Re: [Xen-devel] [PATCH] qemu-xen-trad/pt_msi_disable: do not clear all MSI flags

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 10 Dec 2012, Sander Eikelenboom wrote:
> Monday, December 10, 2012, 1:36:41 PM, you wrote:
> 
> > "qemu-xen-trad: fix msi_translate with PV event delivery" added a
> > pt_msi_disable() call into pt_msgctrl_reg_write, clearing the MSI flags
> > as a consequence. MSIs get enabled again soon after by calling
> > pt_msi_setup.
> 
> > However the MSI flags are only setup once inÂthe pt_msgctrl_reg_init
> > function, so from the QEMU point of view the device has lost some
> > important properties, like for example PCI_MSI_FLAGS_64BIT.
> 
> > This patch fixes the bug by clearing only the MSI
> > enabled/mapped/initialized flags in pt_msi_disable.
> 
> 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > Tested-by: G.R. <firemeteor@xxxxxxxxxxxxxxxxxxxxx>
> > Xen-devel: http://marc.info/?l=xen-devel&m=135489879503075
> 
> > diff --git a/hw/pt-msi.c b/hw/pt-msi.c
> > index 73f737d..b03b989 100644
> > --- a/hw/pt-msi.c
> > +++ b/hw/pt-msi.c
> > @@ -213,7 +213,7 @@ void pt_msi_disable(struct pt_dev *dev)
> >  
> >  out:
> >      /* clear msi info */
> -    dev->>msi->flags = 0;
> +    dev->>msi->flags &= ~(MSI_FLAG_UNINIT | PT_MSI_MAPPED | 
> PCI_MSI_FLAGS_ENABLE);
> >      dev->msi->pirq = -1;
> >      dev->msi_trans_en = 0;
> >  }
> 
> 
> Seems this should be fixed for qemu-upstream as well ?
> I think since switching to qemu-upstream as default for xen-unstable / 4.3 
> seems around the corner,
> it's perhaps wise for all patches to qemu-traditional, to also check if 
> qemu-upstream needs the same fix (to prevent regressions after the switch) ?
> 

That is true and you do right to remind me, but this is one of the few
cases of PCI passthrough code where upstream QEMU and
qemu-xen-traditional differ: MSI translation is not implemented at all
in upstream QEMU so there is no need for this patch there.

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