linux-kernel - [tip: x86/fpu] x86/cpu: Write the default PKRU value when enabling PKE

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Date:   Wed, 23 Jun 2021 22:09:08 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...e.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/fpu] x86/cpu: Write the default PKRU value when enabling PKE

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     fa8c84b77a54bf3cf351c8b4b26a5aca27a14013
Gitweb:        https://git.kernel.org/tip/fa8c84b77a54bf3cf351c8b4b26a5aca27a14013
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Wed, 23 Jun 2021 14:02:10 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Wed, 23 Jun 2021 19:14:54 +02:00

x86/cpu: Write the default PKRU value when enabling PKE

In preparation of making the PKRU management more independent from XSTATES,
write the default PKRU value into the hardware right after enabling PKRU in
CR4. This ensures that switch_to() and copy_thread() have the correct
setting for init task and the per CPU idle threads right away.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20210623121455.622983906@linutronix.de
---
 arch/x86/kernel/cpu/common.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index dbfb335..ca668ef 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -480,6 +480,8 @@ static __always_inline void setup_pku(struct cpuinfo_x86 *c)
 	}
 
 	cr4_set_bits(X86_CR4_PKE);
+	/* Load the default PKRU value */
+	pkru_write_default();
 }
 
 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS