linux-kernel - [RFC][PATCH 2/6] x86/power: Inline write

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Message-ID: <20230112143825.644480983@infradead.org>
Date:   Thu, 12 Jan 2023 15:31:43 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, Joan Bruguera <joanbrugueram@...il.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        Juergen Gross <jgross@...e.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        xen-devel <xen-devel@...ts.xenproject.org>,
        Jan Beulich <jbeulich@...e.com>,
        Roger Pau Monne <roger.pau@...rix.com>,
        Kees Cook <keescook@...omium.org>, mark.rutland@....com
Subject: [RFC][PATCH 2/6] x86/power: Inline write_cr[04]()

Since we can't do CALL/RET until GS is restored and CR[04] pinning is
of dubious value in this code path, simply write the stored values.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/power/cpu.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -208,11 +208,11 @@ static void notrace __restore_processor_
 #else
 /* CONFIG X86_64 */
 	native_wrmsrl(MSR_EFER, ctxt->efer);
-	native_write_cr4(ctxt->cr4);
+	asm volatile("mov %0,%%cr4": "+r" (ctxt->cr4) : : "memory");
 #endif
 	native_write_cr3(ctxt->cr3);
 	native_write_cr2(ctxt->cr2);
-	native_write_cr0(ctxt->cr0);
+	asm volatile("mov %0,%%cr0": "+r" (ctxt->cr0) : : "memory");
 
 	/* Restore the IDT. */
 	native_load_idt(&ctxt->idt);