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 2/6] KVM: arm64: Walk userspace page tables to compute the THP mapping size
Date: Mon, 26 Jul 2021 16:35:48 +0100 [thread overview]
Message-ID: <20210726153552.1535838-3-maz@kernel.org> (raw)
In-Reply-To: <20210726153552.1535838-1-maz@kernel.org>
We currently rely on the kvm_is_transparent_hugepage() helper to
discover whether a given page has the potential to be mapped as
a block mapping.
However, this API doesn't really give un everything we want:
- we don't get the size: this is not crucial today as we only
support PMD-sized THPs, but we'd like to have larger sizes
in the future
- we're the only user left of the API, and there is a will
to remove it altogether
To address the above, implement a simple walker using the existing
page table infrastructure, and plumb it into transparent_hugepage_adjust().
No new page sizes are supported in the process.
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/mmu.c | 34 ++++++++++++++++++++++++++++++----
1 file changed, 30 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 3155c9e778f0..0adc1617c557 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -433,6 +433,32 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
return 0;
}
+static struct kvm_pgtable_mm_ops kvm_user_mm_ops = {
+ /* We shouldn't need any other callback to walk the PT */
+ .phys_to_virt = kvm_host_va,
+};
+
+static int get_user_mapping_size(struct kvm *kvm, u64 addr)
+{
+ struct kvm_pgtable pgt = {
+ .pgd = (kvm_pte_t *)kvm->mm->pgd,
+ .ia_bits = VA_BITS,
+ .start_level = (KVM_PGTABLE_MAX_LEVELS -
+ CONFIG_PGTABLE_LEVELS),
+ .mm_ops = &kvm_user_mm_ops,
+ };
+ kvm_pte_t pte = 0; /* Keep GCC quiet... */
+ u32 level = ~0;
+ int ret;
+
+ ret = kvm_pgtable_get_leaf(&pgt, addr, &pte, &level);
+ VM_BUG_ON(ret);
+ VM_BUG_ON(level >= KVM_PGTABLE_MAX_LEVELS);
+ VM_BUG_ON(!(pte & PTE_VALID));
+
+ return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(level));
+}
+
static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {
.zalloc_page = stage2_memcache_zalloc_page,
.zalloc_pages_exact = kvm_host_zalloc_pages_exact,
@@ -780,7 +806,7 @@ static bool fault_supports_stage2_huge_mapping(struct kvm_memory_slot *memslot,
* Returns the size of the mapping.
*/
static unsigned long
-transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
+transparent_hugepage_adjust(struct kvm *kvm, struct kvm_memory_slot *memslot,
unsigned long hva, kvm_pfn_t *pfnp,
phys_addr_t *ipap)
{
@@ -791,8 +817,8 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
* sure that the HVA and IPA are sufficiently aligned and that the
* block map is contained within the memslot.
*/
- if (kvm_is_transparent_hugepage(pfn) &&
- fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
+ if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE) &&
+ get_user_mapping_size(kvm, hva) >= PMD_SIZE) {
/*
* The address we faulted on is backed by a transparent huge
* page. However, because we map the compound huge page and
@@ -1051,7 +1077,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
* backed by a THP and thus use block mapping if possible.
*/
if (vma_pagesize == PAGE_SIZE && !(force_pte || device))
- vma_pagesize = transparent_hugepage_adjust(memslot, hva,
+ vma_pagesize = transparent_hugepage_adjust(kvm, memslot, hva,
&pfn, &fault_ipa);
if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
--
2.30.2
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next prev parent reply other threads:[~2021-07-26 15:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-26 15:35 [PATCH v2 0/6] KVM: Remove kvm_is_transparent_hugepage() and friends Marc Zyngier
2021-07-26 15:35 ` [PATCH v2 1/6] KVM: arm64: Introduce helper to retrieve a PTE and its level Marc Zyngier
2021-07-27 10:29 ` Quentin Perret
2021-07-27 15:25 ` Alexandru Elisei
2021-07-28 12:17 ` Marc Zyngier
2021-07-26 15:35 ` Marc Zyngier [this message]
2021-07-27 15:55 ` [PATCH v2 2/6] KVM: arm64: Walk userspace page tables to compute the THP mapping size Alexandru Elisei
2021-07-26 15:35 ` [PATCH v2 3/6] KVM: arm64: Avoid mapping size adjustment on permission fault Marc Zyngier
2021-07-27 16:00 ` Alexandru Elisei
2021-07-26 15:35 ` [PATCH v2 4/6] KVM: Remove kvm_is_transparent_hugepage() and PageTransCompoundMap() Marc Zyngier
2021-07-26 15:35 ` [PATCH v2 5/6] KVM: arm64: Use get_page() instead of kvm_get_pfn() Marc Zyngier
2021-07-27 17:46 ` Alexandru Elisei
2021-07-26 15:35 ` [PATCH v2 6/6] KVM: Get rid " Marc Zyngier
2021-08-02 13:39 ` [PATCH v2 0/6] KVM: Remove kvm_is_transparent_hugepage() and friends Marc Zyngier
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