[xen master] x86: Begin to introduce support for MSR_ARCH_CAPS

[patchbot@xxxxxxx]

commit e32605b07ef2e01c9d05da9b2d5d7b8f9a5c7c1b
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Apr 10 16:25:40 2018 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Aug 27 12:48:46 2020 +0100

    x86: Begin to introduce support for MSR_ARCH_CAPS
    
    ... including serialisation/deserialisation logic and unit tests.
    
    There is no current way to configure this MSR correctly for guests.
    The toolstack side this logic needs building, which is far easier to
    do with it in place.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 tools/tests/cpu-policy/test-cpu-policy.c    |  5 +++++
 xen/arch/x86/msr.c                          |  6 ++++--
 xen/include/public/arch-x86/cpufeatureset.h |  2 +-
 xen/include/xen/lib/x86/msr.h               | 24 +++++++++++++++++++++++-
 xen/lib/x86/msr.c                           |  2 ++
 5 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/tools/tests/cpu-policy/test-cpu-policy.c 
b/tools/tests/cpu-policy/test-cpu-policy.c
index 7ba9707236..0fa209f1ea 100644
--- a/tools/tests/cpu-policy/test-cpu-policy.c
+++ b/tools/tests/cpu-policy/test-cpu-policy.c
@@ -374,6 +374,11 @@ static void test_msr_deserialise_failure(void)
             .msr = { .idx = 0xce, .val = ~0ull },
             .rc = -EOVERFLOW,
         },
+        {
+            .name = "truncated val",
+            .msr = { .idx = 0x10a, .val = ~0ull },
+            .rc = -EOVERFLOW,
+        },
     };
 
     printf("Testing MSR deserialise failure:\n");
diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index ca4307e19f..c3862033eb 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -220,8 +220,10 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t 
*val)
         break;
 
     case MSR_ARCH_CAPABILITIES:
-        /* Not implemented yet. */
-        goto gp_fault;
+        if ( !cp->feat.arch_caps )
+            goto gp_fault;
+        *val = mp->arch_caps.raw;
+        break;
 
     case MSR_INTEL_MISC_FEATURES_ENABLES:
         *val = msrs->misc_features_enables.raw;
diff --git a/xen/include/public/arch-x86/cpufeatureset.h 
b/xen/include/public/arch-x86/cpufeatureset.h
index ce3deaa5c7..fc733e64f6 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -268,7 +268,7 @@ XEN_CPUFEATURE(CET_IBT,       9*32+20) /*   CET - Indirect 
Branch Tracking */
 XEN_CPUFEATURE(IBRSB,         9*32+26) /*A  IBRS and IBPB support (used by 
Intel) */
 XEN_CPUFEATURE(STIBP,         9*32+27) /*A  STIBP */
 XEN_CPUFEATURE(L1D_FLUSH,     9*32+28) /*S  MSR_FLUSH_CMD and L1D flush. */
-XEN_CPUFEATURE(ARCH_CAPS,     9*32+29) /*   IA32_ARCH_CAPABILITIES MSR */
+XEN_CPUFEATURE(ARCH_CAPS,     9*32+29) /*a  IA32_ARCH_CAPABILITIES MSR */
 XEN_CPUFEATURE(CORE_CAPS,     9*32+30) /*   IA32_CORE_CAPABILITIES MSR */
 XEN_CPUFEATURE(SSBD,          9*32+31) /*A  MSR_SPEC_CTRL.SSBD available */
 
diff --git a/xen/include/xen/lib/x86/msr.h b/xen/include/xen/lib/x86/msr.h
index 203c713320..48ba4a59c0 100644
--- a/xen/include/xen/lib/x86/msr.h
+++ b/xen/include/xen/lib/x86/msr.h
@@ -3,7 +3,7 @@
 #define XEN_LIB_X86_MSR_H
 
 /* Maximum number of MSRs written when serialising msr_policy. */
-#define MSR_MAX_SERIALISED_ENTRIES 1
+#define MSR_MAX_SERIALISED_ENTRIES 2
 
 /* MSR policy object for shared per-domain MSRs */
 struct msr_policy
@@ -23,6 +23,28 @@ struct msr_policy
             bool cpuid_faulting:1;
         };
     } platform_info;
+
+    /*
+     * 0x0000010a - MSR_ARCH_CAPABILITIES
+     *
+     * This is an Intel-only MSR, which provides miscellaneous enumeration,
+     * including those which indicate that microarchitectrual sidechannels are
+     * fixed in hardware.
+     */
+    union {
+        uint32_t raw;
+        struct {
+            bool rdcl_no:1;
+            bool ibrs_all:1;
+            bool rsba:1;
+            bool skip_l1dfl:1;
+            bool ssb_no:1;
+            bool mds_no:1;
+            bool if_pschange_mc_no:1;
+            bool tsx_ctrl:1;
+            bool taa_no:1;
+        };
+    } arch_caps;
 };
 
 #ifdef __XEN__
diff --git a/xen/lib/x86/msr.c b/xen/lib/x86/msr.c
index 171abf7008..7d71e92a38 100644
--- a/xen/lib/x86/msr.c
+++ b/xen/lib/x86/msr.c
@@ -39,6 +39,7 @@ int x86_msr_copy_to_buffer(const struct msr_policy *p,
     })
 
     COPY_MSR(MSR_INTEL_PLATFORM_INFO, p->platform_info.raw);
+    COPY_MSR(MSR_ARCH_CAPABILITIES,   p->arch_caps.raw);
 
 #undef COPY_MSR
 
@@ -99,6 +100,7 @@ int x86_msr_copy_from_buffer(struct msr_policy *p,
 })
 
         case MSR_INTEL_PLATFORM_INFO: ASSIGN(platform_info.raw); break;
+        case MSR_ARCH_CAPABILITIES:   ASSIGN(arch_caps.raw);     break;
 
 #undef ASSIGN
 
--
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