linux-kernel - [PATCH 4/5] KVM: arm/arm64: Add support for creating PTE contiguous hugepages at stage2

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Date:   Wed, 1 May 2019 09:44:26 +0000
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <linux-kernel@...r.kernel.org>,
        <kvm@...r.kernel.org>
CC:     <marc.zyngier@....com>, <christoffer.dall@....com>,
        <linux@...linux.org.uk>, <catalin.marinas@....com>,
        <will.deacon@....com>, <james.morse@....com>,
        <julien.thierry@....com>, <suzuki.poulose@....com>,
        <steve.capper@....com>, <wanghaibin.wang@...wei.com>,
        Zenghui Yu <yuzenghui@...wei.com>
Subject: [PATCH 4/5] KVM: arm/arm64: Add support for creating PTE contiguous hugepages at stage2

Extend the stage2 fault handling to map in PTE contiguous hugepages first.
With this patch, we now support additional following page size at stage2:

                CONT PTE
                --------
 4K granule:      64K
16K granule:       2M
64K granule:       2M

The PMD contiguous huge mapping is still not supported yet and will be
simply fall back to a PTE mapping.

Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
---
 virt/kvm/arm/mmu.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 75 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 36c863f..fdd6314 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1104,6 +1104,27 @@ static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memory_cache *cache
 	return stage2_pmd_offset(kvm, pud, addr);
 }
 
+static pte_t *stage2_get_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
+			     phys_addr_t addr)
+{
+	pmd_t *pmd;
+	pte_t *pte;
+
+	pmd = stage2_get_pmd(kvm, cache, addr);
+	if (!pmd || pmd_thp_or_huge(*pmd))
+		return NULL;
+
+	if (pmd_none(*pmd)) {
+		if (!cache)
+			return NULL;
+		pte = mmu_memory_cache_alloc(cache);
+		kvm_pmd_populate(pmd, pte);
+		get_page(virt_to_page(pmd));
+	}
+
+	return pte_offset_kernel(pmd, addr);
+}
+
 static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
 			       *cache, phys_addr_t addr, const pmd_t *new_pmd)
 {
@@ -1270,6 +1291,54 @@ static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr)
 		return kvm_s2pte_exec(ptep);
 }
 
+/* This code is borrowed from arch/arm64/mm/hugetlbpage.c */
+static inline pgprot_t pte_pgprot(pte_t pte)
+{
+	unsigned long pfn = pte_pfn(pte);
+
+	return __pgprot(pte_val(pfn_pte(pfn, __pgprot(0))) ^ pte_val(pte));
+}
+
+static int stage2_set_cont_ptes(struct kvm *kvm, struct kvm_mmu_memory_cache
+				*cache, phys_addr_t addr, const pte_t *new_pte)
+{
+	pte_t *pte, old_pte;
+	unsigned long pfn, dpfn;
+	int i;
+	pgprot_t hugeprot;
+
+	/*
+	 * Make sure we start manipulating the first pte
+	 * within CONT_PTES ptes.
+	 */
+	addr &= CONT_PTE_MASK;
+	pfn = pte_pfn(*new_pte);
+	dpfn = PAGE_SIZE >> PAGE_SHIFT;
+	hugeprot = pte_pgprot(*new_pte);
+
+	pte = stage2_get_pte(kvm, cache, addr);
+	VM_BUG_ON(!pte);
+
+	old_pte = *pte;
+
+	/* Skip page table update if there is no change */
+	if (pte_val(old_pte) == pte_val(*new_pte))
+		return 0;
+
+	for (i = 0; i < CONT_PTES; i++, pte++, addr += PAGE_SIZE, pfn += dpfn) {
+		if (pte_present(old_pte)) {
+			kvm_set_pte(pte, __pte(0));
+			kvm_tlb_flush_vmid_ipa(kvm, addr);
+		} else {
+			get_page(virt_to_page(pte));
+		}
+
+		kvm_set_pte(pte, kvm_pfn_pte(pfn, hugeprot));
+	}
+
+	return 0;
+}
+
 static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
 			  phys_addr_t addr, const pte_t *new_pte,
 			  unsigned long flags)
@@ -1824,7 +1893,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * As for PUD huge maps, we must make sure that we have at least
 	 * 3 levels, i.e, PMD is not folded.
 	 */
-	if (vma_pagesize == PMD_SIZE ||
+	if (vma_pagesize == CONT_PTE_SIZE || vma_pagesize == PMD_SIZE ||
 	    (vma_pagesize == PUD_SIZE && kvm_stage2_has_pmd(kvm)))
 		gfn = (fault_ipa & huge_page_mask(hstate_vma(vma))) >> PAGE_SHIFT;
 	up_read(&current->mm->mmap_sem);
@@ -1918,6 +1987,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 						 needs_exec, false);
 
 		ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
+	} else if (vma_pagesize == CONT_PTE_SIZE) {
+		pte_t new_pte = stage2_build_pte(pfn, mem_type, writable,
+						 needs_exec, true);
+
+		ret = stage2_set_cont_ptes(kvm, memcache, fault_ipa, &new_pte);
 	} else {
 		pte_t new_pte = stage2_build_pte(pfn, mem_type, writable,
 						 needs_exec, false);
-- 
1.8.3.1