# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1264492280 0
# Node ID 9ec971345d9f8d5064b5166cd2280b4707763912
# Parent 23a2ae169779e9fc29b93d5191c57a07b8399b08
VT-d: add "iommu=workaround_bios_bug" option
Add this option to workaround BIOS bugs. Currently it ignores DRHD
if "all" devices under its scope are not pci discoverable. This
workarounds a BIOS bug in some platforms to make VT-d work. But note
that this option doesn't guarantee security, because it might ignore
DRHD.
So there are 3 options which handle BIOS bugs differently:
iommu=1 (default): If detect non-existent device under a DRHD's
scope, or find incorrect RMRR setting (base_address > end_address),
disable VT-d completely in Xen with warning messages. This guarantees
security when VT-d enabled, or just disable VT-d to let Xen work
without VT-d.
iommu=force: it enforces to enable VT-d in Xen. If VT-d cannot be
enabled, it will crashes Xen. This is mainly for users who must need
VT-d.
iommu=workaround_bogus_bios: it workarounds some BIOS bugs to make
VT-d still work. This might be insecure because there might be a
device not protected by any DRHD if the device is re-enabled by
malicious s/w. This is for users who want to use VT-d regardless of
security.
Signed-off-by: Weidong Han <weidong.han@xxxxxxxxx>
---
xen/drivers/passthrough/iommu.c | 5 +++++
xen/drivers/passthrough/vtd/dmar.c | 14 +++++++++-----
xen/include/xen/iommu.h | 1 +
3 files changed, 15 insertions(+), 5 deletions(-)
diff -r 23a2ae169779 -r 9ec971345d9f xen/drivers/passthrough/iommu.c
--- a/xen/drivers/passthrough/iommu.c Tue Jan 26 07:50:04 2010 +0000
+++ b/xen/drivers/passthrough/iommu.c Tue Jan 26 07:51:20 2010 +0000
@@ -30,6 +30,8 @@ static int iommu_populate_page_table(str
* pv Enable IOMMU for PV domains
* no-pv Disable IOMMU for PV domains (default)
* force|required Don't boot unless IOMMU is enabled
+ * workaround_bios_bug Workaround some bios issue to still enable
+ VT-d, don't guarantee security
* passthrough Enable VT-d DMA passthrough (no DMA
* translation for Dom0)
* no-snoop Disable VT-d Snoop Control
@@ -40,6 +42,7 @@ int iommu_enabled = 1;
int iommu_enabled = 1;
int iommu_pv_enabled;
int force_iommu;
+int iommu_workaround_bios_bug;
int iommu_passthrough;
int iommu_snoop = 1;
int iommu_qinval = 1;
@@ -65,6 +68,8 @@ static void __init parse_iommu_param(cha
iommu_pv_enabled = 0;
else if ( !strcmp(s, "force") || !strcmp(s, "required") )
force_iommu = 1;
+ else if ( !strcmp(s, "workaround_bios_bug") )
+ iommu_workaround_bios_bug = 1;
else if ( !strcmp(s, "passthrough") )
iommu_passthrough = 1;
else if ( !strcmp(s, "no-snoop") )
diff -r 23a2ae169779 -r 9ec971345d9f xen/drivers/passthrough/vtd/dmar.c
--- a/xen/drivers/passthrough/vtd/dmar.c Tue Jan 26 07:50:04 2010 +0000
+++ b/xen/drivers/passthrough/vtd/dmar.c Tue Jan 26 07:51:20 2010 +0000
@@ -421,17 +421,21 @@ acpi_parse_one_drhd(struct acpi_dmar_ent
if ( invalid_cnt )
{
xfree(dmaru);
- if ( invalid_cnt == dmaru->scope.devices_cnt )
+
+ if ( iommu_workaround_bios_bug &&
+ invalid_cnt == dmaru->scope.devices_cnt )
{
dprintk(XENLOG_WARNING VTDPREFIX,
- " Ignore the DRHD due to all devices under "
- "its scope are not PCI discoverable!\n");
+ " Workaround BIOS bug: ignore the DRHD due to all "
+ "devices under its scope are not PCI discoverable!\n");
}
else
{
dprintk(XENLOG_WARNING VTDPREFIX,
- " The DRHD is invalid due to some devices under "
- "its scope are not PCI discoverable!\n");
+ " The DRHD is invalid due to there are devices under "
+ "its scope are not PCI discoverable! Pls try option "
+ "iommu=force or iommu=workaround_bios_bug if you "
+ "really want VT-d\n");
ret = -EINVAL;
}
}
diff -r 23a2ae169779 -r 9ec971345d9f xen/include/xen/iommu.h
--- a/xen/include/xen/iommu.h Tue Jan 26 07:50:04 2010 +0000
+++ b/xen/include/xen/iommu.h Tue Jan 26 07:51:20 2010 +0000
@@ -29,6 +29,7 @@ extern int iommu_enabled;
extern int iommu_enabled;
extern int iommu_pv_enabled;
extern int force_iommu;
+extern int iommu_workaround_bios_bug;
extern int iommu_passthrough;
extern int iommu_snoop;
extern int iommu_qinval;
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