linux-kernel - [RFC PATCH v3 17/32] x86/fred: add a page fault entry stub for FRED

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Date:   Thu, 23 Feb 2023 23:01:30 -0800
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
Subject: [RFC PATCH v3 17/32] 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>
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 f4de2cdd1c7f..de300bda60ee 100644
--- a/arch/x86/include/asm/fred.h
+++ b/arch/x86/include/asm/fred.h
@@ -94,6 +94,8 @@ 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 7b0d4ab894c8..f31053f32048 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>
@@ -1528,9 +1529,10 @@ 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);
@@ -1577,3 +1579,17 @@ 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