linux-kernel - [RFC v2 PATCH 13/13] KVM: Enable memfd based page invalidation/fallocate

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Date:   Fri, 19 Nov 2021 21:47:39 +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 13/13] KVM: Enable memfd based page invalidation/fallocate

Since the memory backing store does not get notified when VM is
destroyed so need check if VM is still live in these callbacks.

Signed-off-by: Yu Zhang <yu.c.zhang@...ux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@...ux.intel.com>
---
 virt/kvm/memfd.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/virt/kvm/memfd.c b/virt/kvm/memfd.c
index bd930dcb455f..bcfdc685ce22 100644
--- a/virt/kvm/memfd.c
+++ b/virt/kvm/memfd.c
@@ -12,16 +12,38 @@
 #include <linux/memfd.h>
 const static struct guest_mem_ops *memfd_ops;
 
+static bool vm_is_dead(struct kvm *vm)
+{
+	struct kvm *kvm;
+
+	list_for_each_entry(kvm, &vm_list, vm_list) {
+		if (kvm == vm)
+			return false;
+	}
+
+	return true;
+}
+
 static void memfd_invalidate_page_range(struct inode *inode, void *owner,
 					pgoff_t start, pgoff_t end)
 {
 	//!!!We can get here after the owner no longer exists
+	if (vm_is_dead(owner))
+		return;
+
+	kvm_memfd_invalidate_range(owner, inode, start >> PAGE_SHIFT,
+						 end >> PAGE_SHIFT);
 }
 
 static void memfd_fallocate(struct inode *inode, void *owner,
 			    pgoff_t start, pgoff_t end)
 {
 	//!!!We can get here after the owner no longer exists
+	if (vm_is_dead(owner))
+		return;
+
+	kvm_memfd_fallocate_range(owner, inode, start >> PAGE_SHIFT,
+						end >> PAGE_SHIFT);
 }
 
 static const struct guest_ops memfd_notifier = {
-- 
2.17.1