Memory Protection eXtension support has been dropped from GCC and Linux, and
will be dropped from future Intel CPUs.
With all other default/max pieces in place, move MPX from default to max.
This means that VMs won't be offered it by default, but can explicitly opt
into using it via cpuid="host,mpx=1" in their vm.cfg file.
The difference as visible to the guest is:
diff --git a/default b/mpx
index 0e91765d6b..c8c33cd584 100644
--- a/default
+++ b/mpx
@@ -13,15 +13,17 @@ Native cpuid:
00000004:00000004 -> 00000000:00000000:00000000:00000000
00000005:ffffffff -> 00000000:00000000:00000000:00000000
00000006:ffffffff -> 00000000:00000000:00000000:00000000
- 00000007:00000000 -> 00000000:009c2fbb:00000000:9c000400
+ 00000007:00000000 -> 00000000:009c6fbb:00000000:9c000400
00000008:ffffffff -> 00000000:00000000:00000000:00000000
00000009:ffffffff -> 00000000:00000000:00000000:00000000
0000000a:ffffffff -> 00000000:00000000:00000000:00000000
0000000b:ffffffff -> 00000000:00000000:00000000:00000000
0000000c:ffffffff -> 00000000:00000000:00000000:00000000
- 0000000d:00000000 -> 00000007:00000240:00000340:00000000
+ 0000000d:00000000 -> 0000001f:00000240:00000440:00000000
0000000d:00000001 -> 0000000f:00000240:00000000:00000000
0000000d:00000002 -> 00000100:00000240:00000000:00000000
+ 0000000d:00000003 -> 00000040:000003c0:00000000:00000000
+ 0000000d:00000004 -> 00000040:00000400:00000000:00000000
40000000:ffffffff -> 40000005:566e6558:65584d4d:4d4d566e
40000001:ffffffff -> 0004000e:00000000:00000000:00000000
40000002:ffffffff -> 00000001:40000000:00000000:00000000
Adjust the legacy restore path in libxc to cope safely with pre-4.14 VMs.
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Wei Liu <w...@xen.org>
CC: Roger Pau Monné <roger....@citrix.com>
CC: Ian Jackson <ian.jack...@citrix.com>
CC: Wei Liu <w...@xen.org>
CC: Paul Durrant <p...@xen.org>
Dropped Jan's R-by from previous posting, as the patch has gained new
toolstack logic to avoid breaking migrate.
---
tools/libxc/xc_cpuid_x86.c | 48 ++++++++++++++++++-----------
xen/include/public/arch-x86/cpufeatureset.h | 2 +-
2 files changed, 31 insertions(+), 19 deletions(-)
diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index e017abffce..5649913e69 100644
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -436,6 +436,8 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t
domid, bool restore,
xen_cpuid_leaf_t *leaves = NULL;
struct cpuid_policy *p = NULL;
uint32_t err_leaf = -1, err_subleaf = -1, err_msr = -1;
+ uint32_t host_featureset[FEATURESET_NR_ENTRIES] = {};
+ uint32_t len = ARRAY_SIZE(host_featureset);
if ( xc_domain_getinfo(xch, domid, 1, &di) != 1 ||
di.domid != domid )
@@ -458,6 +460,22 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t
domid, bool restore,
(p = calloc(1, sizeof(*p))) == NULL )
goto out;
+ /* Get the host policy. */
+ rc = xc_get_cpu_featureset(xch, XEN_SYSCTL_cpu_featureset_host,
+ &len, host_featureset);
+ if ( rc )
+ {
+ /* Tolerate "buffer too small", as we've got the bits we need. */
+ if ( errno == ENOBUFS )
+ rc = 0;
+ else
+ {
+ PERROR("Failed to obtain host featureset");
+ rc = -errno;
+ goto out;
+ }
+ }
+
/* Get the domain's default policy. */
nr_msrs = 0;
rc = xc_get_system_cpu_policy(xch, di.hvm ?
XEN_SYSCTL_cpu_policy_hvm_default
@@ -479,6 +497,18 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t
domid, bool restore,
goto out;
}
+ /*
+ * Account for feature which have been disabled by default since Xen 4.13,
+ * so migrated-in VM's don't risk seeing features disappearing.
+ */
+ if ( restore )
+ {
+ if ( di.hvm )
+ {
+ p->feat.mpx = test_bit(X86_FEATURE_MPX, host_featureset);
+ }
+ }
+
if ( featureset )
{
uint32_t disabled_features[FEATURESET_NR_ENTRIES],
@@ -530,24 +560,6 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t
domid, bool restore,
if ( !di.hvm )
{
- uint32_t host_featureset[FEATURESET_NR_ENTRIES] = {};
- uint32_t len = ARRAY_SIZE(host_featureset);
-
- rc = xc_get_cpu_featureset(xch, XEN_SYSCTL_cpu_featureset_host,
- &len, host_featureset);
- if ( rc )
- {
- /* Tolerate "buffer too small", as we've got the bits we need. */
- if ( errno == ENOBUFS )
- rc = 0;
- else
- {
- PERROR("Failed to obtain host featureset");
- rc = -errno;
- goto out;
- }
- }
-
/*
* On hardware without CPUID Faulting, PV guests see real topology.
* As a consequence, they also need to see the host htt/cmp fields.
diff --git a/xen/include/public/arch-x86/cpufeatureset.h
b/xen/include/public/arch-x86/cpufeatureset.h
index 5ca35d9d97..af1b8a96a6 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -207,7 +207,7 @@ XEN_CPUFEATURE(INVPCID, 5*32+10) /*H Invalidate
Process Context ID */
XEN_CPUFEATURE(RTM, 5*32+11) /*A Restricted Transactional Memory */
XEN_CPUFEATURE(PQM, 5*32+12) /* Platform QoS Monitoring */
XEN_CPUFEATURE(NO_FPU_SEL, 5*32+13) /*! FPU CS/DS stored as zero */
-XEN_CPUFEATURE(MPX, 5*32+14) /*S Memory Protection Extensions */
+XEN_CPUFEATURE(MPX, 5*32+14) /*s Memory Protection Extensions */
XEN_CPUFEATURE(PQE, 5*32+15) /* Platform QoS Enforcement */
XEN_CPUFEATURE(AVX512F, 5*32+16) /*A AVX-512 Foundation Instructions */
XEN_CPUFEATURE(AVX512DQ, 5*32+17) /*A AVX-512 Doubleword & Quadword
Instrs */
--
2.11.0
