linux-kernel - [PATCH V10 07/44] x86/fault: Adjust WARN

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Date:   Tue, 19 Apr 2022 10:06:12 -0700
From:   ira.weiny@...el.com
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V10 07/44] x86/fault: Adjust WARN_ON for pkey fault

From: Ira Weiny <ira.weiny@...el.com>

Previously if a protection key fault occurred on a kernel address it
indicated something wrong because user page mappings are not supposed to
be in the kernel address space.

With the addition of PKS, pkey faults may now happen on kernel mappings.

If PKS is enabled, avoid the warning in the fault path.  Simplify the
comment.

Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes for V9
	From Dave Hansen
		Clarify the comment and commit message
---
 arch/x86/mm/fault.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index d0074c6ed31a..5599109d1124 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1148,11 +1148,11 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
 		   unsigned long address)
 {
 	/*
-	 * Protection keys exceptions only happen on user pages.  We
-	 * have no user pages in the kernel portion of the address
-	 * space, so do not expect them here.
+	 * PF_PF faults should only occur on kernel
+	 * addresses when supervisor pkeys are enabled.
 	 */
-	WARN_ON_ONCE(hw_error_code & X86_PF_PK);
+	WARN_ON_ONCE(!cpu_feature_enabled(X86_FEATURE_PKS) &&
+		     (hw_error_code & X86_PF_PK));
 
 #ifdef CONFIG_X86_32
 	/*
-- 
2.35.1