linux-kernel - [PATCH v2 3/5] x86: drop 32-bit Xen PV guest code in update_task

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Date:   Fri,  4 Nov 2022 08:26:59 +0100
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v2 3/5] x86: drop 32-bit Xen PV guest code in update_task_stack()

Testing for Xen PV guest mode in a 32-bit only code section can be
dropped, as Xen PV guests are supported in 64-bit mode only.

While at it switch from boot_cpu_has() to cpu_feature_enabled() in the
64-bit part of the code.

Signed-off-by: Juergen Gross <jgross@...e.com>
---
 arch/x86/include/asm/switch_to.h | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index c08eb0fdd11f..5c91305d09d2 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -66,13 +66,10 @@ static inline void update_task_stack(struct task_struct *task)
 {
 	/* sp0 always points to the entry trampoline stack, which is constant: */
 #ifdef CONFIG_X86_32
-	if (static_cpu_has(X86_FEATURE_XENPV))
-		load_sp0(task->thread.sp0);
-	else
-		this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
+	this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0);
 #else
 	/* Xen PV enters the kernel on the thread stack. */
-	if (static_cpu_has(X86_FEATURE_XENPV))
+	if (cpu_feature_enabled(X86_FEATURE_XENPV))
 		load_sp0(task_top_of_stack(task));
 #endif
 }
-- 
2.35.3