linux-kernel - [PATCH v3 kvm/queue 04/16] KVM: Extend the memslot to support fd-based private memory

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Date:   Thu, 23 Dec 2021 20:29:59 +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: [PATCH v3 kvm/queue 04/16] KVM: Extend the memslot to support fd-based private memory

Extend the memslot definition to provide fd-based private memory support
by adding two new fields(fd/ofs). The memslot then can maintain memory
for both shared and private pages in a single memslot. Shared pages are
provided in the existing way by using userspace_addr(hva) field and
get_user_pages() while private pages are provided through the new
fields(fd/ofs). Since there is no 'hva' concept anymore for private
memory we cannot call get_user_pages() to get a pfn, instead we rely on
the newly introduced MEMFD_OPS callbacks to do the same job.

This new extension is indicated by a new flag KVM_MEM_PRIVATE.

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 | 10 ++++++++++
 include/uapi/linux/kvm.h | 12 ++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f8ed799e8674..2cd35560c44b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -460,8 +460,18 @@ struct kvm_memory_slot {
 	u32 flags;
 	short id;
 	u16 as_id;
+	u32 fd;
+	struct file *file;
+	u64 ofs;
 };
 
+static inline bool kvm_slot_is_private(const struct kvm_memory_slot *slot)
+{
+	if (slot && (slot->flags & KVM_MEM_PRIVATE))
+		return true;
+	return false;
+}
+
 static inline bool kvm_slot_dirty_track_enabled(const struct kvm_memory_slot *slot)
 {
 	return slot->flags & KVM_MEM_LOG_DIRTY_PAGES;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 1daa45268de2..41434322fa23 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -103,6 +103,17 @@ struct kvm_userspace_memory_region {
 	__u64 userspace_addr; /* start of the userspace allocated memory */
 };
 
+struct kvm_userspace_memory_region_ext {
+	__u32 slot;
+	__u32 flags;
+	__u64 guest_phys_addr;
+	__u64 memory_size; /* bytes */
+	__u64 userspace_addr; /* hva */
+	__u64 ofs; /* offset into fd */
+	__u32 fd;
+	__u32 padding[5];
+};
+
 /*
  * The bit 0 ~ bit 15 of kvm_memory_region::flags are visible for userspace,
  * other bits are reserved for kvm internal use which are defined in
@@ -110,6 +121,7 @@ struct kvm_userspace_memory_region {
  */
 #define KVM_MEM_LOG_DIRTY_PAGES	(1UL << 0)
 #define KVM_MEM_READONLY	(1UL << 1)
+#define KVM_MEM_PRIVATE		(1UL << 2)
 
 /* for KVM_IRQ_LINE */
 struct kvm_irq_level {
-- 
2.17.1