[Xen-devel] Re: [PATCH] xen: fix interrupt routing

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Sat, 28 May 2011, Alexander Graf wrote:
> 
> On 26.05.2011, at 17:48, Stefano Stabellini wrote:
> 
> > xen: fix interrupt routing
> > 
> > - remove i440FX-xen and i440fx_write_config_xen
> > we don't need to intercept pci config writes to i440FX anymore;
> 
> Why not? In which version? Did anything below change? What about compat code? 
> Older hypervisor versions?

Nothing changed, I think it was a genuine mistake in the original patch
series: the intention was to catch the pci config writes to 0x60-0x63 to
reprogram the xen pci link routes accordingly (see
xen_piix_pci_write_config_client).  If I am not mistaken a similar thing
is done by non-Xen Qemu in piix3_update_irq_levels.


> > - introduce PIIX3-xen and piix3_write_config_xen
> > we do need to intercept pci config write to the PCI-ISA bridge to update
> > the PCI link routing;
> > 
> > - set the number of PIIX3-xen interrupts lines to 128;
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > 
> > diff --git a/hw/pc.h b/hw/pc.h
> > index 0dcbee7..6d5730b 100644
> > --- a/hw/pc.h
> > +++ b/hw/pc.h
> > @@ -176,7 +176,6 @@ struct PCII440FXState;
> > typedef struct PCII440FXState PCII440FXState;
> > 
> > PCIBus *i440fx_init(PCII440FXState **pi440fx_state, int *piix_devfn, 
> > qemu_irq *pic, ram_addr_t ram_size);
> > -PCIBus *i440fx_xen_init(PCII440FXState **pi440fx_state, int *piix3_devfn, 
> > qemu_irq *pic, ram_addr_t ram_size);
> > void i440fx_init_memory_mappings(PCII440FXState *d);
> > 
> > /* piix4.c */
> > diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> > index 9a22a8a..ba198de 100644
> > --- a/hw/pc_piix.c
> > +++ b/hw/pc_piix.c
> > @@ -124,11 +124,7 @@ static void pc_init1(ram_addr_t ram_size,
> >     isa_irq = qemu_allocate_irqs(isa_irq_handler, isa_irq_state, 24);
> > 
> >     if (pci_enabled) {
> > -        if (!xen_enabled()) {
> > -            pci_bus = i440fx_init(&i440fx_state, &piix3_devfn, isa_irq, 
> > ram_size);
> > -        } else {
> > -            pci_bus = i440fx_xen_init(&i440fx_state, &piix3_devfn, 
> > isa_irq, ram_size);
> > -        }
> > +        pci_bus = i440fx_init(&i440fx_state, &piix3_devfn, isa_irq, 
> > ram_size);
> >     } else {
> >         pci_bus = NULL;
> >         i440fx_state = NULL;
> > diff --git a/hw/piix_pci.c b/hw/piix_pci.c
> > index 7f1c4cc..3d73a42 100644
> > --- a/hw/piix_pci.c
> > +++ b/hw/piix_pci.c
> > @@ -40,6 +40,7 @@ typedef PCIHostState I440FXState;
> > 
> > #define PIIX_NUM_PIC_IRQS       16      /* i8259 * 2 */
> > #define PIIX_NUM_PIRQS          4ULL    /* PIRQ[A-D] */
> > +#define XEN_PIIX_NUM_PIRQS      128ULL
> > #define PIIX_PIRQC              0x60
> > 
> > typedef struct PIIX3State {
> > @@ -78,6 +79,8 @@ struct PCII440FXState {
> > #define I440FX_SMRAM    0x72
> > 
> > static void piix3_set_irq(void *opaque, int pirq, int level);
> > +static void piix3_write_config_xen(PCIDevice *dev,
> > +                               uint32_t address, uint32_t val, int len);
> > 
> > /* return the global irq number corresponding to a given device irq
> >    pin. We could also use the bus number to have a more precise
> > @@ -173,13 +176,6 @@ static void i440fx_write_config(PCIDevice *dev,
> >     }
> > }
> > 
> > -static void i440fx_write_config_xen(PCIDevice *dev,
> > -                                    uint32_t address, uint32_t val, int 
> > len)
> > -{
> > -    xen_piix_pci_write_config_client(address, val, len);
> > -    i440fx_write_config(dev, address, val, len);
> > -}
> > -
> > static int i440fx_load_old(QEMUFile* f, void *opaque, int version_id)
> > {
> >     PCII440FXState *d = opaque;
> > @@ -267,8 +263,17 @@ static PCIBus *i440fx_common_init(const char 
> > *device_name,
> >     d = pci_create_simple(b, 0, device_name);
> >     *pi440fx_state = DO_UPCAST(PCII440FXState, dev, d);
> > 
> > -    piix3 = DO_UPCAST(PIIX3State, dev,
> > -                      pci_create_simple_multifunction(b, -1, true, 
> > "PIIX3"));
> > +    if (xen_enabled()) {
> > +        piix3 = DO_UPCAST(PIIX3State, dev,
> > +                pci_create_simple_multifunction(b, -1, true, "PIIX3-xen"));
> > +        pci_bus_irqs(b, xen_piix3_set_irq, xen_pci_slot_get_pirq,
> > +                piix3, XEN_PIIX_NUM_PIRQS);
> 
> But with XEN_PIIX_NUM_PIRQS it's not a piix3 anymore, no? What's the reason 
> behind this change?
 
It is still a piix3, but also provides non-legacy interrupt links to the
IO-APIC.
The four pins of each PCI device on the bus not only are routed to the
normal four pirqs (programmed writing to 0x60-0x63, see above) but also
they are connected to the IO-APIC directly.
These additional routes can only be discovered through ACPI, so you need
matching ACPI tables. We used to build the old ACPI tables like this:

/* PRTA: APIC routing table (via non-legacy IOAPIC GSIs). */
printf("Name(PRTA, Package() {\n");
for ( dev = 1; dev < 32; dev++ )
    for ( intx = 0; intx < 4; intx++ ) /* INTA-D */
        printf("Package(){0x%04xffff, %u, 0, %u},\n",
               dev, intx, ((dev*4+dev/8+intx)&31)+16);
printf("})\n");



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