linux-kernel - [RFC v2 PATCH 07/13] KVM: Handle page fault for fd based memslot

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 19 Nov 2021 21:47:33 +0800
From:   Chao Peng <chao.p.peng@...ux.intel.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        qemu-devel@...gnu.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, john.ji@...el.com, susie.li@...el.com,
        jun.nakajima@...el.com, dave.hansen@...el.com, ak@...ux.intel.com,
        david@...hat.com
Subject: [RFC v2 PATCH 07/13] KVM: Handle page fault for fd based memslot

Current code assume the private memory is persistent and KVM can check
with backing store to see if private memory exists at the same address
by calling get_pfn(alloc=false).

Signed-off-by: Yu Zhang <yu.c.zhang@...ux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@...ux.intel.com>
---
 arch/x86/kvm/mmu/mmu.c | 75 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 73 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 40377901598b..cd5d1f923694 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3277,6 +3277,9 @@ int kvm_mmu_max_mapping_level(struct kvm *kvm,
 	if (max_level == PG_LEVEL_4K)
 		return PG_LEVEL_4K;
 
+	if (memslot_is_memfd(slot))
+		return max_level;
+
 	host_level = host_pfn_mapping_level(kvm, gfn, pfn, slot);
 	return min(host_level, max_level);
 }
@@ -4555,6 +4558,65 @@ static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 				  kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch);
 }
 
+static bool kvm_faultin_pfn_memfd(struct kvm_vcpu *vcpu,
+				  struct kvm_page_fault *fault, int *r)
+{	int order;
+	kvm_pfn_t pfn;
+	struct kvm_memory_slot *slot = fault->slot;
+	bool priv_gfn = kvm_vcpu_is_private_gfn(vcpu, fault->addr >> PAGE_SHIFT);
+	bool priv_slot_exists = memslot_has_private(slot);
+	bool priv_gfn_exists = false;
+	int mem_convert_type;
+
+	if (priv_gfn && !priv_slot_exists) {
+		*r = RET_PF_INVALID;
+		return true;
+	}
+
+	if (priv_slot_exists) {
+		pfn = slot->memfd_ops->get_pfn(slot, slot->priv_file,
+					       fault->gfn, false, &order);
+		if (pfn >= 0)
+			priv_gfn_exists = true;
+	}
+
+	if (priv_gfn && !priv_gfn_exists) {
+		mem_convert_type = KVM_EXIT_MEM_MAP_PRIVATE;
+		goto out_convert;
+	}
+
+	if (!priv_gfn && priv_gfn_exists) {
+		slot->memfd_ops->put_pfn(pfn);
+		mem_convert_type = KVM_EXIT_MEM_MAP_SHARED;
+		goto out_convert;
+	}
+
+	if (!priv_gfn) {
+		pfn = slot->memfd_ops->get_pfn(slot, slot->file,
+					       fault->gfn, true, &order);
+		if (fault->pfn < 0) {
+			*r = RET_PF_INVALID;
+			return true;
+		}
+	}
+
+	if (slot->flags & KVM_MEM_READONLY)
+		fault->map_writable = false;
+	if (order == 0)
+		fault->max_level = PG_LEVEL_4K;
+
+	return false;
+
+out_convert:
+	vcpu->run->exit_reason = KVM_EXIT_MEMORY_ERROR;
+	vcpu->run->mem.type = mem_convert_type;
+	vcpu->run->mem.u.map.gpa = fault->gfn << PAGE_SHIFT;
+	vcpu->run->mem.u.map.size = PAGE_SIZE;
+	fault->pfn = -1;
+	*r = -1;
+	return true;
+}
+
 static bool kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, int *r)
 {
 	struct kvm_memory_slot *slot = fault->slot;
@@ -4596,6 +4658,9 @@ static bool kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
 		}
 	}
 
+	if (memslot_is_memfd(slot))
+		return kvm_faultin_pfn_memfd(vcpu, fault, r);
+
 	async = false;
 	fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, &async,
 					  fault->write, &fault->map_writable,
@@ -4660,7 +4725,8 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 	else
 		write_lock(&vcpu->kvm->mmu_lock);
 
-	if (fault->slot && mmu_notifier_retry_hva(vcpu->kvm, mmu_seq, fault->hva))
+	if (fault->slot && !memslot_is_memfd(fault->slot) &&
+			mmu_notifier_retry_hva(vcpu->kvm, mmu_seq, fault->hva))
 		goto out_unlock;
 	r = make_mmu_pages_available(vcpu);
 	if (r)
@@ -4676,7 +4742,12 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 		read_unlock(&vcpu->kvm->mmu_lock);
 	else
 		write_unlock(&vcpu->kvm->mmu_lock);
-	kvm_release_pfn_clean(fault->pfn);
+
+	if (memslot_is_memfd(fault->slot))
+		fault->slot->memfd_ops->put_pfn(fault->pfn);
+	else
+		kvm_release_pfn_clean(fault->pfn);
+
 	return r;
 }
 
-- 
2.17.1