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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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@xxxxxxxxxx>
> --
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>


> 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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