[Qemu-devel] Re: [PATCH 4/4] pci: interrupt disable bit support

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Nov 26, 2009 at 11:53:16AM +0200, Michael S. Tsirkin wrote:
> On Thu, Nov 26, 2009 at 12:04:51PM +0900, Isaku Yamahata wrote:
> > On Wed, Nov 25, 2009 at 06:59:06PM +0200, Michael S. Tsirkin wrote:
> > > interrupt disable bit is mandatory in PCI spec,
> > > so we must implement it to be spec compliant.
> > > 
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > ---
> > >  hw/pci.c |   57 ++++++++++++++++++++++++++++++++++++++++-----------------
> > >  hw/pci.h |    4 ++++
> > >  2 files changed, 44 insertions(+), 17 deletions(-)
> > > 
> > > diff --git a/hw/pci.c b/hw/pci.c
> > > index 844664b..3daae46 100644
> > > --- a/hw/pci.c
> > > +++ b/hw/pci.c
> > > @@ -114,12 +114,43 @@ static void pci_update_irq_status(PCIDevice *dev)
> > >      }
> > >  }
> > >  
> > > +static void pci_change_irq_level(PCIDevice *pci_dev, int irq_num, int change)
> > > +{
> > > +    PCIBus *bus;
> > > +    for (;;) {
> > > +        bus = pci_dev->bus;
> > > +        irq_num = bus->map_irq(pci_dev, irq_num);
> > > +        if (bus->set_irq)
> > > +            break;
> > > +        pci_dev = bus->parent_dev;
> > > +    }
> > > +    bus->irq_count[irq_num] += change;
> > > +    bus->set_irq(bus->irq_opaque, irq_num, bus->irq_count[irq_num] != 0);
> > 
> > Let's use ! instead of != 0 for consistency.
> > 
> 
> This patch simply moves code, so it's better to keep it
> the same - this way git blame can find it.
> A separate patch to clean this might be a good idea.
> 
> > > +}
> > > +
> > > +/* Update irq disabled field after config space change,
> > > + * assert/deassert interrupts if necessary. */
> > > +static void pci_update_irq_disabled(PCIDevice *d)
> > > +{
> > > +    int i;
> > > +    int disabled = !!(pci_get_word(d->config + PCI_COMMAND) &
> > > +                      PCI_COMMAND_INTX_DISABLE);
> > > +    if (disabled == d->irq_disabled)
> > > +        return;
> > > +    d->irq_disabled = disabled;
> > > +    for (i = 0; i < ARRAY_SIZE(d->irq_state); ++i) {
> > > +        int state = d->irq_state[i];
> > > +        pci_change_irq_level(d, i, disabled ? -state : state);
> > > +    }
> > > +}
> > > +
> > 
> > "if (!changed) return" check is in pci_set_irq().
> > So if d->irq_state[i] == 0, bus->set_irq() will be called again.
> > I suppose this isn't your intention.
> 
> Good catch, thanks!

Thinking about this more, in fact, it is harmless to call set_irq
with the same level as th old one, and this
is not on datapath.
So yes, this is the intention.

> > I suppose !changed check should be in pci_change_irq_level() instead of pci_set_irq().
> > 
> 
> The fix is different: in fact pci_update_irq_disabled
> should never call pci_change_irq_level with change value 0.
> that -state should have been 1 - state.
> I'll fix this. Thanks!

In fact, you were right.
While calling pci_change_irq_level with change 0 is harmless,
it's cleaner to move the check within that function.
I'll do that.

> > >  static void pci_device_reset(PCIDevice *dev)
> > >  {
> > >      int r;
> > >  
> > >      memset(dev->irq_state, 0, sizeof dev->irq_state);
> > >      dev->irq_status = 0;
> > > +    dev->irq_disabled = 0;
> > >      pci_update_irq_status(dev);
> > >      dev->config[PCI_COMMAND] &= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY |
> > >                                    PCI_COMMAND_MASTER);
> > > @@ -345,6 +376,7 @@ int pci_device_load(PCIDevice *s, QEMUFile *f)
> > >      }
> > >      /* Restore the interrupt status bit. */
> > >      pci_update_irq_status(s);
> > > +    pci_update_irq_disabled(s);
> > >      return ret;
> > >  }
> > >  
> > > @@ -458,7 +490,8 @@ static void pci_init_wmask(PCIDevice *dev)
> > >      dev->wmask[PCI_CACHE_LINE_SIZE] = 0xff;
> > >      dev->wmask[PCI_INTERRUPT_LINE] = 0xff;
> > >      pci_set_word(dev->wmask + PCI_COMMAND,
> > > -                 PCI_COMMAND_IO | PCI_COMMAND_MEMORY | PCI_COMMAND_MASTER);
> > > +                 PCI_COMMAND_IO | PCI_COMMAND_MEMORY | PCI_COMMAND_MASTER |
> > > +                 PCI_COMMAND_INTX_DISABLE);
> > >  
> > >      memset(dev->wmask + PCI_CONFIG_HEADER_SIZE, 0xff,
> > >             config_size - PCI_CONFIG_HEADER_SIZE);
> > > @@ -903,26 +936,14 @@ void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val, int l)
> > >          ranges_overlap(addr, l, PCI_ROM_ADDRESS1, 4) ||
> > >          range_covers_byte(addr, l, PCI_COMMAND))
> > >          pci_update_mappings(d);
> > > +
> > > +    if (range_covers_byte(addr, l, PCI_COMMAND))
> > > +        pci_update_irq_disabled(d);
> > >  }
> > >  
> > >  /***********************************************************/
> > >  /* generic PCI irq support */
> > >  
> > > -static void pci_change_irq_level(PCIDevice *pci_dev, int irq_num, int change)
> > > -{
> > > -    PCIBus *bus;
> > > -    for (;;) {
> > > -        bus = pci_dev->bus;
> > > -        irq_num = bus->map_irq(pci_dev, irq_num);
> > > -        if (bus->set_irq)
> > > -            break;
> > > -        pci_dev = bus->parent_dev;
> > > -    }
> > > -    bus->irq_count[irq_num] += change;
> > > -    bus->set_irq(bus->irq_opaque, irq_num, bus->irq_count[irq_num] != 0);
> > > -}
> > > -
> > > -
> > >  /* 0 <= irq_num <= 3. level must be 0 or 1 */
> > >  static void pci_set_irq(void *opaque, int irq_num, int level)
> > >  {
> > > @@ -935,7 +956,9 @@ static void pci_set_irq(void *opaque, int irq_num, int level)
> > >  
> > >      pci_dev->irq_state[irq_num] = level;
> > >      pci_dev->irq_status += change;
> > > -    pci_update_irq_status(s);
> > > +    pci_update_irq_status(pci_dev);
> > > +    if (pci_dev->irq_disabled)
> > > +        return;
> > >      pci_change_irq_level(pci_dev, irq_num, change);
> > >  }
> > >  
> > > diff --git a/hw/pci.h b/hw/pci.h
> > > index c3f2c3f..994b8bc 100644
> > > --- a/hw/pci.h
> > > +++ b/hw/pci.h
> > > @@ -101,6 +101,7 @@ typedef struct PCIIORegion {
> > >  #define  PCI_COMMAND_IO		0x1	/* Enable response in I/O space */
> > >  #define  PCI_COMMAND_MEMORY	0x2	/* Enable response in Memory space */
> > >  #define  PCI_COMMAND_MASTER	0x4	/* Enable bus master */
> > > +#define  PCI_COMMAND_INTX_DISABLE 0x400 /* INTx Emulation Disable */
> > >  #define PCI_STATUS              0x06    /* 16 bits */
> > >  #define  PCI_STATUS_INTERRUPT   0x08
> > >  #define PCI_REVISION_ID         0x08    /* 8 bits  */
> > > @@ -226,6 +227,9 @@ struct PCIDevice {
> > >      /* Sum of all irq levels. Used to implement irq status register. */
> > >      int irq_status;
> > >  
> > > +    /* Whether interrupts are disabled by command bit. */
> > > +    int irq_disabled;
> > > +
> > >      /* Capability bits */
> > >      uint32_t cap_present;
> > >  
> > 
> > -- 
> > yamahata