Subject: Re: linux-next: manual merge of the xen-tip tree with the tip tree

From: Thomas Gleixner <[email-masked]>
Date: Thu, 31 Aug 2017 11:00:31 +0200 (CEST)

On Thu, 31 Aug 2017, Thomas Gleixner wrote:
> Hrm. For some reason I missed to remove these defines after getting rid of
> the tracing idt.
> 
> I'll remove that now in tip and pull in the XEN stuff to see what needs to
> be done.

I pushed out the removal of the trace leftovers. Talked to Juergen on IRC
and he suggested to revert the XEN patch in the xen tree and merge it
through tip.

I've applied it on top of tip:x86/apic and fixed up the merge conflicts
mindlessly. Patch below.

Juergen, can you please check the result?

Thanks,

	tglx

8<-------------
Subject: xen: Get rid of paravirt op adjust_exception_frame
From: Juergen Gross <[email-masked]>
Date: Fri, 11 Aug 2017 16:54:48 +0200

When running as Xen pv-guest the exception frame on the stack contains
%r11 and %rcx additional to the other data pushed by the processor.

Instead of having a paravirt op being called for each exception type
prepend the Xen specific code to each exception entry. When running as
Xen pv-guest just use the exception entry with prepended instructions,
otherwise use the entry without the Xen specific code.

Signed-off-by: Juergen Gross <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Link: http://lkml.kernel.org/r/[email-masked]

---
 arch/x86/entry/entry_64.S             |   11 +--
 arch/x86/entry/entry_64_compat.S      |    1 
 arch/x86/include/asm/paravirt.h       |    5 -
 arch/x86/include/asm/paravirt_types.h |    4 -
 arch/x86/include/asm/proto.h          |    3 +
 arch/x86/include/asm/traps.h          |    3 -
 arch/x86/kernel/asm-offsets_64.c      |    1 
 arch/x86/kernel/paravirt.c            |    3 -
 arch/x86/xen/enlighten_pv.c           |   96 ++++++++++++++++++++++------------
 arch/x86/xen/irq.c                    |    3 -
 arch/x86/xen/xen-ops.h                |    1 
 11 files changed, 70 insertions(+), 61 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -816,7 +816,6 @@ ENTRY(\sym)
 	.endif
 
 	ASM_CLAC
-	PARAVIRT_ADJUST_EXCEPTION_FRAME
 
 	.ifeq \has_error_code
 	pushq	$-1				/* ORIG_RAX: no syscall to restart */
@@ -962,7 +961,7 @@ ENTRY(do_softirq_own_stack)
 ENDPROC(do_softirq_own_stack)
 
 #ifdef CONFIG_XEN
-idtentry xen_hypervisor_callback xen_do_hypervisor_callback has_error_code=0
+idtentry hypervisor_callback xen_do_hypervisor_callback has_error_code=0
 
 /*
  * A note on the "critical region" in our callback handler.
@@ -1029,8 +1028,6 @@ ENTRY(xen_failsafe_callback)
 	movq	8(%rsp), %r11
 	addq	$0x30, %rsp
 	pushq	$0				/* RIP */
-	pushq	%r11
-	pushq	%rcx
 	UNWIND_HINT_IRET_REGS offset=8
 	jmp	general_protection
 1:	/* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */
@@ -1061,9 +1058,8 @@ idtentry int3			do_int3			has_error_code
 idtentry stack_segment		do_stack_segment	has_error_code=1
 
 #ifdef CONFIG_XEN
-idtentry xen_debug		do_debug		has_error_code=0
-idtentry xen_int3		do_int3			has_error_code=0
-idtentry xen_stack_segment	do_stack_segment	has_error_code=1
+idtentry xendebug		do_debug		has_error_code=0
+idtentry xenint3		do_int3			has_error_code=0
 #endif
 
 idtentry general_protection	do_general_protection	has_error_code=1
@@ -1227,6 +1223,7 @@ ENTRY(error_exit)
 END(error_exit)
 
 /* Runs on exception stack */
+/* XXX: broken on Xen PV */
 ENTRY(nmi)
 	UNWIND_HINT_IRET_REGS
 	/*
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -293,7 +293,6 @@ ENTRY(entry_INT80_compat)
 	/*
 	 * Interrupts are off on entry.
 	 */
-	PARAVIRT_ADJUST_EXCEPTION_FRAME
 	ASM_CLAC			/* Do this early to minimize exposure */
 	SWAPGS
 
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -960,11 +960,6 @@ extern void default_banner(void);
 #define GET_CR2_INTO_RAX				\
 	call PARA_INDIRECT(pv_mmu_ops+PV_MMU_read_cr2)
 
-#define PARAVIRT_ADJUST_EXCEPTION_FRAME					\
-	PARA_SITE(PARA_PATCH(pv_irq_ops, PV_IRQ_adjust_exception_frame), \
-		  CLBR_NONE,						\
-		  call PARA_INDIRECT(pv_irq_ops+PV_IRQ_adjust_exception_frame))
-
 #define USERGS_SYSRET64							\
 	PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret64),	\
 		  CLBR_NONE,						\
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -195,10 +195,6 @@ struct pv_irq_ops {
 
 	void (*safe_halt)(void);
 	void (*halt)(void);
-
-#ifdef CONFIG_X86_64
-	void (*adjust_exception_frame)(void);
-#endif
 } __no_randomize_layout;
 
 struct pv_mmu_ops {
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -24,6 +24,9 @@ void entry_SYSENTER_compat(void);
 void __end_entry_SYSENTER_compat(void);
 void entry_SYSCALL_compat(void);
 void entry_INT80_compat(void);
+#if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)
+void xen_entry_INT80_compat(void);
+#endif
 #endif
 
 void x86_configure_nx(void);
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -13,9 +13,6 @@ asmlinkage void divide_error(void);
 asmlinkage void debug(void);
 asmlinkage void nmi(void);
 asmlinkage void int3(void);
-asmlinkage void xen_debug(void);
-asmlinkage void xen_int3(void);
-asmlinkage void xen_stack_segment(void);
 asmlinkage void overflow(void);
 asmlinkage void bounds(void);
 asmlinkage void invalid_op(void);
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -20,7 +20,6 @@ static char syscalls_ia32[] = {
 int main(void)
 {
 #ifdef CONFIG_PARAVIRT
-	OFFSET(PV_IRQ_adjust_exception_frame, pv_irq_ops, adjust_exception_frame);
 	OFFSET(PV_CPU_usergs_sysret64, pv_cpu_ops, usergs_sysret64);
 	OFFSET(PV_CPU_swapgs, pv_cpu_ops, swapgs);
 	BLANK();
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -319,9 +319,6 @@ struct pv_time_ops pv_time_ops = {
 	.irq_enable = __PV_IS_CALLEE_SAVE(native_irq_enable),
 	.safe_halt = native_safe_halt,
 	.halt = native_halt,
-#ifdef CONFIG_X86_64
-	.adjust_exception_frame = paravirt_nop,
-#endif
 };
 
 __visible struct pv_cpu_ops pv_cpu_ops = {
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -586,6 +586,68 @@ static void xen_write_ldt_entry(struct d
 	preempt_enable();
 }
 
+#ifdef CONFIG_X86_64
+static struct {
+	void (*orig)(void);
+	void (*xen)(void);
+	bool ist_okay;
+} trap_array[] = {
+	{ debug, xen_xendebug, true },
+	{ int3, xen_xenint3, true },
+	{ double_fault, xen_double_fault, true },
+#ifdef CONFIG_X86_MCE
+	{ machine_check, xen_machine_check, true },
+#endif
+	{ nmi, xen_nmi, true },
+	{ overflow, xen_overflow, false },
+#ifdef CONFIG_IA32_EMULATION
+	{ entry_INT80_compat, xen_entry_INT80_compat, false },
+#endif
+	{ page_fault, xen_page_fault, false },
+	{ divide_error, xen_divide_error, false },
+	{ bounds, xen_bounds, false },
+	{ invalid_op, xen_invalid_op, false },
+	{ device_not_available, xen_device_not_available, false },
+	{ coprocessor_segment_overrun, xen_coprocessor_segment_overrun, false },
+	{ invalid_TSS, xen_invalid_TSS, false },
+	{ segment_not_present, xen_segment_not_present, false },
+	{ stack_segment, xen_stack_segment, false },
+	{ general_protection, xen_general_protection, false },
+	{ spurious_interrupt_bug, xen_spurious_interrupt_bug, false },
+	{ coprocessor_error, xen_coprocessor_error, false },
+	{ alignment_check, xen_alignment_check, false },
+	{ simd_coprocessor_error, xen_simd_coprocessor_error, false },
+#ifdef CONFIG_TRACING
+	{ trace_page_fault, xen_trace_page_fault, false },
+#endif
+};
+
+static bool get_trap_addr(unsigned long *addr, unsigned int ist)
+{
+	unsigned int nr;
+	bool ist_okay = false;
+
+	/*
+	 * Replace trap handler addresses by Xen specific ones.
+	 * Check for known traps using IST and whitelist them.
+	 * The debugger ones are the only ones we care about.
+	 * Xen will handle faults like double_fault, * so we should never see
+	 * them.  Warn if there's an unexpected IST-using fault handler.
+	 */
+	for (nr = 0; nr < ARRAY_SIZE(trap_array); nr++)
+		if (*addr == (unsigned long)trap_array[nr].orig) {
+			*addr = (unsigned long)trap_array[nr].xen;
+			ist_okay = trap_array[nr].ist_okay;
+			break;
+		}
+
+	if (WARN_ON(ist != 0 && !ist_okay))
+		return false;
+
+	return true;
+}
+#endif
+
 static int cvt_gate_to_trap(int vector, const gate_desc *val,
 			    struct trap_info *info)
 {
@@ -598,40 +660,8 @@ static int cvt_gate_to_trap(int vector,
 
 	addr = gate_offset(val);
 #ifdef CONFIG_X86_64
-	/*
-	 * Look for known traps using IST, and substitute them
-	 * appropriately.  The debugger ones are the only ones we care
-	 * about.  Xen will handle faults like double_fault,
-	 * so we should never see them.  Warn if
-	 * there's an unexpected IST-using fault handler.
-	 */
-	if (addr == (unsigned long)debug)
-		addr = (unsigned long)xen_debug;
-	else if (addr == (unsigned long)int3)
-		addr = (unsigned long)xen_int3;
-	else if (addr == (unsigned long)stack_segment)
-		addr = (unsigned long)xen_stack_segment;
-	else if (addr == (unsigned long)double_fault) {
-		/* Don't need to handle these */
+	if (!get_trap_addr(&addr, val->bits.ist))
 		return 0;
-#ifdef CONFIG_X86_MCE
-	} else if (addr == (unsigned long)machine_check) {
-		/*
-		 * when xen hypervisor inject vMCE to guest,
-		 * use native mce handler to handle it
-		 */
-		;
-#endif
-	} else if (addr == (unsigned long)nmi)
-		/*
-		 * Use the native version as well.
-		 */
-		;
-	else {
-		/* Some other trap using IST? */
-		if (WARN_ON(val->bits.ist != 0))
-			return 0;
-	}
 #endif	/* CONFIG_X86_64 */
 	info->address = addr;
 
--- a/arch/x86/xen/irq.c
+++ b/arch/x86/xen/irq.c
@@ -123,9 +123,6 @@ static const struct pv_irq_ops xen_irq_o
 
 	.safe_halt = xen_safe_halt,
 	.halt = xen_halt,
-#ifdef CONFIG_X86_64
-	.adjust_exception_frame = xen_adjust_exception_frame,
-#endif
 };
 
 void __init xen_init_irq_ops(void)
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -138,7 +138,6 @@ static inline void __init xen_efi_init(v
 __visible void xen_iret(void);
 __visible void xen_sysret32(void);
 __visible void xen_sysret64(void);
-__visible void xen_adjust_exception_frame(void);
 
 extern int xen_panic_handler_init(void);