On Thu, Nov 11, 2010 at 11:03:19PM -0700, Alex Williamson wrote:
> On Fri, 2010-11-12 at 07:22 +0200, Michael S. Tsirkin wrote:
> > On Thu, Nov 11, 2010 at 07:55:01PM -0700, Alex Williamson wrote:
> > > Make use of wmask, just like the rest of config space.
> > >
> > > Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > > ---
> > >
> > > hw/pci.c | 19 ++++++++-----------
> > > 1 files changed, 8 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/hw/pci.c b/hw/pci.c
> > > index 92aaa85..12c47ac 100644
> > > --- a/hw/pci.c
> > > +++ b/hw/pci.c
> > > @@ -1175,13 +1175,14 @@ uint32_t pci_default_read_config(PCIDevice *d,
> > > return pci_read_config(d, address, len);
> > > }
> > >
> > > -static void pci_write_config(PCIDevice *pci_dev,
> > > - uint32_t address, uint32_t val, int len)
> > > +static void pci_write_config(PCIDevice *d, uint32_t addr, uint32_t val, int l)
> > > {
> > > int i;
> > > - for (i = 0; i < len; i++) {
> > > - pci_dev->config[address + i] = val & 0xff;
> > > - val >>= 8;
> > > + uint32_t config_size = pci_config_size(d);
> > > +
> > > + for (i = 0; i < l && addr + i < config_size; val >>= 8, ++i) {
> > > + uint8_t wmask = d->wmask[addr + i];
> > > + d->config[addr + i] = (d->config[addr + i] & ~wmask) | (val & wmask);
> > > }
> > > }
> > >
> >
> >
> > Let's not name an internal static helper pci_write_config.
> > This is really update_config_by_mask or something like that.
> > But see below: maybe we don't need it at all?
>
> The function already exists, I just made it do what it seems like it
> should have been doing already.
Yep. But since you are rewriting this function - could you rename it as
well?
> > > @@ -1207,18 +1208,14 @@ void pci_default_cap_write_config(PCIDevice *pci_dev,
> > >
> > > void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val, int l)
> > > {
> > > - int i, was_irq_disabled = pci_irq_disabled(d);
> > > - uint32_t config_size = pci_config_size(d);
> > > + int was_irq_disabled = pci_irq_disabled(d);
> > >
> > > if (pci_access_cap_config(d, addr, l)) {
> > > d->cap.config_write(d, addr, val, l);
> > > return;
> > > }
> > >
> >
> > I would like to also examine the need for _cap_
> > functions. Why can assigned devices just do
> >
> > pci_default_write_config
> > if (range_overlap(...msi)) {
> > }
> > if (range_overlap(...msix)) {
> > }
> > and then we could remove all the _cap_ extensions
> > altogether?
>
> I think that somewhere we need to track what capabilities are at what
> offset, config space isn't a performance path, but that look horribly
> inefficient and gets worse with more capabilities.
Looks like premature optimization to me. I guess when we get more than
say 8 capabilities to support, I'll start to worry.
Even then, these optimizations are better internal in pci core.
> Why don't we define capability id 0xff as normal config space (first 64
> bytes), then add the capability id to read/write_config (this is what
> vfio does). Then the driver can split capability handling off from
> their main functions if they want.
My feeling is we need higher level APIs than 'capability write'.
Otherwise we get the PCI config handling all over the place.
E.g. a callback when msi is enabled/disabled would make sense,
so that pci core can keep track of current state and only notify
the device when there are things to do.
> Anyway, I think such an improvement
> could be added incrementally later. Thanks,
>
> Alex
Sure.
> > > - for (i = 0; i < l && addr + i < config_size; val >>= 8, ++i) {
> > > - uint8_t wmask = d->wmask[addr + i];
> > > - d->config[addr + i] = (d->config[addr + i] & ~wmask) | (val & wmask);
> > > - }
> > > + pci_write_config(d, addr, val, l);
> > >
> > > #ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
> > > if (kvm_enabled() && kvm_irqchip_in_kernel() &&
>
>
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