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Message-ID: <20240405115815.3226315-1-pbonzini@redhat.com>
Date: Fri, 5 Apr 2024 07:58:11 -0400
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
kvm@...r.kernel.org
Cc: Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>,
Tianrui Zhao <zhaotianrui@...ngson.cn>,
Bibo Mao <maobibo@...ngson.cn>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Nicholas Piggin <npiggin@...il.com>,
Anup Patel <anup@...infault.org>,
Atish Patra <atishp@...shpatra.org>,
Sean Christopherson <seanjc@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...hat.com>,
linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.linux.dev,
loongarch@...ts.linux.dev,
linux-mips@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org,
kvm-riscv@...ts.infradead.org,
linux-mm@...ck.org,
linux-trace-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org
Subject: [PATCH 0/4] KVM, mm: remove the .change_pte() MMU notifier and set_pte_at_notify()
The .change_pte() MMU notifier callback was intended as an optimization
and for this reason it was initially called without a surrounding
mmu_notifier_invalidate_range_{start,end}() pair. It was only ever
implemented by KVM (which was also the original user of MMU notifiers)
and the rules on when to call set_pte_at_notify() rather than set_pte_at()
have always been pretty obscure.
It may seem a miracle that it has never caused any hard to trigger
bugs, but there's a good reason for that: KVM's implementation has
been nonfunctional for a good part of its existence. Already in
2012, commit 6bdb913f0a70 ("mm: wrap calls to set_pte_at_notify with
invalidate_range_start and invalidate_range_end", 2012-10-09) changed the
change_pte() callback to occur within an invalidate_range_start/end()
pair; and because KVM unmaps the sPTEs during .invalidate_range_start(),
change_pte() has no hope of finding a sPTE to change.
Therefore, all the code for .change_pte() can be removed from both KVM
and mm/, and set_pte_at_notify() can be replaced with just set_pte_at().
Please review! Also feel free to take the KVM patches through the mm
tree, as I don't expect any conflicts.
Thanks,
Paolo
Paolo Bonzini (4):
KVM: delete .change_pte MMU notifier callback
KVM: remove unused argument of kvm_handle_hva_range()
mmu_notifier: remove the .change_pte() callback
mm: replace set_pte_at_notify() with just set_pte_at()
arch/arm64/kvm/mmu.c | 34 -----------------
arch/loongarch/include/asm/kvm_host.h | 1 -
arch/loongarch/kvm/mmu.c | 32 ----------------
arch/mips/kvm/mmu.c | 30 ---------------
arch/powerpc/include/asm/kvm_ppc.h | 1 -
arch/powerpc/kvm/book3s.c | 5 ---
arch/powerpc/kvm/book3s.h | 1 -
arch/powerpc/kvm/book3s_64_mmu_hv.c | 12 ------
arch/powerpc/kvm/book3s_hv.c | 1 -
arch/powerpc/kvm/book3s_pr.c | 7 ----
arch/powerpc/kvm/e500_mmu_host.c | 6 ---
arch/riscv/kvm/mmu.c | 20 ----------
arch/x86/kvm/mmu/mmu.c | 54 +--------------------------
arch/x86/kvm/mmu/spte.c | 16 --------
arch/x86/kvm/mmu/spte.h | 2 -
arch/x86/kvm/mmu/tdp_mmu.c | 46 -----------------------
arch/x86/kvm/mmu/tdp_mmu.h | 1 -
include/linux/kvm_host.h | 2 -
include/linux/mmu_notifier.h | 44 ----------------------
include/trace/events/kvm.h | 15 --------
kernel/events/uprobes.c | 5 +--
mm/ksm.c | 4 +-
mm/memory.c | 7 +---
mm/migrate_device.c | 8 +---
mm/mmu_notifier.c | 17 ---------
virt/kvm/kvm_main.c | 50 +------------------------
26 files changed, 10 insertions(+), 411 deletions(-)
--
2.43.0
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