On Sat, Oct 27, 2007 at 02:19:38AM +0200, Muli Ben-Yehuda wrote:
> On Fri, Oct 26, 2007 at 11:18:49AM -0700, Mark Gross wrote:
>
> > The following patch clears the portect memory region enable bit at
> > boot time by default. It also provides a kernel parrameter for
> > disabling this behavior and leave the PMEN_REG untouched if so
> > wanted.
> >
> > If the boot loader or platform has protected memory regions enabled
> > at boot time it could prevent DMA's from happening as drivers are
> > loaded and used.
>
> What's the value of adding a command line option for this? Under what
> circumstances would we want to not clear this bit?
umm, /me asks around and finds out that at this time there isn't much
point to having a command line to preserve any protected areas set up at
boot time.
>
> > + } else if (!strncmp(str, "no_epm_clear", 12)) {
> > + printk(KERN_INFO
> > + "Intel-IOMMU: subress clearing of Enable "
> > + "Protected Memory bit\n");
> > + clear_pmen_epm = 0;
>
> `suppress', I assume. Rest looks fine, if the configuration option is
> really needed.
>
> Cheers,
> Muli
> --
> SYSTOR 2007 --- 1st Annual Haifa Systems and Storage Conference 2007
> http://www.haifa.il.ibm.com/Workshops/systor2007/
>
> Virtualization workshop: Oct 29th, 2007 | Storage workshop: Oct 30th, 2007
> -
Signed-off-by: mark gross <[email protected]>
--mgross
Index: linux-2.6/drivers/pci/intel-iommu.c
===================================================================
--- linux-2.6.orig/drivers/pci/intel-iommu.c 2007-10-24 09:31:32.000000000 -0700
+++ linux-2.6/drivers/pci/intel-iommu.c 2007-10-29 13:30:29.000000000 -0700
@@ -692,6 +692,23 @@
DMA_TLB_PSI_FLUSH, non_present_entry_flush);
}
+static void iommu_disable_protect_mem_regions(struct intel_iommu *iommu)
+{
+ u32 pmen;
+ unsigned long flags;
+
+ spin_lock_irqsave(&iommu->register_lock, flags);
+ pmen = readl(iommu->reg + DMAR_PMEN_REG);
+ pmen &= ~DMA_PMEN_EPM;
+ writel(pmen, iommu->reg + DMAR_PMEN_REG);
+
+ /* wait for the protected region status bit to clear */
+ IOMMU_WAIT_OP(iommu, DMAR_PMEN_REG,
+ readl, (pmen & DMA_PMEN_PRS), pmen);
+
+ spin_unlock_irqrestore(&iommu->register_lock, flags);
+}
+
static int iommu_enable_translation(struct intel_iommu *iommu)
{
u32 sts;
@@ -1731,6 +1748,8 @@
iommu_flush_context_global(iommu, 0);
iommu_flush_iotlb_global(iommu, 0);
+ iommu_disable_protect_mem_regions(iommu);
+
ret = iommu_enable_translation(iommu);
if (ret)
goto error;
Index: linux-2.6/drivers/pci/intel-iommu.h
===================================================================
--- linux-2.6.orig/drivers/pci/intel-iommu.h 2007-10-24 09:31:32.000000000 -0700
+++ linux-2.6/drivers/pci/intel-iommu.h 2007-10-29 10:30:24.000000000 -0700
@@ -126,6 +126,10 @@
#define DMA_TLB_IH_NONLEAF (((u64)1) << 6)
#define DMA_TLB_MAX_SIZE (0x3f)
+/* PMEN_REG */
+#define DMA_PMEN_EPM (((u32)1)<<31)
+#define DMA_PMEN_PRS (((u32)1)<<0)
+
/* GCMD_REG */
#define DMA_GCMD_TE (((u32)1) << 31)
#define DMA_GCMD_SRTP (((u32)1) << 30)
-
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