RE: [PATCH] xen: rework pci_piix3_xen_ide_unplug

[Paul Durrant]

> -----Original Message-----
> From: Anthony PERARD <anthony.perard@citrix.com>
> Sent: 18 September 2020 15:53
> To: qemu-devel@nongnu.org
> Cc: Paul Durrant <paul@xen.org>; Stefano Stabellini <sstabellini@kernel.org>; 
> Anthony PERARD
> <anthony.perard@citrix.com>; John Snow <jsnow@redhat.com>; 
> qemu-block@nongnu.org
> Subject: [PATCH] xen: rework pci_piix3_xen_ide_unplug
> 
> This is to allow IDE disks to be unplugged when adding to QEMU via:
>     -drive file=/root/disk_file,if=none,id=ide-disk0,format=raw
>     -device ide-hd,drive=ide-disk0,bus=ide.0,unit=0
> 
> as the current code only works for disk added with:
>     -drive file=/root/disk_file,if=ide,index=0,media=disk,format=raw
> 
> Since the code already have the IDE controller as `dev`, we don't need
> to use the legacy DriveInfo to find all the drive we want to unplug.
> We can simply use `blk` from the controller, as it kind of was already
> assume to be the same, by setting it to NULL.
> 
> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> ---
>  hw/ide/piix.c | 27 +++++++++++++--------------
>  1 file changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/hw/ide/piix.c b/hw/ide/piix.c
> index b402a936362b..16fcbe58d6fe 100644
> --- a/hw/ide/piix.c
> +++ b/hw/ide/piix.c
> @@ -164,30 +164,29 @@ static void pci_piix_ide_realize(PCIDevice *dev, Error 
> **errp)
>  int pci_piix3_xen_ide_unplug(DeviceState *dev, bool aux)
>  {
>      PCIIDEState *pci_ide;
> -    DriveInfo *di;
>      int i;
>      IDEDevice *idedev;
> +    IDEBus *idebus;
> +    BlockBackend *blk;
> 
>      pci_ide = PCI_IDE(dev);
> 
>      for (i = aux ? 1 : 0; i < 4; i++) {
> -        di = drive_get_by_index(IF_IDE, i);
> -        if (di != NULL && !di->media_cd) {
> -            BlockBackend *blk = blk_by_legacy_dinfo(di);
> -            DeviceState *ds = blk_get_attached_dev(blk);
> +        idebus = &pci_ide->bus[i / 2];
> +        blk = idebus->ifs[i % 2].blk;
> 
> -            blk_drain(blk);
> -            blk_flush(blk);
> -
> -            if (ds) {
> -                blk_detach_dev(blk, ds);
> -            }
> -            pci_ide->bus[di->bus].ifs[di->unit].blk = NULL;
> +        if (blk && idebus->ifs[i%2].drive_kind != IDE_CD) {

Spaces around '%'

>              if (!(i % 2)) {
> -                idedev = pci_ide->bus[di->bus].master;
> +                idedev = idebus->master;
>              } else {
> -                idedev = pci_ide->bus[di->bus].slave;
> +                idedev = idebus->slave;
>              }

Perhaps use a ternary operator here rather than if/else. Also there are 3 uses 
'i % 2' so I wonder whether a local 'device index'
variable might be neater.

  Paul

> +
> +            blk_drain(blk);
> +            blk_flush(blk);
> +
> +            blk_detach_dev(blk, DEVICE(idedev));
> +            idebus->ifs[i % 2].blk = NULL;
>              idedev->conf.blk = NULL;
>              monitor_remove_blk(blk);
>              blk_unref(blk);
> --
> Anthony PERARD