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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] x86/cpuid: Enable MSR_SPEC_CTRL in SVM guests by default
commit a7e7c7260cde78a148810db5320cbf39686c3e09
Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Jan 17 20:29:09 2022 +0000
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Feb 1 13:20:44 2022 +0000
x86/cpuid: Enable MSR_SPEC_CTRL in SVM guests by default
With all other pieces in place, MSR_SPEC_CTRL is fully working for HVM
guests.
Update the CPUID derivation logic (both PV and HVM to avoid losing subtle
changes), drop the MSR intercept, and explicitly enable the CPUID bits for
HVM
guests.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
xen/arch/x86/cpuid.c | 16 ++++++++++++----
xen/arch/x86/hvm/svm/svm.c | 4 ++++
xen/include/public/arch-x86/cpufeatureset.h | 16 ++++++++--------
xen/tools/gen-cpuid.py | 14 +++++++++-----
4 files changed, 33 insertions(+), 17 deletions(-)
diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index b5af48324a..e24dd283e7 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -433,6 +433,8 @@ static void __init
guest_common_feature_adjustments(uint32_t *fs)
*/
if ( test_bit(X86_FEATURE_IBRSB, fs) )
__set_bit(X86_FEATURE_STIBP, fs);
+ if ( test_bit(X86_FEATURE_IBRS, fs) )
+ __set_bit(X86_FEATURE_AMD_STIBP, fs);
/*
* On hardware which supports IBRS/IBPB, we can offer IBPB independently
@@ -456,11 +458,14 @@ static void __init calculate_pv_max_policy(void)
pv_featureset[i] &= pv_max_featuremask[i];
/*
- * If Xen isn't virtualising MSR_SPEC_CTRL for PV guests because of
- * administrator choice, hide the feature.
+ * If Xen isn't virtualising MSR_SPEC_CTRL for PV guests (functional
+ * availability, or admin choice), hide the feature.
*/
if ( !boot_cpu_has(X86_FEATURE_SC_MSR_PV) )
+ {
__clear_bit(X86_FEATURE_IBRSB, pv_featureset);
+ __clear_bit(X86_FEATURE_IBRS, pv_featureset);
+ }
guest_common_feature_adjustments(pv_featureset);
@@ -530,11 +535,14 @@ static void __init calculate_hvm_max_policy(void)
__set_bit(X86_FEATURE_SEP, hvm_featureset);
/*
- * If Xen isn't virtualising MSR_SPEC_CTRL for HVM guests because of
- * administrator choice, hide the feature.
+ * If Xen isn't virtualising MSR_SPEC_CTRL for HVM guests (functional
+ * availability, or admin choice), hide the feature.
*/
if ( !boot_cpu_has(X86_FEATURE_SC_MSR_HVM) )
+ {
__clear_bit(X86_FEATURE_IBRSB, hvm_featureset);
+ __clear_bit(X86_FEATURE_IBRS, hvm_featureset);
+ }
/*
* With VT-x, some features are only supported by Xen if dedicated
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 5459fbf4d4..c4ce3f75ab 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -606,6 +606,10 @@ static void svm_cpuid_policy_changed(struct vcpu *v)
vmcb_set_exception_intercepts(vmcb, bitmap);
+ /* Give access to MSR_SPEC_CTRL if the guest has been told about it. */
+ svm_intercept_msr(v, MSR_SPEC_CTRL,
+ cp->extd.ibrs ? MSR_INTERCEPT_NONE : MSR_INTERCEPT_RW);
+
/* Give access to MSR_PRED_CMD if the guest has been told about it. */
svm_intercept_msr(v, MSR_PRED_CMD,
cp->extd.ibpb ? MSR_INTERCEPT_NONE : MSR_INTERCEPT_RW);
diff --git a/xen/include/public/arch-x86/cpufeatureset.h
b/xen/include/public/arch-x86/cpufeatureset.h
index fd8ab25723..957df23b65 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -256,18 +256,18 @@ XEN_CPUFEATURE(CLZERO, 8*32+ 0) /*A CLZERO
instruction */
XEN_CPUFEATURE(RSTR_FP_ERR_PTRS, 8*32+ 2) /*A (F)X{SAVE,RSTOR} always
saves/restores FPU Error pointers */
XEN_CPUFEATURE(WBNOINVD, 8*32+ 9) /* WBNOINVD instruction */
XEN_CPUFEATURE(IBPB, 8*32+12) /*A IBPB support only (no IBRS, used
by AMD) */
-XEN_CPUFEATURE(IBRS, 8*32+14) /* MSR_SPEC_CTRL.IBRS */
-XEN_CPUFEATURE(AMD_STIBP, 8*32+15) /* MSR_SPEC_CTRL.STIBP */
-XEN_CPUFEATURE(IBRS_ALWAYS, 8*32+16) /* IBRS preferred always on */
-XEN_CPUFEATURE(STIBP_ALWAYS, 8*32+17) /* STIBP preferred always on */
-XEN_CPUFEATURE(IBRS_FAST, 8*32+18) /* IBRS preferred over software
options */
-XEN_CPUFEATURE(IBRS_SAME_MODE, 8*32+19) /* IBRS provides same-mode
protection */
+XEN_CPUFEATURE(IBRS, 8*32+14) /*S MSR_SPEC_CTRL.IBRS */
+XEN_CPUFEATURE(AMD_STIBP, 8*32+15) /*S MSR_SPEC_CTRL.STIBP */
+XEN_CPUFEATURE(IBRS_ALWAYS, 8*32+16) /*S IBRS preferred always on */
+XEN_CPUFEATURE(STIBP_ALWAYS, 8*32+17) /*S STIBP preferred always on */
+XEN_CPUFEATURE(IBRS_FAST, 8*32+18) /*S IBRS preferred over software
options */
+XEN_CPUFEATURE(IBRS_SAME_MODE, 8*32+19) /*S IBRS provides same-mode
protection */
XEN_CPUFEATURE(NO_LMSL, 8*32+20) /*S EFER.LMSLE no longer supported. */
XEN_CPUFEATURE(AMD_PPIN, 8*32+23) /* Protected Processor Inventory
Number */
-XEN_CPUFEATURE(AMD_SSBD, 8*32+24) /* MSR_SPEC_CTRL.SSBD available */
+XEN_CPUFEATURE(AMD_SSBD, 8*32+24) /*S MSR_SPEC_CTRL.SSBD available */
XEN_CPUFEATURE(VIRT_SSBD, 8*32+25) /* MSR_VIRT_SPEC_CTRL.SSBD */
XEN_CPUFEATURE(SSB_NO, 8*32+26) /*A Hardware not vulnerable to SSB */
-XEN_CPUFEATURE(PSFD, 8*32+28) /* MSR_SPEC_CTRL.PSFD */
+XEN_CPUFEATURE(PSFD, 8*32+28) /*S MSR_SPEC_CTRL.PSFD */
/* Intel-defined CPU features, CPUID level 0x00000007:0.edx, word 9 */
XEN_CPUFEATURE(AVX512_4VNNIW, 9*32+ 2) /*A AVX512 Neural Network Instructions
*/
diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index 470cd76d1c..39c8b0c774 100755
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -277,16 +277,20 @@ def crunch_numbers(state):
# The features:
# * Single Thread Indirect Branch Predictors
# * Speculative Store Bypass Disable
+ # * Predictive Store Forward Disable
#
- # enumerate new bits in MSR_SPEC_CTRL, which is enumerated by Indirect
- # Branch Restricted Speculation/Indirect Branch Prediction Barrier.
+ # enumerate new bits in MSR_SPEC_CTRL, and technically enumerate
+ # MSR_SPEC_CTRL itself. AMD further enumerates hints to guide OS
+ # behaviour.
#
- # In practice, these features also enumerate the presense of
- # MSR_SPEC_CTRL. However, no real hardware will exist with SSBD but
- # not IBRSB, and we pass this MSR directly to guests. Treating them
+ # However, no real hardware will exist with e.g. SSBD but not
+ # IBRSB/IBRS, and we pass this MSR directly to guests. Treating them
# as dependent features simplifies Xen's logic, and prevents the guest
# from seeing implausible configurations.
IBRSB: [STIBP, SSBD],
+ IBRS: [AMD_STIBP, AMD_SSBD, PSFD,
+ IBRS_ALWAYS, IBRS_FAST, IBRS_SAME_MODE],
+ AMD_STIBP: [STIBP_ALWAYS],
# In principle the TSXLDTRK insns could also be considered independent.
RTM: [TSXLDTRK],
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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