x86/spec-ctrl: Support Intel PSFD for guests

The Feb 2022 microcode from Intel retrofits AMD's MSR_SPEC_CTRL.PSFD interface
to Sunny Cove (IceLake) and later cores.

Update the MSR_SPEC_CTRL emulation, and expose it to guests.

Signed-off-by: Andrew Cooper <[email protected]>
Reviewed-by: Jan Beulich <[email protected]>
(cherry picked from commit 52ce1c9)

Author: andyhhp

tools/libs/light/libxl_cpuid.c

@@ -234,6 +234,8 @@ int libxl_cpuid_parse_config(libxl_cpuid_policy_list *cpuid, const char* str)
         {"fsrs",         0x00000007,  1, CPUID_REG_EAX, 11,  1},
         {"fsrcs",        0x00000007,  1, CPUID_REG_EAX, 12,  1},
 
+        {"intel-psfd",   0x00000007,  2, CPUID_REG_EDX,  0,  1},
+
         {"lahfsahf",     0x80000001, NA, CPUID_REG_ECX,  0,  1},
         {"cmplegacy",    0x80000001, NA, CPUID_REG_ECX,  1,  1},
         {"svm",          0x80000001, NA, CPUID_REG_ECX,  2,  1},

tools/misc/xen-cpuid.c

@@ -199,6 +199,7 @@ static const char *const str_7b1[32] =
 
 static const char *const str_7d2[32] =
 {
+    [ 0] = "intel-psfd",
 };
 
 static const struct {

xen/arch/x86/msr.c

@@ -443,7 +443,7 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
 uint64_t msr_spec_ctrl_valid_bits(const struct cpuid_policy *cp)
 {
     bool ssbd = cp->feat.ssbd || cp->extd.amd_ssbd;
-    bool psfd = cp->extd.psfd;
+    bool psfd = cp->feat.intel_psfd || cp->extd.psfd;
 
     /*
      * Note: SPEC_CTRL_STIBP is specified as safe to use (i.e. ignored)

xen/arch/x86/spec_ctrl.c

@@ -307,11 +307,13 @@ custom_param("pv-l1tf", parse_pv_l1tf);
 
 static void __init print_details(enum ind_thunk thunk, uint64_t caps)
 {
-    unsigned int _7d0 = 0, e8b = 0, tmp;
+    unsigned int _7d0 = 0, _7d2 = 0, e8b = 0, max = 0, tmp;
 
     /* Collect diagnostics about available mitigations. */
     if ( boot_cpu_data.cpuid_level >= 7 )
-        cpuid_count(7, 0, &tmp, &tmp, &tmp, &_7d0);
+        cpuid_count(7, 0, &max, &tmp, &tmp, &_7d0);
+    if ( max >= 2 )
+        cpuid_count(7, 2, &tmp, &tmp, &tmp, &_7d2);
     if ( boot_cpu_data.extended_cpuid_level >= 0x80000008 )
         cpuid(0x80000008, &tmp, &e8b, &tmp, &tmp);
 
@@ -345,6 +347,7 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps)
            (_7d0 & cpufeat_mask(X86_FEATURE_STIBP))          ? " STIBP"          : "",
            (e8b  & cpufeat_mask(X86_FEATURE_AMD_SSBD)) ||
            (_7d0 & cpufeat_mask(X86_FEATURE_SSBD))           ? " SSBD"           : "",
+           (_7d2 & cpufeat_mask(X86_FEATURE_INTEL_PSFD)) ||
            (e8b  & cpufeat_mask(X86_FEATURE_PSFD))           ? " PSFD"           : "",
            (_7d0 & cpufeat_mask(X86_FEATURE_L1D_FLUSH))      ? " L1D_FLUSH"      : "",
            (_7d0 & cpufeat_mask(X86_FEATURE_MD_CLEAR))       ? " MD_CLEAR"       : "",

xen/include/public/arch-x86/cpufeatureset.h

@@ -300,6 +300,7 @@ XEN_CPUFEATURE(NSCB,               11*32+ 6) /*A  Null Selector Clears Base (and
 /* Intel-defined CPU features, CPUID level 0x00000007:1.ebx, word 12 */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:2.edx, word 13 */
+XEN_CPUFEATURE(INTEL_PSFD,         13*32+ 0) /*A  MSR_SPEC_CTRL.PSFD */
 
 #endif /* XEN_CPUFEATURE */
 

xen/tools/gen-cpuid.py

@@ -287,7 +287,7 @@ 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],
+        IBRSB: [STIBP, SSBD, INTEL_PSFD],
         IBRS: [AMD_STIBP, AMD_SSBD, PSFD,
                IBRS_ALWAYS, IBRS_FAST, IBRS_SAME_MODE],
         AMD_STIBP: [STIBP_ALWAYS],