[PATCH v2 0/6] KVM: Remove kvm_is_transparent_hugepage() and friends

From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, linux-mm@kvack.org
Cc: Sean Christopherson <seanjc@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Will Deacon <will@kernel.org>,
	Quentin Perret <qperret@google.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	kernel-team@android.com
Subject: [PATCH v2 0/6] KVM: Remove kvm_is_transparent_hugepage() and friends
Date: Mon, 26 Jul 2021 16:35:46 +0100	[thread overview]
Message-ID: <20210726153552.1535838-1-maz@kernel.org> (raw)

A while ago, Willy and Sean pointed out[0] that arm64 is the last user
of kvm_is_transparent_hugepage(), and that there would actually be
some benefit in looking at the userspace mapping directly instead.

This small series does exactly that, although it doesn't try to
support more than a PMD-sized mapping yet for THPs. We could probably
look into unifying this with the huge PUD code, and there is still
some potential use of the contiguous hint.

As a consequence, it removes kvm_is_transparent_hugepage(),
PageTransCompoundMap() and kvm_get_pfn(), all of which have no user
left after this rework.

This has been lightly tested on an Altra box (VHE) and on a SC2A11
system (nVHE). Although nothing caught fire, it requires some careful
reviewing on the arm64 side.

* From v1 [1]:

  - Move the PT helper into its own function, as both Quentin and I
    need it for other developments
  - Fixed stupid bug introduced by a bad conflict resolution, spotted
    by Alexandru
  - Collected Acks from Paolo, with thanks

[0] https://lore.kernel.org/r/YLpLvFPXrIp8nAK4@google.com
[1] https://lore.kernel.org/r/20210717095541.1486210-1-maz@kernel.org

Marc Zyngier (6):
  KVM: arm64: Introduce helper to retrieve a PTE and its level
  KVM: arm64: Walk userspace page tables to compute the THP mapping size
  KVM: arm64: Avoid mapping size adjustment on permission fault
  KVM: Remove kvm_is_transparent_hugepage() and PageTransCompoundMap()
  KVM: arm64: Use get_page() instead of kvm_get_pfn()
  KVM: Get rid of kvm_get_pfn()

 arch/arm64/include/asm/kvm_pgtable.h | 19 ++++++++++++
 arch/arm64/kvm/hyp/pgtable.c         | 39 ++++++++++++++++++++++++
 arch/arm64/kvm/mmu.c                 | 45 +++++++++++++++++++++++-----
 include/linux/kvm_host.h             |  1 -
 include/linux/page-flags.h           | 37 -----------------------
 virt/kvm/kvm_main.c                  | 19 +-----------
 6 files changed, 97 insertions(+), 63 deletions(-)

-- 
2.30.2

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