[PATCH 0/5] x86/xen: Get rid of Xen private lazy MMU mode tracking

[PATCH 0/5] x86/xen: Get rid of Xen private lazy MMU mode tracking

[Juergen Gross]

With generic lazy MMU mode tracking being available, there is no real
need for having Xen PV specific code to track lazy MMU mode, too.

This makes it possible to drop two paravirt hooks.

Note that this series is based on my series "x86/xen: Do some Xen-PV
related cleanups" [1].

[1]: https://lore.kernel.org/lkml/20260522152114.77319-1-jgross@suse.com/

Juergen Gross (5):
  x86/xen: Drop lazy mode from trace entries
  x86/xen: Change interface of xen_mc_issue()
  mm: Refactor lazy_mmu_mode_pause() and lazy_mmu_mode_resume()
  x86/xen: Get rid of last XEN_LAZY_MMU uses
  x86/xen: Replace generic lazy tracking with cpu specific one

 arch/x86/include/asm/paravirt.h       |  9 ++--
 arch/x86/include/asm/paravirt_types.h | 11 +----
 arch/x86/include/asm/xen/hypervisor.h | 25 +---------
 arch/x86/kernel/paravirt.c            |  6 +--
 arch/x86/xen/enlighten_pv.c           | 30 +++++-------
 arch/x86/xen/mmu_pv.c                 | 66 +++++++++------------------
 arch/x86/xen/xen-ops.h                | 12 +++--
 include/linux/pgtable.h               | 56 ++++++++++++++++++-----
 include/trace/events/xen.h            | 33 ++++++++------
 9 files changed, 112 insertions(+), 136 deletions(-)

-- 
2.54.0

[PATCH 1/5] x86/xen: Drop lazy mode from trace entries

[Juergen Gross]

Drop the lazy mode (cpu or mmu) from the xen_mc_batch and xen_mc_issue
trace entries.

This is done in preparation of removing the xen_lazy_mode percpu
variable.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/xen/xen-ops.h     | 11 +++++++----
 include/trace/events/xen.h | 33 +++++++++++++++++++--------------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 6808010ac379..dc892f421f25 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -98,7 +98,7 @@ static inline void xen_mc_batch(void)
 
 	/* need to disable interrupts until this entry is complete */
 	local_irq_save(flags);
-	trace_xen_mc_batch(xen_get_lazy_mode());
+	trace_xen_mc_batch(flags);
 	__this_cpu_write(xen_mc_irq_flags, flags);
 }
 
@@ -114,13 +114,16 @@ void xen_mc_flush(void);
 /* Issue a multicall if we're not in a lazy mode */
 static inline void xen_mc_issue(unsigned mode)
 {
-	trace_xen_mc_issue(mode);
+	bool flush = !(xen_get_lazy_mode() & mode);
+	unsigned long flags = this_cpu_read(xen_mc_irq_flags);
 
-	if ((xen_get_lazy_mode() & mode) == 0)
+	trace_xen_mc_issue(flush, flags);
+
+	if (flush)
 		xen_mc_flush();
 
 	/* restore flags saved in xen_mc_batch */
-	local_irq_restore(this_cpu_read(xen_mc_irq_flags));
+	local_irq_restore(flags);
 }
 
 /* Set up a callback to be called when the current batch is flushed */
diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h
index e3f139f0bc78..ad384969e2cb 100644
--- a/include/trace/events/xen.h
+++ b/include/trace/events/xen.h
@@ -12,24 +12,29 @@
 struct multicall_entry;
 
 /* Multicalls */
-DECLARE_EVENT_CLASS(xen_mc__batch,
-	    TP_PROTO(enum xen_lazy_mode mode),
-	    TP_ARGS(mode),
+TRACE_EVENT(xen_mc_batch,
+	    TP_PROTO(unsigned long flags),
+	    TP_ARGS(flags),
 	    TP_STRUCT__entry(
-		    __field(enum xen_lazy_mode, mode)
+		    __field(unsigned long, flags)
 		    ),
-	    TP_fast_assign(__entry->mode = mode),
-	    TP_printk("start batch LAZY_%s",
-		      (__entry->mode == XEN_LAZY_MMU) ? "MMU" :
-		      (__entry->mode == XEN_LAZY_CPU) ? "CPU" : "NONE")
+	    TP_fast_assign(__entry->flags = flags),
+	    TP_printk("start batch lazy flags %lx", __entry->flags)
 	);
-#define DEFINE_XEN_MC_BATCH(name)			\
-	DEFINE_EVENT(xen_mc__batch, name,		\
-		TP_PROTO(enum xen_lazy_mode mode),	\
-		     TP_ARGS(mode))
 
-DEFINE_XEN_MC_BATCH(xen_mc_batch);
-DEFINE_XEN_MC_BATCH(xen_mc_issue);
+TRACE_EVENT(xen_mc_issue,
+	    TP_PROTO(bool flush, unsigned long flags),
+	    TP_ARGS(flush, flags),
+	    TP_STRUCT__entry(
+		    __field(unsigned long, flags)
+		    __field(bool, flush)
+		    ),
+	    TP_fast_assign(__entry->flush = flush;
+			   __entry->flags = flags;
+		    ),
+	    TP_printk("flush: %s, flags %lx",
+		      __entry->flush ? "yes" : "no", __entry->flags)
+	);
 
 TRACE_DEFINE_SIZEOF(ulong);
 
-- 
2.54.0

Re: [PATCH 0/5] x86/xen: Get rid of Xen private lazy MMU mode tracking

[David Hildenbrand (Arm)]

On 5/26/26 17:05, Juergen Gross wrote:
> With generic lazy MMU mode tracking being available, there is no real
> need for having Xen PV specific code to track lazy MMU mode, too.
> 
> This makes it possible to drop two paravirt hooks.

Nice!

-- 
Cheers,

David