI_CLASS_STORAGE_EXPRESS:
> >          if (!aux) {
> >              object_unparent(OBJECT(d));
> >          }
> >          break;
> >
> > +    case PCI_CLASS_STORAGE_EXPRESS:
> > +        if (flags & UNPLUG_NVME_DISKS) {
> > +            object_unparent(OBJECT(d));
> > +        }
> > +
> >      default:
> >          break;
> >      }
> > @@ -147,10 +171,9 @@ static void platform_fixed_ioport_writew(void
> *opaque, uint32_t addr, uint32_t v
> >      switch (addr) {
> >      case 0: {
> >          PCIDevice *pci_dev = PCI_DEVICE(s);
> > -        /* Unplug devices.  Value is a bitmask of which devices to
> > -           unplug, with bit 0 the disk devices, bit 1 the network
> > -           devices, and bit 2 the non-primary-master IDE devices. */
> > -        if (val & (UNPLUG_ALL_DISKS | UNPLUG_AUX_IDE_DISKS)) {
> > +        /* Unplug devices. See comment above flag definitions */
> > +        if (val & (UNPLUG_IDE_SCSI_DISKS | UNPLUG_AUX_IDE_DISKS |
> > +                   UNPLUG_NVME_DISKS)) {
> >              DPRINTF("unplug disks\n");
> >              pci_unplug_disks(pci_dev->bus, val);
> >          }
> > @@ -338,14 +361,14 @@ static void xen_platform_ioport_writeb(void
> *opaque, hwaddr addr,
> >               * If VMDP was to control both disk and LAN it would use 4.
> >               * If it controlled just disk or just LAN, it would use 8 below.
> >               */
> > -            pci_unplug_disks(pci_dev->bus, UNPLUG_ALL_DISKS);
> > +            pci_unplug_disks(pci_dev->bus, UNPLUG_IDE_SCSI_DISKS);
> >              pci_unplug_nics(pci_dev->bus);
> >          }
> >          break;
> >      case 8:
> >          switch (val) {
> >          case 1:
> > -            pci_unplug_disks(pci_dev->bus, UNPLUG_ALL_DISKS);
> > +            pci_unplug_disks(pci_dev->bus, UNPLUG_IDE_SCSI_DISKS);
> >              break;
> >          case 2:
> >              pci_unplug_nics(pci_dev->bus);
> > --
> > 2.1.4
> >

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