Re: [Xen-devel] [PATCH v2] qemu/xen: Add 64 bits big bar support on qemu

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 26 Sep 2012, Hao, Xudong wrote:
> > -----Original Message-----
> > From: Stefano Stabellini [mailto:stefano.stabellini@xxxxxxxxxxxxx]
> > Sent: Tuesday, September 25, 2012 6:52 PM
> > To: Hao, Xudong
> > Cc: Stefano Stabellini; xen-devel@xxxxxxxxxxxxx; qemu-devel@xxxxxxxxxx;
> > Zhang, Xiantao
> > Subject: Re: [PATCH v2] qemu/xen: Add 64 bits big bar support on qemu
> > 
> > On Tue, 25 Sep 2012, Xudong Hao wrote:
> > > Changes from v1:
> > > - Rebase to qemu upstream from qemu-xen
> > 
> > Thanks. Please run scripts/checkpatch.pl on this patch, you'll find
> > some cody style issues that need to be fixed.
> > 
> OK, will use this scripts to check code style.
> 
> > 
> > > Currently it is assumed PCI device BAR access < 4G memory. If there is 
> > > such a
> > > device whose BAR size is larger than 4G, it must access > 4G memory
> > address.
> > > This patch enable the 64bits big BAR support on qemu.
> > >
> > > Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx>
> > > Signed-off-by: Xiantao Zhang <xiantao.zhang@xxxxxxxxx>
> > > ---
> > >  hw/xen_pt.c             |   16 ++++++++--------
> > >  hw/xen_pt_config_init.c |   42
> > +++++++++++++++++++++++++++++-------------
> > >
> > > diff --git a/hw/xen_pt.c b/hw/xen_pt.c
> > > index 307119a..2a8bcf3 100644
> > > --- a/hw/xen_pt.c
> > > +++ b/hw/xen_pt.c
> > > @@ -403,21 +403,21 @@ static int
> > xen_pt_register_regions(XenPCIPassthroughState *s)
> > >
> > >          s->bases[i].access.u = r->base_addr;
> > >
> > > -        if (r->type & XEN_HOST_PCI_REGION_TYPE_IO) {
> > > +        if (r->type & XEN_HOST_PCI_REGION_TYPE_IO)
> > >              type = PCI_BASE_ADDRESS_SPACE_IO;
> > > -        } else {
> > > +        else if (r->type & XEN_HOST_PCI_REGION_TYPE_MEM_64)
> > > +            type = PCI_BASE_ADDRESS_MEM_TYPE_64;
> > > +        else if (r->type & XEN_HOST_PCI_REGION_TYPE_PREFETCH)
> > > +            type |= PCI_BASE_ADDRESS_MEM_PREFETCH;
> > > +        else
> > >              type = PCI_BASE_ADDRESS_SPACE_MEMORY;
> > > -            if (r->type & XEN_HOST_PCI_REGION_TYPE_PREFETCH) {
> > > -                type |= PCI_BASE_ADDRESS_MEM_PREFETCH;
> > > -            }
> > > -        }
> > 
> > Aside from the cody style issue here, this changes the behavior for type
> > PCI_BASE_ADDRESS_SPACE_MEMORY. Before we could have:
> > 
> > type =
> > PCI_BASE_ADDRESS_SPACE_MEMORY|PCI_BASE_ADDRESS_MEM_PREFETCH;
> > 
> > now we cannot anymore.
> > 
> 
> Will change to:
> -        if (r->type & XEN_HOST_PCI_REGION_TYPE_IO) {
> +        if (r->type & XEN_HOST_PCI_REGION_TYPE_IO)
>              type = PCI_BASE_ADDRESS_SPACE_IO;
> -        } else {
> +        else
>              type = PCI_BASE_ADDRESS_SPACE_MEMORY;
> -            if (r->type & XEN_HOST_PCI_REGION_TYPE_PREFETCH) {
> +            if (r->type & XEN_HOST_PCI_REGION_TYPE_MEM_64)
> +                type |= PCI_BASE_ADDRESS_MEM_TYPE_64;
> +           else if (r->type & XEN_HOST_PCI_REGION_TYPE_PREFETCH)
>                  type |= PCI_BASE_ADDRESS_MEM_PREFETCH;
> -            }
> -        }

Isn't it possible that both XEN_HOST_PCI_REGION_TYPE_MEM_64 and
XEN_HOST_PCI_REGION_TYPE_PREFETCH are set? It doesn't look like this can
cover that case.
The following seems to be what you are looking for:


if (r->type & XEN_HOST_PCI_REGION_TYPE_IO) {
    type = PCI_BASE_ADDRESS_SPACE_IO;
} else {
    type = PCI_BASE_ADDRESS_SPACE_MEMORY;
    if (r->type & XEN_HOST_PCI_REGION_TYPE_PREFETCH) {
        type |= PCI_BASE_ADDRESS_MEM_PREFETCH;
    }
    if (r->type & XEN_HOST_PCI_REGION_TYPE_MEM_64) {
        type |= PCI_BASE_ADDRESS_MEM_TYPE_64;
    }
}


> > >  static XenPTBarFlag xen_pt_bar_reg_parse(XenPCIPassthroughState *s,
> > >                                           XenPTRegInfo *reg)
> > >  {
> > > @@ -366,7 +367,7 @@ static XenPTBarFlag
> > xen_pt_bar_reg_parse(XenPCIPassthroughState *s,
> > >
> > >      /* check unused BAR */
> > >      r = &d->io_regions[index];
> > > -    if (r->size == 0) {
> > > +    if (!xen_pt_get_bar_size(r)) {
> > >          return XEN_PT_BAR_FLAG_UNUSED;
> > >      }
> > >
> > > @@ -383,6 +384,24 @@ static XenPTBarFlag
> > xen_pt_bar_reg_parse(XenPCIPassthroughState *s,
> > >      }
> > >  }
> > >
> > > +static bool is_64bit_bar(PCIIORegion *r)
> > > +{
> > > +    return !!(r->type & PCI_BASE_ADDRESS_MEM_TYPE_64);
> > > +}
> > > +
> > > +static uint64_t xen_pt_get_bar_size(PCIIORegion *r)
> > > +{
> > > +    if (is_64bit_bar(r))
> > > +    {
> > > +        uint64_t size64;
> > > +        size64 = (r + 1)->size;
> > > +        size64 <<= 32;
> > > +        size64 += r->size;
> > > +        return size64;
> > > +    }
> > > +    return r->size;
> > > +}
> > > +
> > >  static inline uint32_t base_address_with_flags(XenHostPCIIORegion *hr)
> > >  {
> > >      if (hr->type & XEN_HOST_PCI_REGION_TYPE_IO) {
> > > @@ -481,7 +500,10 @@ static int
> > xen_pt_bar_reg_write(XenPCIPassthroughState *s, XenPTReg *cfg_entry,
> > >      switch (s->bases[index].bar_flag) {
> > >      case XEN_PT_BAR_FLAG_MEM:
> > >          bar_emu_mask = XEN_PT_BAR_MEM_EMU_MASK;
> > > -        bar_ro_mask = XEN_PT_BAR_MEM_RO_MASK | (r_size - 1);
> > > +        if (!r_size)
> > > +            bar_ro_mask = XEN_PT_BAR_ALLF;
> > > +        else
> > > +            bar_ro_mask = XEN_PT_BAR_MEM_RO_MASK | (r_size - 1);
> > >          break;
> > 
> > Is this an actual mistake everywhere?
> 
> It's low 32bit mask for 64 bit bars.

I see. It is a good idea to add a line of comment in the code saying
that.

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