diff mbox series

[v9,12/36] x86/fred: Update MSR_IA32_FRED_RSP0 during task switch

Message ID 20230731063317.3720-13-xin3.li@intel.com (mailing list archive)
State Superseded
Headers show
Series x86: enable FRED for x86-64 | expand

Commit Message

Li, Xin3 July 31, 2023, 6:32 a.m. UTC 
From: "H. Peter Anvin (Intel)" <hpa@zytor.com>

MSR_IA32_FRED_RSP0 is used during ring 3 event delivery, and needs to
be updated to point to the top of next task stack during task switch.

Update MSR_IA32_FRED_RSP0 with WRMSR instruction for now, and will use
WRMSRNS/WRMSRLIST for performance once it gets upstreamed.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Tested-by: Shan Kang <shan.kang@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
 arch/x86/include/asm/switch_to.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index f42dbf17f52b..6c911fd400b2 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -70,9 +70,16 @@  static inline void update_task_stack(struct task_struct *task)
 #ifdef CONFIG_X86_32
 	this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
 #else
-	/* Xen PV enters the kernel on the thread stack. */
-	if (cpu_feature_enabled(X86_FEATURE_XENPV))
+	if (cpu_feature_enabled(X86_FEATURE_FRED)) {
+		/*
+		 * Will use WRMSRNS/WRMSRLIST for performance once it's upstreamed.
+		 */
+		wrmsrl(MSR_IA32_FRED_RSP0,
+		       (unsigned long)task_stack_page(task) + THREAD_SIZE);
+	} else if (cpu_feature_enabled(X86_FEATURE_XENPV)) {
+		/* Xen PV enters the kernel on the thread stack. */
 		load_sp0(task_top_of_stack(task));
+	}
 #endif
 }