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Date:   Fri, 20 Nov 2020 12:46:19 +0100
From:   Juergen Gross <jgross@...e.com>
To:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, luto@...nel.org,
        Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>
Subject: [PATCH v2 01/12] x86/xen: use specific Xen pv interrupt entry for MCE

Xen PV guests don't use IST. For machine check interrupts switch to
the same model as debug interrupts.

Signed-off-by: Juergen Gross <jgross@...e.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/idtentry.h |  3 +++
 arch/x86/xen/enlighten_pv.c     | 16 +++++++++++++++-
 arch/x86/xen/xen-asm.S          |  2 +-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index b2442eb0ac2f..3505c0396fa5 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -588,6 +588,9 @@ DECLARE_IDTENTRY_MCE(X86_TRAP_MC,	exc_machine_check);
 #else
 DECLARE_IDTENTRY_RAW(X86_TRAP_MC,	exc_machine_check);
 #endif
+#ifdef CONFIG_XEN_PV
+DECLARE_IDTENTRY_RAW(X86_TRAP_MC,	xenpv_exc_machine_check);
+#endif
 #endif
 
 /* NMI */
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 4409306364dc..9f5e44c1f70a 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -583,6 +583,20 @@ DEFINE_IDTENTRY_RAW(xenpv_exc_debug)
 		exc_debug(regs);
 }
 
+#ifdef CONFIG_X86_MCE
+DEFINE_IDTENTRY_RAW(xenpv_exc_machine_check)
+{
+	/*
+	 * There's no IST on Xen PV, but we still need to dispatch
+	 * to the correct handler.
+	 */
+	if (user_mode(regs))
+		noist_exc_machine_check(regs);
+	else
+		exc_machine_check(regs);
+}
+#endif
+
 struct trap_array_entry {
 	void (*orig)(void);
 	void (*xen)(void);
@@ -603,7 +617,7 @@ static struct trap_array_entry trap_array[] = {
 	TRAP_ENTRY_REDIR(exc_debug,			true  ),
 	TRAP_ENTRY(exc_double_fault,			true  ),
 #ifdef CONFIG_X86_MCE
-	TRAP_ENTRY(exc_machine_check,			true  ),
+	TRAP_ENTRY_REDIR(exc_machine_check,		true  ),
 #endif
 	TRAP_ENTRY_REDIR(exc_nmi,			true  ),
 	TRAP_ENTRY(exc_int3,				false ),
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index 1cb0e84b9161..bc2586730a5b 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -172,7 +172,7 @@ xen_pv_trap asm_exc_spurious_interrupt_bug
 xen_pv_trap asm_exc_coprocessor_error
 xen_pv_trap asm_exc_alignment_check
 #ifdef CONFIG_X86_MCE
-xen_pv_trap asm_exc_machine_check
+xen_pv_trap asm_xenpv_exc_machine_check
 #endif /* CONFIG_X86_MCE */
 xen_pv_trap asm_exc_simd_coprocessor_error
 #ifdef CONFIG_IA32_EMULATION
-- 
2.26.2

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