linux-kernel - [PATCH v4 09/11] x86/cpufeatures: Re-enable ENQCMD

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Date:   Mon,  7 Feb 2022 15:02:52 -0800
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     "Thomas Gleixner" <tglx@...utronix.de>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>,
        "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Andy Lutomirski" <luto@...nel.org>,
        "Tony Luck" <tony.luck@...el.com>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        "Joerg Roedel" <joro@...tes.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Jacob Pan" <jacob.jun.pan@...ux.intel.com>,
        "Ashok Raj" <ashok.raj@...el.com>,
        "Ravi V Shankar" <ravi.v.shankar@...el.com>
Cc:     iommu@...ts.linux-foundation.org, "x86" <x86@...nel.org>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATCH v4 09/11] x86/cpufeatures: Re-enable ENQCMD

Since ENQCMD is handled by #GP fix up, it can be re-enabled.

The ENQCMD feature can only be used if CONFIG_INTEL_IOMMU_SVM is set. Add
X86_FEATURE_ENQCMD to the disabled features mask as appropriate so that
cpu_feature_enabled() can be used to check the feature.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
---
v4:
- Add "Reviewed-by: Thomas Gleixner <tglx@...utronix.de>" (Thomas).

v2:
- Update the commit message (Tony).

 arch/x86/include/asm/disabled-features.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 8f28fafa98b3..1231d63f836d 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -56,8 +56,11 @@
 # define DISABLE_PTI		(1 << (X86_FEATURE_PTI & 31))
 #endif
 
-/* Force disable because it's broken beyond repair */
-#define DISABLE_ENQCMD		(1 << (X86_FEATURE_ENQCMD & 31))
+#ifdef CONFIG_INTEL_IOMMU_SVM
+# define DISABLE_ENQCMD		0
+#else
+# define DISABLE_ENQCMD		(1 << (X86_FEATURE_ENQCMD & 31))
+#endif
 
 #ifdef CONFIG_X86_SGX
 # define DISABLE_SGX	0
-- 
2.35.1