[Xen-devel] [PATCH v10 16/16] microcode/intel: writeback and invalidate cache conditionally

[Chao Gao <chao.gao@xxxxxxxxx>]

It is needed to mitigate some issues on this specific Broadwell CPU.

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
 xen/arch/x86/microcode_intel.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/xen/arch/x86/microcode_intel.c b/xen/arch/x86/microcode_intel.c
index bcef668..4e5e7f9 100644
--- a/xen/arch/x86/microcode_intel.c
+++ b/xen/arch/x86/microcode_intel.c
@@ -305,6 +305,31 @@ static bool is_blacklisted(void)
     return false;
 }
 
+static void microcode_quirk(void)
+{
+    struct cpuinfo_x86 *c;
+    uint64_t llc_size;
+
+    /*
+     * Don't refer to current_cpu_data, which isn't fully initialized
+     * before this stage.
+     */
+    if ( system_state < SYS_STATE_smp_boot )
+        return;
+
+    c = &current_cpu_data;
+    llc_size = c->x86_cache_size * 1024ULL;
+    do_div(llc_size, c->x86_max_cores);
+
+    /*
+     * To mitigate some issues on this specific Broadwell CPU, writeback and
+     * invalidate cache regardless of ucode revision.
+     */
+    if ( c->x86 == 6 && c->x86_model == 0x4F && c->x86_mask == 0x1 &&
+         llc_size > 2621440 )
+        wbinvd();
+}
+
 static int apply_microcode(const struct microcode_patch *patch)
 {
     uint64_t msr_content;
@@ -323,6 +348,8 @@ static int apply_microcode(const struct microcode_patch 
*patch)
 
     BUG_ON(local_irq_is_enabled());
 
+    microcode_quirk();
+
     /* write microcode via MSR 0x79 */
     wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc_intel->bits);
     wrmsrl(MSR_IA32_UCODE_REV, 0x0ULL);
-- 
1.8.3.1


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