I implemented a patch for it. Noboru, pls have a try on your machine.
If you use default iommu=1, VT-d will be disabled with warning messages.
If you use iommu=workaround_bios_bug, it should enable VT-d and works
for you.
If you use iommu=force, it panics.
patch title: VT-d: add "iommu=workaround_bios_bug" option
patch description:
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>
Regards,
Weidong
Noboru Iwamatsu wrote:
Weidong, Keir,
I agree your suggestions.
Noboru.
Keir Fraser wrote:
On 25/01/2010 10:45, "Sander Eikelenboom" <linux@xxxxxxxxxxxxxx> wrote:
a) Could be discussed if panic should be default instead of disabling
iommu or
not, although there seem to be a lot of broken bioses, so that would
lead to a
lot of machines not booting.
Absolutely not acceptable. Warn and completely disable IOMMU is the
correct
default causing least pain to the most end users.
-- Keir
Agree. It should not crash Xen by default due to BIOS issues.
warn-and-disable is better. It won't impact common Xen users, and if a
user really wants to use VT-d, he can try iommu=workaround_bogus_bios,
or directly report to OEM vendor to get it fixed in BIOS. As VT-d is
used more and more widely, I think the BIOS issues will be found and
fixed more quickly than before, thus the situation should be better.
Regards,
Weidong
diff -r 5dabbf2826c5 xen/drivers/passthrough/iommu.c
--- a/xen/drivers/passthrough/iommu.c Mon Jan 25 09:58:53 2010 +0800
+++ b/xen/drivers/passthrough/iommu.c Tue Jan 26 21:17:46 2010 +0800
@@ -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 5dabbf2826c5 xen/drivers/passthrough/vtd/dmar.c
--- a/xen/drivers/passthrough/vtd/dmar.c Mon Jan 25 09:58:53 2010 +0800
+++ b/xen/drivers/passthrough/vtd/dmar.c Tue Jan 26 21:16:49 2010 +0800
@@ -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 5dabbf2826c5 xen/include/xen/iommu.h
--- a/xen/include/xen/iommu.h Mon Jan 25 09:58:53 2010 +0800
+++ b/xen/include/xen/iommu.h Tue Jan 26 21:17:08 2010 +0800
@@ -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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