[xen stable-4.16] x86/spec-ctrl: Expose IPRED_CTRL to guests

[patchbot@xxxxxxx]

commit c5d815f0dd830b24be8a088e286a166f79f8bb73
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Tue Jan 30 10:13:58 2024 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Apr 9 17:10:28 2024 +0100

    x86/spec-ctrl: Expose IPRED_CTRL to guests
    
    The CPUID feature bit signals the presence of the IPRED_DIS_{U,S} controls 
in
    SPEC_CTRL MSR, first available in Intel AlderLake and Sapphire Rapids CPUs.
    
    Xen already knows how to context switch MSR_SPEC_CTRL properly between guest
    and hypervisor context.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    (cherry picked from commit 4dd6760706848de30f7c8b5f83462b9bcb070c91)
---
 tools/misc/xen-cpuid.c                      | 2 +-
 xen/arch/x86/msr.c                          | 6 ++++--
 xen/include/asm-x86/msr-index.h             | 2 ++
 xen/include/public/arch-x86/cpufeatureset.h | 1 +
 xen/tools/gen-cpuid.py                      | 3 ++-
 5 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/misc/xen-cpuid.c b/tools/misc/xen-cpuid.c
index 0c792679e5..e59e17c722 100644
--- a/tools/misc/xen-cpuid.c
+++ b/tools/misc/xen-cpuid.c
@@ -212,7 +212,7 @@ static const char *const str_7d1[32] =
 
 static const char *const str_7d2[32] =
 {
-    [ 0] = "intel-psfd",
+    [ 0] = "intel-psfd",    [ 1] = "ipred-ctrl",
 };
 
 static const char *const str_m10Al[32] =
diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 22f86f2785..91b7402fba 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -306,8 +306,8 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
 
 /*
  * Caller to confirm that MSR_SPEC_CTRL is available.  Intel and AMD have
- * separate CPUID features for this functionality, but only set will be
- * active.
+ * separate CPUID features for some of this functionality, but only one
+ * vendors-worth will be active on a single host.
  */
 uint64_t msr_spec_ctrl_valid_bits(const struct cpu_policy *cp)
 {
@@ -321,6 +321,8 @@ uint64_t msr_spec_ctrl_valid_bits(const struct cpu_policy 
*cp)
     return (SPEC_CTRL_IBRS | SPEC_CTRL_STIBP |
             (ssbd       ? SPEC_CTRL_SSBD       : 0) |
             (psfd       ? SPEC_CTRL_PSFD       : 0) |
+            (cp->feat.ipred_ctrl
+             ? (SPEC_CTRL_IPRED_DIS_U | SPEC_CTRL_IPRED_DIS_S) : 0) |
             0);
 }
 
diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index eb6295d8a7..cab836c88f 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -36,6 +36,8 @@
 #define  SPEC_CTRL_IBRS                     (_AC(1, ULL) <<  0)
 #define  SPEC_CTRL_STIBP                    (_AC(1, ULL) <<  1)
 #define  SPEC_CTRL_SSBD                     (_AC(1, ULL) <<  2)
+#define  SPEC_CTRL_IPRED_DIS_U              (_AC(1, ULL) <<  3)
+#define  SPEC_CTRL_IPRED_DIS_S              (_AC(1, ULL) <<  4)
 #define  SPEC_CTRL_PSFD                     (_AC(1, ULL) <<  7)
 
 #define MSR_PRED_CMD                        0x00000049
diff --git a/xen/include/public/arch-x86/cpufeatureset.h 
b/xen/include/public/arch-x86/cpufeatureset.h
index 7a9d8d05d3..96601c5c20 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -307,6 +307,7 @@ XEN_CPUFEATURE(SRSO_NO,            11*32+29) /*A  Hardware 
not vulenrable to Spe
 
 /* Intel-defined CPU features, CPUID level 0x00000007:2.edx, word 13 */
 XEN_CPUFEATURE(INTEL_PSFD,         13*32+ 0) /*A  MSR_SPEC_CTRL.PSFD */
+XEN_CPUFEATURE(IPRED_CTRL,         13*32+ 1) /*A  MSR_SPEC_CTRL.IPRED_DIS_* */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:1.ecx, word 14 */
 
diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index 3ad9263221..f68e3ff875 100755
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -317,7 +317,8 @@ def crunch_numbers(state):
         # 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, INTEL_PSFD, EIBRS],
+        IBRSB: [STIBP, SSBD, INTEL_PSFD, EIBRS,
+                IPRED_CTRL],
         IBRS: [AMD_STIBP, AMD_SSBD, PSFD,
                IBRS_ALWAYS, IBRS_FAST, IBRS_SAME_MODE],
         IBPB: [IBPB_RET, SBPB, IBPB_BRTYPE],
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.16