linux-kernel - [RFC v2 PATCH 04/13] KVM: Add fd-based memslot data structure and utils

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Date:   Fri, 19 Nov 2021 21:47:30 +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 04/13] KVM: Add fd-based memslot data structure and utils

For fd-based memslot store the file references for shared fd and the
private fd (if any) in the memslot structure. Since there is no 'hva'
concept we cannot call hva_to_pfn() to get a pfn, instead kvm_memfd_ops
is added to get_pfn/put_pfn from the memory backing stores that provide
these fds.

Signed-off-by: Yu Zhang <yu.c.zhang@...ux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@...ux.intel.com>
---
 include/linux/kvm_host.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 99e9f9969703..1d4ac0c9b63b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -424,6 +424,12 @@ static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu)
  */
 #define KVM_MEM_MAX_NR_PAGES ((1UL << 31) - 1)
 
+struct kvm_memfd_ops {
+	kvm_pfn_t (*get_pfn)(struct kvm_memory_slot *slot, struct file *file,
+			     gfn_t gfn, bool alloc, int *order);
+	void (*put_pfn)(kvm_pfn_t pfn);
+};
+
 struct kvm_memory_slot {
 	gfn_t base_gfn;
 	unsigned long npages;
@@ -433,6 +439,9 @@ struct kvm_memory_slot {
 	u32 flags;
 	short id;
 	u16 as_id;
+	struct file *file;
+	struct file *priv_file;
+	struct kvm_memfd_ops *memfd_ops;
 };
 
 static inline bool kvm_slot_dirty_track_enabled(struct kvm_memory_slot *slot)
@@ -1310,6 +1319,20 @@ static inline int memslot_id(struct kvm *kvm, gfn_t gfn)
 	return gfn_to_memslot(kvm, gfn)->id;
 }
 
+static inline bool memslot_is_memfd(const struct kvm_memory_slot *slot)
+{
+	if (slot && slot->memfd_ops)
+		return true;
+	return false;
+}
+
+static inline bool memslot_has_private(const struct kvm_memory_slot *slot)
+{
+	if (slot && slot->priv_file)
+		return true;
+	return false;
+}
+
 static inline gfn_t
 hva_to_gfn_memslot(unsigned long hva, struct kvm_memory_slot *slot)
 {
-- 
2.17.1