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>
(cherry picked from commit 583f1d0950529f3517b1741c2b21a028a82ba831)

diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 615314f1e1ae45e69dd857ffc37fba0f2f86445f..51e6744e8f48145bcf49f972cb25749c6906588d 100644 (file)
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -335,6 +335,7 @@ uint64_t msr_spec_ctrl_valid_bits(const struct cpu_policy *cp)
              ? (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);
 }
 

diff --git a/xen/include/public/arch-x86/cpufeatureset.h b/xen/include/public/arch-x86/cpufeatureset.h
index 0e1581cdac230408253d7f746527bf02c5bd6881..51f238683c241a7fe271bad21e0b8c706047335a 100644 (file)
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -297,7 +297,7 @@ XEN_CPUFEATURE(INTEL_PPIN,         12*32+ 0) /*   Protected Processor Inventory
 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_* */
 XEN_CPUFEATURE(RRSBA_CTRL,         13*32+ 2) /*A  MSR_SPEC_CTRL.RRSBA_DIS_* */
-XEN_CPUFEATURE(BHI_CTRL,           13*32+ 4) /*   MSR_SPEC_CTRL.BHI_DIS_S */
+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 */

diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index 09acb9764c9fc21190a52587311a7c954b8ba270..a7c2ba3e5d79e275e46d24b6ba50614e0bdd7ac4 100755 (executable)
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -319,7 +319,7 @@ 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],
         IBRS: [AMD_STIBP, AMD_SSBD, PSFD,
                IBRS_ALWAYS, IBRS_FAST, IBRS_SAME_MODE],
         IBPB: [IBPB_RET, SBPB, IBPB_BRTYPE],