* [PATCH 4/5] x86/xen: Get rid of last XEN_LAZY_MMU uses
2026-05-26 15:05 [PATCH 0/5] x86/xen: Get rid of Xen private lazy MMU mode tracking Juergen Gross
@ 2026-05-26 15:05 ` Juergen Gross
2026-06-01 15:08 ` [PATCH 0/5] x86/xen: Get rid of Xen private lazy MMU mode tracking David Hildenbrand (Arm)
1 sibling, 0 replies; 3+ messages in thread
From: Juergen Gross @ 2026-05-26 15:05 UTC (permalink / raw)
To: linux-kernel, x86, virtualization
Cc: Juergen Gross, Ajay Kaher, Alexey Makhalov,
Broadcom internal kernel review list, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, Dave Hansen, H. Peter Anvin,
Boris Ostrovsky, xen-devel
There are only very few use cases of XEN_LAZY_MMU left. Get rid of
them in order to avoid having to call enter_lazy(XEN_LAZY_MMU) and
leave_lazy(XEN_LAZY_MMU).
The query in xen_batched_set_pte() can be replaced by using
is_lazy_mmu_mode_active() instead.
As xen_flush_lazy_mmu() will be called only with lazy MMU mode being
active, the test for the lazy mode can just be dropped.
In xen_start_context_switch() and xen_end_context_switch() use
__task_lazy_mmu_mode_pause() and __task_lazy_mmu_mode_resume(),
allowing to drop xen_enter_lazy_mmu() and xen_leave_lazy_mmu()
completely.
Call arch_flush_lazy_mmu_mode() from arch_leave_lazy_mmu_mode(), as
this is the only required action now.
Drop the lazy mmu enter and leave paravirt hooks, leaving the flush
hook as the only needed one.
Signed-off-by: Juergen Gross <jgross@suse.com>
---
arch/x86/include/asm/paravirt.h | 9 ++++-----
arch/x86/include/asm/paravirt_types.h | 11 +----------
arch/x86/kernel/paravirt.c | 6 +-----
arch/x86/xen/enlighten_pv.c | 7 ++-----
arch/x86/xen/mmu_pv.c | 28 +++------------------------
5 files changed, 11 insertions(+), 50 deletions(-)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index cdfe4007443e..0591aa38fd85 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -483,17 +483,16 @@ static inline void arch_end_context_switch(struct task_struct *next)
static inline void arch_enter_lazy_mmu_mode(void)
{
- PVOP_VCALL0(pv_ops, mmu.lazy_mode.enter);
}
-static inline void arch_leave_lazy_mmu_mode(void)
+static inline void arch_flush_lazy_mmu_mode(void)
{
- PVOP_VCALL0(pv_ops, mmu.lazy_mode.leave);
+ PVOP_VCALL0(pv_ops, mmu.lazy_mode_flush);
}
-static inline void arch_flush_lazy_mmu_mode(void)
+static inline void arch_leave_lazy_mmu_mode(void)
{
- PVOP_VCALL0(pv_ops, mmu.lazy_mode.flush);
+ arch_flush_lazy_mmu_mode();
}
static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx,
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 4f5ae0068aab..b4c4a23e77a1 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -19,15 +19,6 @@ struct cpumask;
struct flush_tlb_info;
struct vm_area_struct;
-#ifdef CONFIG_PARAVIRT_XXL
-struct pv_lazy_ops {
- /* Set deferred update mode, used for batching operations. */
- void (*enter)(void);
- void (*leave)(void);
- void (*flush)(void);
-} __no_randomize_layout;
-#endif
-
struct pv_cpu_ops {
/* hooks for various privileged instructions */
#ifdef CONFIG_PARAVIRT_XXL
@@ -171,7 +162,7 @@ struct pv_mmu_ops {
void (*set_pgd)(pgd_t *pgdp, pgd_t pgdval);
- struct pv_lazy_ops lazy_mode;
+ void (*lazy_mode_flush)(void);
/* dom0 ops */
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 792fa96b3233..22f72034470f 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -204,11 +204,7 @@ struct paravirt_patch_template pv_ops = {
.mmu.enter_mmap = paravirt_nop,
- .mmu.lazy_mode = {
- .enter = paravirt_nop,
- .leave = paravirt_nop,
- .flush = paravirt_nop,
- },
+ .mmu.lazy_mode_flush = paravirt_nop,
.mmu.set_fixmap = native_set_fixmap,
#endif /* CONFIG_PARAVIRT_XXL */
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 428189f5d437..8ee4910d597a 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -424,9 +424,7 @@ static void xen_start_context_switch(struct task_struct *prev)
{
BUG_ON(preemptible());
- if (this_cpu_read(xen_lazy_mode) == XEN_LAZY_MMU) {
- arch_leave_lazy_mmu_mode();
- }
+ __task_lazy_mmu_mode_pause(prev);
enter_lazy(XEN_LAZY_CPU);
}
@@ -436,8 +434,7 @@ static void xen_end_context_switch(struct task_struct *next)
xen_mc_flush();
leave_lazy(XEN_LAZY_CPU);
- if (__task_lazy_mmu_mode_active(next))
- arch_enter_lazy_mmu_mode();
+ __task_lazy_mmu_mode_resume(next);
}
static unsigned long xen_store_tr(void)
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 51dbdc67c73c..928b4b0a4484 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -324,7 +324,7 @@ static bool xen_batched_set_pte(pte_t *ptep, pte_t pteval)
{
struct mmu_update u;
- if (xen_get_lazy_mode() != XEN_LAZY_MMU)
+ if (!is_lazy_mmu_mode_active())
return false;
xen_mc_batch();
@@ -2151,21 +2151,10 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
#endif
}
-static void xen_enter_lazy_mmu(void)
-{
- preempt_disable();
- if (xen_get_lazy_mode() != XEN_LAZY_MMU)
- enter_lazy(XEN_LAZY_MMU);
- preempt_enable();
-}
-
static void xen_flush_lazy_mmu(void)
{
preempt_disable();
-
- if (xen_get_lazy_mode() == XEN_LAZY_MMU)
- xen_mc_flush();
-
+ xen_mc_flush();
preempt_enable();
}
@@ -2189,15 +2178,6 @@ static void __init xen_post_allocator_init(void)
pv_ops.mmu.write_cr3 = &xen_write_cr3;
}
-static void xen_leave_lazy_mmu(void)
-{
- preempt_disable();
- xen_mc_flush();
- if (xen_get_lazy_mode() != XEN_LAZY_NONE)
- leave_lazy(XEN_LAZY_MMU);
- preempt_enable();
-}
-
void __init xen_init_mmu_ops(void)
{
x86_init.paging.pagetable_init = xen_pagetable_init;
@@ -2237,9 +2217,7 @@ void __init xen_init_mmu_ops(void)
pv_ops.mmu.make_p4d = PV_CALLEE_SAVE(xen_make_p4d);
pv_ops.mmu.enter_mmap = xen_enter_mmap;
pv_ops.mmu.exit_mmap = xen_exit_mmap;
- pv_ops.mmu.lazy_mode.enter = xen_enter_lazy_mmu;
- pv_ops.mmu.lazy_mode.leave = xen_leave_lazy_mmu;
- pv_ops.mmu.lazy_mode.flush = xen_flush_lazy_mmu;
+ pv_ops.mmu.lazy_mode_flush = xen_flush_lazy_mmu;
pv_ops.mmu.set_fixmap = xen_set_fixmap;
memset(dummy_mapping, 0xff, PAGE_SIZE);
--
2.54.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH 0/5] x86/xen: Get rid of Xen private lazy MMU mode tracking
2026-05-26 15:05 [PATCH 0/5] x86/xen: Get rid of Xen private lazy MMU mode tracking Juergen Gross
2026-05-26 15:05 ` [PATCH 4/5] x86/xen: Get rid of last XEN_LAZY_MMU uses Juergen Gross
@ 2026-06-01 15:08 ` David Hildenbrand (Arm)
1 sibling, 0 replies; 3+ messages in thread
From: David Hildenbrand (Arm) @ 2026-06-01 15:08 UTC (permalink / raw)
To: Juergen Gross, linux-kernel, x86, linux-trace-kernel, linux-mm,
virtualization
Cc: Boris Ostrovsky, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, H. Peter Anvin, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, xen-devel, Andrew Morton, Lorenzo Stoakes,
Liam R. Howlett, Vlastimil Babka, Mike Rapoport,
Suren Baghdasaryan, Michal Hocko, Ajay Kaher, Alexey Makhalov,
Broadcom internal kernel review list
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
^ permalink raw reply [flat|nested] 3+ messages in thread