Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Alexander Shishkin <alexander.shishkin@linux.intel.com>
To:     linux-kernel@vger.kernel.org, x86@kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ravi Shankar <ravi.v.shankar@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Sohil Mehta <sohil.mehta@intel.com>
Cc:     Alexander Shishkin <alexander.shishkin@linux.intel.com>
Subject: [PATCH v3 04/12] x86/cpu: Enable LASS during CPU initialization
Date:   Fri,  9 Jun 2023 21:36:24 +0300
Message-Id: <20230609183632.48706-5-alexander.shishkin@linux.intel.com>
In-Reply-To: <20230609183632.48706-1-alexander.shishkin@linux.intel.com>
References: <20230609183632.48706-1-alexander.shishkin@linux.intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Sohil Mehta <sohil.mehta@intel.com>

Being a security feature, enable LASS by default if the platform
supports it.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 arch/x86/kernel/cpu/common.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 80710a68ef7d..315cc67ba93a 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -413,6 +413,12 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c)
 	cr4_clear_bits(X86_CR4_UMIP);
 }
 
+static __always_inline void setup_lass(struct cpuinfo_x86 *c)
+{
+	if (cpu_feature_enabled(X86_FEATURE_LASS))
+		cr4_set_bits(X86_CR4_LASS);
+}
+
 /* These bits should not change their value after CPU init is finished. */
 static const unsigned long cr4_pinned_mask =
 	X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
@@ -1859,6 +1865,7 @@ static void identify_cpu(struct cpuinfo_x86 *c)
 	setup_smep(c);
 	setup_smap(c);
 	setup_umip(c);
+	setup_lass(c);
 
 	/* Enable FSGSBASE instructions if available. */
 	if (cpu_has(c, X86_FEATURE_FSGSBASE)) {
-- 
2.39.2