target/i386: Add bus lock debug exception support

Bus lock debug exception is a feature that can notify the kernel by
generate an #DB trap after the instruction acquires a bus lock when
CPL>0. This allows the kernel to enforce user application throttling or
mitigations.

This feature is enumerated via CPUID.(EAX=7,ECX=0).ECX[bit 24].

Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20210202090224.13274-1-chenyi.qiang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: Qiangcy

target/i386/cpu.c

@@ -963,7 +963,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
             "avx512bitalg", NULL, "avx512-vpopcntdq", NULL,
             "la57", NULL, NULL, NULL,
             NULL, NULL, "rdpid", NULL,
-            NULL, "cldemote", NULL, "movdiri",
+            "bus-lock-detect", "cldemote", NULL, "movdiri",
             "movdir64b", NULL, NULL, "pks",
         },
         .cpuid = {

target/i386/cpu.h

@@ -769,6 +769,8 @@ typedef uint64_t FeatureWordArray[FEATURE_WORDS];
 #define CPUID_7_0_ECX_LA57              (1U << 16)
 /* Read Processor ID */
 #define CPUID_7_0_ECX_RDPID             (1U << 22)
+/* Bus Lock Debug Exception */
+#define CPUID_7_0_ECX_BUS_LOCK_DETECT   (1U << 24)
 /* Cache Line Demote Instruction */
 #define CPUID_7_0_ECX_CLDEMOTE          (1U << 25)
 /* Move Doubleword as Direct Store Instruction */