[PATCH v3 02/13] x86/xen: simplify flush_lazy_mmu()

Kevin Brodsky
2025-10-15T08:27:53Z

arch_flush_lazy_mmu_mode() is called when outstanding batched
pgtable operations must be completed immediately. There should
however be no need to leave and re-enter lazy MMU completely. The
only part of that sequence that we really need is xen_mc_flush();
call it directly.

While at it, we can also avoid preempt_disable() if we are not
in lazy MMU mode - xen_get_lazy_mode() should tolerate preemption.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
arch/x86/xen/mmu_pv.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 2a4a8deaf612..dcb7b0989c32 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -2137,14 +2137,11 @@ static void xen_enter_lazy_mmu(void)

static void xen_flush_lazy_mmu(void)
{
- preempt_disable();
-
if (xen_get_lazy_mode() == XEN_LAZY_MMU) {
- arch_leave_lazy_mmu_mode();
- arch_enter_lazy_mmu_mode();
+ preempt_disable();
+ xen_mc_flush();
+ preempt_enable();
}
-
- preempt_enable();
}

static void __init xen_post_allocator_init(void)
--
2.47.0