On Tue, May 20, 2014 at 05:13:45AM +0000, Chen, Tiejun wrote: > > -----Original Message----- > > From: Konrad Rzeszutek Wilk [mailto:konrad.w...@oracle.com] > > Sent: Monday, May 19, 2014 9:34 PM > > To: Zhang, Yang Z > > Cc: Chen, Tiejun; anthony.per...@citrix.com; > > stefano.stabell...@eu.citrix.com; > > m...@redhat.com; kelly.zyta...@amd.com; peter.mayd...@linaro.org; > > xen-de...@lists.xensource.com; weidong....@intel.com; Kay, Allen M; > > qemu-devel@nongnu.org; jean.guya...@eu.citrix.com; > > anth...@codemonkey.ws > > Subject: Re: [Xen-devel] [v2][PATCH 6/8] xen, gfx passthrough: support Intel > > IGD passthrough with VT-D > > > > On Mon, May 19, 2014 at 12:58:50AM +0000, Zhang, Yang Z wrote: > > > Konrad Rzeszutek Wilk wrote on 2014-05-16: > > > > On Fri, May 16, 2014 at 06:53:42PM +0800, Tiejun Chen wrote: > > > > > Some registers of Intel IGD are mapped in host bridge, so it needs > > > > > to passthrough these registers of physical host bridge to guest > > > > > because emulated host bridge in guest doesn't have these mappings. > > > > > > Thanks for your review for the whole series patch. > > > > Sure thing! > > > > .. snip.. > > > > > +write_default: > > > > > + pci_default_write_config(pci_dev, config_addr, val, len); > > > > > > > > > > > > and we just allow it through. But what happens if the guest decides > > > > to change the BAR sizes? Or fiddle with the GTT? > > > > > > > > Ouch. That really looks dangerous - or maybe I am too paranoid? > > > > > > > > > > I do not quite understand your concern. We only pass through PAVPC to > > physical host bridge. The others are handled by current logic. We don't > > change > > any of it. So what problem will be exposed by this patch? > > > > Ah, I assumed that pci_default_write_config would be writting everything > > without any checks. But it looks to be doing the right thing and just sets > > the > > emulated values. > > > > Could we just add comment saying that it writes to the emulated values? That > > way it won't trip folks. > > diff --git a/hw/xen/xen_pt_graphics.c b/hw/xen/xen_pt_graphics.c > index 1342f4f..5e5e3d5 100644 > --- a/hw/xen/xen_pt_graphics.c > +++ b/hw/xen/xen_pt_graphics.c > @@ -367,6 +367,7 @@ void igd_pci_write(PCIDevice *pci_dev, uint32_t > config_addr, > case 0x58: /* PAVPC Offset */ > break; > default: > + /* Just sets the emulated values. */ > goto write_default; > } > > @@ -427,6 +428,7 @@ uint32_t igd_pci_read(PCIDevice *pci_dev, uint32_t > config_addr, int len) > case 0xa8: /* SNB: base of GTT stolen memory */ > break; > default: > + /* Just gets the emulated values. */ > goto read_default;
Thanks! > } > > Thanks > Tiejun
