[RFC][PATCH] arm64: tlb: call kvm_call_hyp once during kvm_tlb_flush_vmid_range
From: yezhenyu (A) <hidden>
Date: 2026-02-09 13:14:16
Also in:
kvmarm, lkml
Subsystem:
arm64 port (aarch64 architecture), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Catalin Marinas, Will Deacon, Marc Zyngier, Oliver Upton, Linus Torvalds
From 9982be89f55bd99b3683337223284f0011ed248e Mon Sep 17 00:00:00 2001 From: eillon <redacted> Date: Mon, 9 Feb 2026 19:48:46 +0800 Subject: [RFC][PATCH v1] arm64: tlb: call kvm_call_hyp once during kvm_tlb_flush_vmid_range The kvm_tlb_flush_vmid_range() function is performance-critical during live migration, but there is a while loop when the system support flush tlb by range when the size is larger than MAX_TLBI_RANGE_PAGES. This results in frequent entry to kvm_call_hyp() and then a large amount of time is spent in kvm_clear_dirty_log_protect() during migration(more than 50%). So, when the address range is large than MAX_TLBI_RANGE_PAGES, directly call __kvm_tlb_flush_vmid to optimize performance. --- arch/arm64/kvm/hyp/pgtable.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 874244df7..9da22b882 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c@@ -675,21 +675,19 @@ static bool stage2_has_fwb(struct kvm_pgtable *pgt) void kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu, phys_addr_t addr, size_t size) { - unsigned long pages, inval_pages; + unsigned long pages = size >> PAGE_SHIFT; - if (!system_supports_tlb_range()) { + /* + * This function is performance-critical during live migration; + * thus, when the address range is large than MAX_TLBI_RANGE_PAGES, + * directly call __kvm_tlb_flush_vmid to optimize performance. + */ + if (!system_supports_tlb_range() || pages > MAX_TLBI_RANGE_PAGES) { kvm_call_hyp(__kvm_tlb_flush_vmid, mmu); return; } - pages = size >> PAGE_SHIFT; - while (pages > 0) { - inval_pages = min(pages, MAX_TLBI_RANGE_PAGES); - kvm_call_hyp(__kvm_tlb_flush_vmid_range, mmu, addr, inval_pages); - - addr += inval_pages << PAGE_SHIFT; - pages -= inval_pages; - } + kvm_call_hyp(__kvm_tlb_flush_vmid_range, mmu, addr, pages); } #define KVM_S2_MEMATTR(pgt, attr) PAGE_S2_MEMATTR(attr, stage2_has_fwb(pgt)) --
2.43.0