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[PATCH v5 08/13] KVM: Use memfile_pfn_ops to obtain pfn for private page
From: |
Chao Peng |
Subject: |
[PATCH v5 08/13] KVM: Use memfile_pfn_ops to obtain pfn for private pages |
Date: |
Thu, 10 Mar 2022 22:09:06 +0800 |
Private pages are not mmap-ed into userspace so can not reply on
get_user_pages() to obtain the pfn. Instead we add a memfile_pfn_ops
pointer pfn_ops in each private memslot and use it to obtain the pfn
for a gfn. To do that, KVM should convert the gfn to the offset into
the fd and then call get_lock_pfn callback. Once KVM completes its job
it should call put_unlock_pfn to unlock the pfn. Note the pfn(page) is
locked between get_lock_pfn/put_unlock_pfn to ensure pfn is valid when
KVM uses it to establish the mapping in the secondary MMU page table.
The pfn_ops is initialized via memfile_register_notifier from the memory
backing store that provided the private_fd.
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
arch/x86/kvm/Kconfig | 1 +
include/linux/kvm_host.h | 33 +++++++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index e3cbd7706136..ca7b2a6a452a 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -48,6 +48,7 @@ config KVM
select SRCU
select INTERVAL_TREE
select HAVE_KVM_PM_NOTIFIER if PM
+ select MEMFILE_NOTIFIER
help
Support hosting fully virtualized guest machines using hardware
virtualization extensions. You will need a fairly recent
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c92c70174248..6e1d770d6bf8 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -44,6 +44,7 @@
#include <asm/kvm_host.h>
#include <linux/kvm_dirty_ring.h>
+#include <linux/memfile_notifier.h>
#ifndef KVM_MAX_VCPU_IDS
#define KVM_MAX_VCPU_IDS KVM_MAX_VCPUS
@@ -565,6 +566,7 @@ struct kvm_memory_slot {
u16 as_id;
struct file *private_file;
loff_t private_offset;
+ struct memfile_pfn_ops *pfn_ops;
};
static inline bool kvm_slot_is_private(const struct kvm_memory_slot *slot)
@@ -915,6 +917,7 @@ static inline void kvm_irqfd_exit(void)
{
}
#endif
+
int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
struct module *module);
void kvm_exit(void);
@@ -2217,4 +2220,34 @@ static inline void kvm_handle_signal_exit(struct
kvm_vcpu *vcpu)
/* Max number of entries allowed for each kvm dirty ring */
#define KVM_DIRTY_RING_MAX_ENTRIES 65536
+#ifdef CONFIG_MEMFILE_NOTIFIER
+static inline long kvm_memfile_get_pfn(struct kvm_memory_slot *slot, gfn_t gfn,
+ int *order)
+{
+ pgoff_t index = gfn - slot->base_gfn +
+ (slot->private_offset >> PAGE_SHIFT);
+
+ return slot->pfn_ops->get_lock_pfn(file_inode(slot->private_file),
+ index, order);
+}
+
+static inline void kvm_memfile_put_pfn(struct kvm_memory_slot *slot,
+ kvm_pfn_t pfn)
+{
+ slot->pfn_ops->put_unlock_pfn(pfn);
+}
+
+#else
+static inline long kvm_memfile_get_pfn(struct kvm_memory_slot *slot, gfn_t gfn,
+ int *order)
+{
+ return -1;
+}
+
+static inline void kvm_memfile_put_pfn(struct kvm_memory_slot *slot,
+ kvm_pfn_t pfn)
+{
+}
+#endif /* CONFIG_MEMFILE_NOTIFIER */
+
#endif
--
2.17.1
- Re: [PATCH v5 03/13] mm/shmem: Support memfile_notifier, (continued)
- [PATCH v5 04/13] mm/shmem: Restrict MFD_INACCESSIBLE memory against RLIMIT_MEMLOCK, Chao Peng, 2022/03/10
- [PATCH v5 05/13] KVM: Extend the memslot to support fd-based private memory, Chao Peng, 2022/03/10
- [PATCH v5 06/13] KVM: Use kvm_userspace_memory_region_ext, Chao Peng, 2022/03/10
- [PATCH v5 07/13] KVM: Add KVM_EXIT_MEMORY_ERROR exit, Chao Peng, 2022/03/10
- [PATCH v5 08/13] KVM: Use memfile_pfn_ops to obtain pfn for private pages,
Chao Peng <=
- [PATCH v5 10/13] KVM: Register private memslot to memory backing store, Chao Peng, 2022/03/10
- [PATCH v5 09/13] KVM: Handle page fault for private memory, Chao Peng, 2022/03/10
- [PATCH v5 12/13] KVM: Expose KVM_MEM_PRIVATE, Chao Peng, 2022/03/10
- [PATCH v5 11/13] KVM: Zap existing KVM mappings when pages changed in the private fd, Chao Peng, 2022/03/10
- [PATCH v5 13/13] memfd_create.2: Describe MFD_INACCESSIBLE flag, Chao Peng, 2022/03/10