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SubjectRe: [PATCH] IR: Fix kernel hang if interrupt remapping disable in BIOS
On Wed, Sep 09, 2009 at 02:38:08PM -0700, Suresh Siddha wrote:
> On Wed, 2009-09-09 at 09:05 -0700, Song, Youquan wrote:
> > BIOS clear DMAR table INTR_REMAP flag to disable interrupt remapping. Current
> > kernel only check interrupt remapping(IR) flag in DRHD's extended capability
> > register to decide interrupt remapping support or not. But IR flag will not
> > change when BIOS disable/enable interrupt remapping.
> >
> > When user disable interrupt remapping in BIOS or BIOS often defaultly disable
> > interrupt remapping feature when BIOS is not mature.Though BIOS disable
> > interrupt remapping but intr_remapping_supported function will always report
> > to OS support interrupt remapping if VT-d2 chipset populated. On this
> > cases, kernel will continue enable interrupt remapping and result kernel panic.
> > This bug exist on almost all platforms with interrupt remapping support.
>
> I haven't encountered this before probably because bios was turning off
> the interrupt-remapping support in extended capability aswell. but I do
> agree that this fix is needed.
>
> >
> >
> > This patch add DMAR table INTR_REMAP flag check before enable interrup remapping
> >
> > Signed-off-by: Youquan Song <youquan.song@intel.com>
>
> Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
>
> David, Can you please pick this up?
>
> thanks.

David, Can you please pick this up? We want the bug fixed at 2.6.32.
Thanks.

>
> > ---
> >
> > diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
> > index a8a4383..d943e95 100644
> > --- a/drivers/pci/dmar.c
> > +++ b/drivers/pci/dmar.c
> > @@ -1302,3 +1302,13 @@ int dmar_reenable_qi(struct intel_iommu *iommu)
> >
> > return 0;
> > }
> > +
> > +/*
> > + * Check interrupt remapping support in DMAR table description.
> > + */
> > +int dmar_ir_support(void)
> > +{
> > + struct acpi_table_dmar *dmar;
> > + dmar = (struct acpi_table_dmar *)dmar_tbl;
> > + return dmar->flags & 0x1;
> > +}
> > diff --git a/drivers/pci/intr_remapping.c b/drivers/pci/intr_remapping.c
> > index ebfa47b..ac06514 100644
> > --- a/drivers/pci/intr_remapping.c
> > +++ b/drivers/pci/intr_remapping.c
> > @@ -611,6 +611,9 @@ int __init intr_remapping_supported(void)
> > if (disable_intremap)
> > return 0;
> >
> > + if (!dmar_ir_support())
> > + return 0;
> > +
> > for_each_drhd_unit(drhd) {
> > struct intel_iommu *iommu = drhd->iommu;
> >
> > diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> > index 482dc91..4f0a72a 100644
> > --- a/include/linux/intel-iommu.h
> > +++ b/include/linux/intel-iommu.h
> > @@ -360,4 +360,6 @@ extern void qi_flush_dev_iotlb(struct intel_iommu *iommu, u16 sid, u16 qdep,
> >
> > extern int qi_submit_sync(struct qi_desc *desc, struct intel_iommu *iommu);
> >
> > +extern int dmar_ir_support(void);
> > +
> > #endif
>
> --
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