[PATCH] target/i386: Add bus lock debug exception support

[PATCH] target/i386: Add bus lock debug exception support

[Chenyi Qiang]

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>
---
 target/i386/cpu.c | 2 +-
 target/i386/cpu.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index ae89024d36..55f3b5829f 100644
--- a/target/i386/cpu.c
+++ b/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, NULL,
         },
         .cpuid = {
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index d23a5b340a..417f49b721 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -762,6 +762,8 @@ 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 */
-- 
2.17.1

Re: [PATCH] target/i386: Add bus lock debug exception support

[Paolo Bonzini]

On 02/02/21 10:02, Chenyi Qiang wrote:
> 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>
> ---
>   target/i386/cpu.c | 2 +-
>   target/i386/cpu.h | 2 ++
>   2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index ae89024d36..55f3b5829f 100644
> --- a/target/i386/cpu.c
> +++ b/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, NULL,
>           },
>           .cpuid = {
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index d23a5b340a..417f49b721 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -762,6 +762,8 @@ 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 */
> 

Queued, thanks.

Paolo