File xsa456-0c.patch of Package xen.33138

# Commit 583f1d0950529f3517b1741c2b21a028a82ba831
# Date 2024-02-01 19:52:44 +0000
# Author Roger Pau Monné <roger.pau@citrix.com>
# Committer Andrew Cooper <andrew.cooper3@citrix.com>
x86/spec-ctrl: Expose BHI_CTRL to guests

The CPUID feature bit signals the presence of the BHI_DIS_S control 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@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -253,6 +253,7 @@ uint64_t msr_spec_ctrl_valid_bits(const
              ? (SPEC_CTRL_IPRED_DIS_U | SPEC_CTRL_IPRED_DIS_S) : 0) |
             (cp->feat.rrsba_ctrl
              ? (SPEC_CTRL_RRSBA_DIS_U | SPEC_CTRL_RRSBA_DIS_S) : 0) |
+            (cp->feat.bhi_ctrl   ? SPEC_CTRL_BHI_DIS_S : 0) |
             0);
 }
 
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -46,6 +46,7 @@
 #define SPEC_CTRL_RRSBA_DIS_U		(_AC(1, ULL) << 5)
 #define SPEC_CTRL_RRSBA_DIS_S		(_AC(1, ULL) << 6)
 #define SPEC_CTRL_PSFD			(_AC(1, ULL) << 7)
+#define SPEC_CTRL_BHI_DIS_S		(_AC(1, ULL) << 10)
 
 #define MSR_PRED_CMD			0x00000049
 #define PRED_CMD_IBPB			(_AC(1, ULL) << 0)
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -291,6 +291,7 @@ XEN_CPUFEATURE(INTEL_PSFD,         13*32
 XEN_CPUFEATURE(IPRED_CTRL,         13*32+ 1) /*A  MSR_SPEC_CTRL.IPRED_DIS_* */
 XEN_CPUFEATURE(RRSBA_CTRL,         13*32+ 2) /*A  MSR_SPEC_CTRL.RRSBA_DIS_* */
 XEN_CPUFEATURE(DDP_CTRL,           13*32+ 3) /*   MSR_SPEC_CTRL.DDP_DIS_U */
+XEN_CPUFEATURE(BHI_CTRL,           13*32+ 4) /*A  MSR_SPEC_CTRL.BHI_DIS_S */
 XEN_CPUFEATURE(MCDT_NO,            13*32+ 5) /*A  MCDT_NO */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:1.ecx, word 14 */
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -307,7 +307,7 @@ def crunch_numbers(state):
         # as dependent features simplifies Xen's logic, and prevents the guest
         # from seeing implausible configurations.
         IBRSB: [STIBP, SSBD, INTEL_PSFD, EIBRS,
-                IPRED_CTRL, RRSBA_CTRL],
+                IPRED_CTRL, RRSBA_CTRL, BHI_CTRL],
         IBPB: [IBPB_RET, SBPB, IBPB_BRTYPE],
 
         # The ARCH_CAPS CPUID bit enumerates the availability of the whole register.