[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RFC 4/4] xen/pvhvm: Make MSI IRQs work after kexec
On Tue, Jul 15, 2014 at 03:40:40PM +0200, Vitaly Kuznetsov wrote: > When kexec was peformed MSI IRQs for passthrough-ed devices were already > mapped and we see non-zero pirq extracted from MSI msg. xen_irq_from_pirq() > fails as we have no IRQ mapping information for that. Requesting for new > mapping with __write_msi_msg() does not result in MSI IRQ being remapped so > we don't recieve these IRQs. receive How come '__write_msi_msg' does not result in new MSI IRQs? Is it fair to state that your code ends up reading the MSI IRQ (PIRQ) from the device and updating the internal PIRQ<->IRQ code to match with the reality? > > RFC: I wasn't able to understand why commit af42b8d1 which introduced > xen_irq_from_pirq() check in xen_hvm_setup_msi_irqs() is checking that instead > of checking pirq > 0 as if the mapping was already done (and we have pirq>0 > here) > we don't need to request for a new pirq. We're loosing existing PIRQ and I'm > also > not sure when __write_msi_msg() with new PIRQ will result in new mapping. We don't request a new pirq. We end up returning before we call xen_allocate_pirq_msi. At least that is how the commit you mentioned worked. In regards to why using 'xen_irq_from_pirq' instead of just checking the PIRQ - is that we might be called twice by a buggy driver. As such we want to check our PIRQ<->IRQ to figure this out. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > --- > arch/x86/pci/xen.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c > index 905956f..685e8f1 100644 > --- a/arch/x86/pci/xen.c > +++ b/arch/x86/pci/xen.c > @@ -231,8 +231,7 @@ static int xen_hvm_setup_msi_irqs(struct pci_dev *dev, > int nvec, int type) > __read_msi_msg(msidesc, &msg); > pirq = MSI_ADDR_EXT_DEST_ID(msg.address_hi) | > ((msg.address_lo >> MSI_ADDR_DEST_ID_SHIFT) & 0xff); > - if (msg.data != XEN_PIRQ_MSI_DATA || > - xen_irq_from_pirq(pirq) < 0) { > + if (msg.data != XEN_PIRQ_MSI_DATA || pirq <= 0) { > pirq = xen_allocate_pirq_msi(dev, msidesc); > if (pirq < 0) { > irq = -ENODEV; > -- > 1.9.3 > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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