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[Xen-devel] [PATCH 2/2] xen/swiotlb: If user supplied e820_hole=1 in the guest config, enable SWIOTLB.

We can detect that the user is using e820_hole=1 by parsing the E820.
If it shows regions other than E820_RAM or E820_RESV then the
user is bent on providing us with a PCI device and forgot
to do 'iommu=soft'. So lets enable it for him/her.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
 arch/x86/xen/pci-swiotlb-xen.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
index 56f373e..9b1aebb 100644
--- a/arch/x86/xen/pci-swiotlb-xen.c
+++ b/arch/x86/xen/pci-swiotlb-xen.c
@@ -74,6 +74,11 @@ int __init pci_xen_swiotlb_detect(void)
        if (xen_pv_domain())
                swiotlb = 0;
+       /* If it hasn't been activated yet, and it has E820 that looks like
+        * the user supplied e820_hole=1, then turn it on. */
+       if (xen_pv_domain() && !xen_initial_domain() &&
+           !xen_swiotlb && e820_has_acpi())
+               xen_swiotlb = 1;
        return xen_swiotlb;

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