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Message-ID: <ZlekYljG7KJwblUj@google.com>
Date: Wed, 29 May 2024 14:55:46 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: James Houghton <jthoughton@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Paolo Bonzini <pbonzini@...hat.com>,
Albert Ou <aou@...s.berkeley.edu>, Ankit Agrawal <ankita@...dia.com>,
Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>,
Axel Rasmussen <axelrasmussen@...gle.com>, Bibo Mao <maobibo@...ngson.cn>,
Catalin Marinas <catalin.marinas@....com>, David Matlack <dmatlack@...gle.com>,
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James Morse <james.morse@....com>, Jonathan Corbet <corbet@....net>, Marc Zyngier <maz@...nel.org>,
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Oliver Upton <oliver.upton@...ux.dev>, Palmer Dabbelt <palmer@...belt.com>,
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Tianrui Zhao <zhaotianrui@...ngson.cn>, Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
Zenghui Yu <yuzenghui@...wei.com>, kvm-riscv@...ts.infradead.org, kvm@...r.kernel.org,
kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
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Subject: Re: [PATCH v4 4/7] KVM: Move MMU lock acquisition for
test/clear_young to architecture
On Wed, May 29, 2024, James Houghton wrote:
> For implementation mmu_notifier_{test,clear}_young, the KVM memslot
> walker used to take the MMU lock for us. Now make the architectures
> take it themselves.
Hmm, *forcing* architectures to take mmu_lock is a step backwards. Rather than
add all of this churn, what about adding CONFIG_KVM_MMU_NOTIFIER_LOCKLESS, e.g.
static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn,
unsigned long start,
unsigned long end,
gfn_handler_t handler)
{
struct kvm *kvm = mmu_notifier_to_kvm(mn);
const struct kvm_mmu_notifier_range range = {
.start = start,
.end = end,
.handler = handler,
.on_lock = (void *)kvm_null_fn,
.flush_on_ret = false,
.may_block = false,
.lockless = IS_ENABLED(CONFIG_KVM_MMU_NOTIFIER_LOCKLESS),
};
return __kvm_handle_hva_range(kvm, &range).ret;
}
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