target/i386: add support for FLUSH_L1D feature

As reported by Intel's doc:
"L1D_FLUSH: Writeback and invalidate the L1 data cache"

If this cpu feature is present in host, allow QEMU to choose whether to
show it to the guest too.
One disadvantage of not exposing it is that the guest will report
a non existing vulnerability in
/sys/devices/system/cpu/vulnerabilities/mmio_stale_data
because the mitigation is present only when the cpu has
	(FLUSH_L1D and MD_CLEAR) or FB_CLEAR
features enabled.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20230201135759.555607-2-eesposit@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 4187759f106fbc5f508689efea731b417df1060e..e5c813199a0d93cac2598d14b36395f6514c0049 100644 (file)
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -863,7 +863,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
             "tsx-ldtrk", NULL, NULL /* pconfig */, "arch-lbr",
             NULL, NULL, "amx-bf16", "avx512-fp16",
             "amx-tile", "amx-int8", "spec-ctrl", "stibp",
-            NULL, "arch-capabilities", "core-capability", "ssbd",
+            "flush-l1d", "arch-capabilities", "core-capability", "ssbd",
         },
         .cpuid = {
             .eax = 7,

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 8ade71ab555d6626d66619c693a8105643cc3229..3c6f9226e1f18a48e06dfa6e314d08429d76afd0 100644 (file)
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -899,6 +899,8 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
 #define CPUID_7_0_EDX_SPEC_CTRL         (1U << 26)
 /* Single Thread Indirect Branch Predictors */
 #define CPUID_7_0_EDX_STIBP             (1U << 27)
+/* Flush L1D cache */
+#define CPUID_7_0_EDX_FLUSH_L1D         (1U << 28)
 /* Arch Capabilities */
 #define CPUID_7_0_EDX_ARCH_CAPABILITIES (1U << 29)
 /* Core Capability */