linux-kernel - [PATCH v8 16/33] x86/fred: add a page fault entry stub for FRED

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Message-Id: <20230410081438.1750-17-xin3.li@intel.com>
Date:   Mon, 10 Apr 2023 01:14:21 -0700
From:   Xin Li <xin3.li@...el.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, peterz@...radead.org,
        andrew.cooper3@...rix.com, seanjc@...gle.com, pbonzini@...hat.com,
        ravi.v.shankar@...el.com, jiangshanlai@...il.com,
        shan.kang@...el.com
Subject: [PATCH v8 16/33] x86/fred: add a page fault entry stub for FRED

From: "H. Peter Anvin (Intel)" <hpa@...or.com>

Add a page fault entry stub for FRED.

On a FRED system, the faulting address (CR2) is passed on the stack,
to avoid the problem of transient state. Thus we get the page fault
address from the stack instead of CR2.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
Tested-by: Shan Kang <shan.kang@...el.com>
Signed-off-by: Xin Li <xin3.li@...el.com>
---
 arch/x86/include/asm/fred.h |  2 ++
 arch/x86/mm/fault.c         | 20 ++++++++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h
index b59397411ab9..4ff05d350066 100644
--- a/arch/x86/include/asm/fred.h
+++ b/arch/x86/include/asm/fred.h
@@ -99,6 +99,8 @@ static __always_inline unsigned long fred_event_data(struct pt_regs *regs)
 #define DEFINE_FRED_HANDLER(f) noinstr DECLARE_FRED_HANDLER(f)
 typedef DECLARE_FRED_HANDLER((*fred_handler));
 
+DECLARE_FRED_HANDLER(fred_exc_page_fault);
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* CONFIG_X86_FRED */
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index a498ae1fbe66..0f946121de14 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -33,6 +33,7 @@
 #include <asm/kvm_para.h>		/* kvm_handle_async_pf		*/
 #include <asm/vdso.h>			/* fixup_vdso_exception()	*/
 #include <asm/irq_stack.h>
+#include <asm/fred.h>			/* fred_event_data()	*/
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -1507,9 +1508,10 @@ handle_page_fault(struct pt_regs *regs, unsigned long error_code,
 	}
 }
 
-DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
+static __always_inline void page_fault_common(struct pt_regs *regs,
+					      unsigned int error_code,
+					      unsigned long address)
 {
-	unsigned long address = read_cr2();
 	irqentry_state_t state;
 
 	prefetchw(&current->mm->mmap_lock);
@@ -1556,3 +1558,17 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 
 	irqentry_exit(regs, state);
 }
+
+DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
+{
+	page_fault_common(regs, error_code, read_cr2());
+}
+
+#ifdef CONFIG_X86_FRED
+
+DEFINE_FRED_HANDLER(fred_exc_page_fault)
+{
+	page_fault_common(regs, regs->orig_ax, fred_event_data(regs));
+}
+
+#endif /* CONFIG_X86_FRED */
-- 
2.34.1