[Xen-changelog] [xen stable-4.8] IOMMU: default to always quarantining PCI devices

[patchbot@xxxxxxx]

commit ec6c25e4674880617747e0a6cd8e742004af7c08
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Nov 29 10:21:21 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Nov 29 10:21:21 2019 +0100

    IOMMU: default to always quarantining PCI devices
    
    XSA-302 relies on the use of libxl's "assignable-add" feature to prepare
    devices to be assigned to untrusted guests.
    
    Unfortunately, this is not considered a strictly required step for
    device assignment. The PCI passthrough documentation on the wiki
    describes alternate ways of preparing devices for assignment, and
    libvirt uses its own ways as well. Hosts where these alternate methods
    are used will still leave the system in a vulnerable state after the
    device comes back from a guest.
    
    Default to always quarantining PCI devices, but provide a command line
    option to revert back to prior behavior (such that people who both
    sufficiently trust their guests and want to be able to use devices in
    Dom0 again after they had been in use by a guest wouldn't need to
    "manually" move such devices back from DomIO to Dom0).
    
    This is XSA-306.
    
    Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Wei Liu <wl@xxxxxxx>
---
 docs/misc/xen-command-line.markdown | 11 ++++++++++-
 xen/drivers/passthrough/iommu.c     |  3 +++
 xen/drivers/passthrough/pci.c       |  3 ++-
 xen/include/xen/iommu.h             |  2 +-
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index 6db0daf533..74fc38b43f 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1029,7 +1029,7 @@ debug hypervisor only).
 > Default: `new` unless directed-EOI is supported
 
 ### iommu
-> `= List of [ <boolean> | force | required | intremap | intpost | qinval | 
snoop | sharept | dom0-passthrough | dom0-strict | amd-iommu-perdev-intremap | 
workaround_bios_bug | igfx | verbose | debug ]`
+> `= List of [ <boolean> | force | required | quarantine | intremap | intpost 
| qinval | snoop | sharept | dom0-passthrough | dom0-strict | 
amd-iommu-perdev-intremap | workaround_bios_bug | igfx | verbose | debug ]`
 
 > Sub-options:
 
@@ -1049,6 +1049,15 @@ debug hypervisor only).
 >> Don't continue booting unless IOMMU support is found and can be initialized
 >> successfully.
 
+> `quarantine`
+
+> Default: `true`
+
+>> Control Xen's behavior when de-assigning devices from guests.  If enabled,
+>> Xen always quarantines such devices; they must be explicitly assigned back
+>> to Dom0 before they can be used there again.  If disabled, Xen will only
+>> quarantine devices the toolstack hass arranged for getting quarantined.
+
 > `intremap`
 
 > Default: `true`
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 9ebb8c6bc4..0d3941f244 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -52,6 +52,7 @@ custom_param("iommu", parse_iommu_param);
 bool_t __initdata iommu_enable = 1;
 bool_t __read_mostly iommu_enabled;
 bool_t __read_mostly force_iommu;
+bool __read_mostly iommu_quarantine = true;
 bool_t __hwdom_initdata iommu_dom0_strict;
 bool_t __read_mostly iommu_verbose;
 bool_t __read_mostly iommu_workaround_bios_bug;
@@ -96,6 +97,8 @@ static void __init parse_iommu_param(char *s)
             iommu_enable = 0;
         else if ( !strcmp(s, "force") || !strcmp(s, "required") )
             force_iommu = val;
+        else if ( !strcmp(s, "quarantine") )
+            iommu_quarantine = val;
         else if ( !strcmp(s, "workaround_bios_bug") )
             iommu_workaround_bios_bug = val;
         else if ( !strcmp(s, "igfx") )
diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index ef3d39c65b..0b9f0261ab 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -1460,7 +1460,8 @@ int deassign_device(struct domain *d, u16 seg, u8 bus, u8 
devfn)
         return -ENODEV;
 
     /* De-assignment from dom_io should de-quarantine the device */
-    target = (pdev->quarantine && pdev->domain != dom_io) ?
+    target = ((pdev->quarantine || iommu_quarantine) &&
+              pdev->domain != dom_io) ?
         dom_io : hardware_domain;
 
     while ( pdev->phantom_stride )
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index 5803e3f95b..5f9f82ea22 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -28,7 +28,7 @@
 #include <asm/iommu.h>
 
 extern bool_t iommu_enable, iommu_enabled;
-extern bool_t force_iommu, iommu_verbose;
+extern bool force_iommu, iommu_quarantine, iommu_verbose;
 extern bool_t iommu_workaround_bios_bug, iommu_igfx, iommu_passthrough;
 extern bool_t iommu_snoop, iommu_qinval, iommu_intremap, iommu_intpost;
 extern bool_t iommu_hap_pt_share;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8

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