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// SPDX-License-Identifier: GPL-2.0-only
/*
* KVM dirty ring implementation
*
* Copyright 2019 Red Hat, Inc.
*/
#include <linux/kvm_host.h>
#include <linux/kvm.h>
#include <linux/vmalloc.h>
#include <linux/kvm_dirty_ring.h>
#include <trace/events/kvm.h>
#include "kvm_mm.h"
int __weak kvm_cpu_dirty_log_size(void)
{
return 0;
}
u32 kvm_dirty_ring_get_rsvd_entries(void)
{
return KVM_DIRTY_RING_RSVD_ENTRIES + kvm_cpu_dirty_log_size();
}
bool kvm_use_dirty_bitmap(struct kvm *kvm)
{
lockdep_assert_held(&kvm->slots_lock);
return !kvm->dirty_ring_size || kvm->dirty_ring_with_bitmap;
}
#ifndef CONFIG_NEED_KVM_DIRTY_RING_WITH_BITMAP
bool kvm_arch_allow_write_without_running_vcpu(struct kvm *kvm)
{
return false;
}
#endif
static u32 kvm_dirty_ring_used(struct kvm_dirty_ring *ring)
{
return READ_ONCE(ring->dirty_index) - READ_ONCE(ring->reset_index);
}
static bool kvm_dirty_ring_soft_full(struct kvm_dirty_ring *ring)
{
return kvm_dirty_ring_used(ring) >= ring->soft_limit;
}
static bool kvm_dirty_ring_full(struct kvm_dirty_ring *ring)
{
return kvm_dirty_ring_used(ring) >= ring->size;
}
static void kvm_reset_dirty_gfn(struct kvm *kvm, u32 slot, u64 offset, u64 mask)
{
struct kvm_memory_slot *memslot;
int as_id, id;
as_id = slot >> 16;
id = (u16)slot;
if (as_id >= kvm_arch_nr_memslot_as_ids(kvm) || id >= KVM_USER_MEM_SLOTS)
return;
memslot = id_to_memslot(__kvm_memslots(kvm, as_id), id);
if (!memslot || (offset + __fls(mask)) >= memslot->npages)
return;
KVM_MMU_LOCK(kvm);
kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot, offset, mask);
KVM_MMU_UNLOCK(kvm);
}
int kvm_dirty_ring_alloc(struct kvm_dirty_ring *ring, int index, u32 size)
{
ring->dirty_gfns = vzalloc(size);
if (!ring->dirty_gfns)
return -ENOMEM;
ring->size = size / sizeof(struct kvm_dirty_gfn);
ring->soft_limit = ring->size - kvm_dirty_ring_get_rsvd_entries();
ring->dirty_index = 0;
ring->reset_index = 0;
ring->index = index;
return 0;
}
static inline void kvm_dirty_gfn_set_invalid(struct kvm_dirty_gfn *gfn)
{
smp_store_release(&gfn->flags, 0);
}
static inline void kvm_dirty_gfn_set_dirtied(struct kvm_dirty_gfn *gfn)
{
gfn->flags = KVM_DIRTY_GFN_F_DIRTY;
}
static inline bool kvm_dirty_gfn_harvested(struct kvm_dirty_gfn *gfn)
{
return smp_load_acquire(&gfn->flags) & KVM_DIRTY_GFN_F_RESET;
}
int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_dirty_ring *ring)
{
u32 cur_slot, next_slot;
u64 cur_offset, next_offset;
unsigned long mask;
int count = 0;
struct kvm_dirty_gfn *entry;
bool first_round = true;
/* This is only needed to make compilers happy */
cur_slot = cur_offset = mask = 0;
while (true) {
entry = &ring->dirty_gfns[ring->reset_index & (ring->size - 1)];
if (!kvm_dirty_gfn_harvested(entry))
break;
next_slot = READ_ONCE(entry->slot);
next_offset = READ_ONCE(entry->offset);
/* Update the flags to reflect that this GFN is reset */
kvm_dirty_gfn_set_invalid(entry);
ring->reset_index++;
count++;
/*
* Try to coalesce the reset operations when the guest is
* scanning pages in the same slot.
*/
if (!first_round && next_slot == cur_slot) {
s64 delta = next_offset - cur_offset;
if (delta >= 0 && delta < BITS_PER_LONG) {
mask |= 1ull << delta;
continue;
}
/* Backwards visit, careful about overflows! */
if (delta > -BITS_PER_LONG && delta < 0 &&
(mask << -delta >> -delta) == mask) {
cur_offset = next_offset;
mask = (mask << -delta) | 1;
continue;
}
}
kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask);
cur_slot = next_slot;
cur_offset = next_offset;
mask = 1;
first_round = false;
}
kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask);
/*
* The request KVM_REQ_DIRTY_RING_SOFT_FULL will be cleared
* by the VCPU thread next time when it enters the guest.
*/
trace_kvm_dirty_ring_reset(ring);
return count;
}
void kvm_dirty_ring_push(struct kvm_vcpu *vcpu, u32 slot, u64 offset)
{
struct kvm_dirty_ring *ring = &vcpu->dirty_ring;
struct kvm_dirty_gfn *entry;
/* It should never get full */
WARN_ON_ONCE(kvm_dirty_ring_full(ring));
entry = &ring->dirty_gfns[ring->dirty_index & (ring->size - 1)];
entry->slot = slot;
entry->offset = offset;
/*
* Make sure the data is filled in before we publish this to
* the userspace program. There's no paired kernel-side reader.
*/
smp_wmb();
kvm_dirty_gfn_set_dirtied(entry);
ring->dirty_index++;
trace_kvm_dirty_ring_push(ring, slot, offset);
if (kvm_dirty_ring_soft_full(ring))
kvm_make_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu);
}
bool kvm_dirty_ring_check_request(struct kvm_vcpu *vcpu)
{
/*
* The VCPU isn't runnable when the dirty ring becomes soft full.
* The KVM_REQ_DIRTY_RING_SOFT_FULL event is always set to prevent
* the VCPU from running until the dirty pages are harvested and
* the dirty ring is reset by userspace.
*/
if (kvm_check_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu) &&
kvm_dirty_ring_soft_full(&vcpu->dirty_ring)) {
kvm_make_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu);
vcpu->run->exit_reason = KVM_EXIT_DIRTY_RING_FULL;
trace_kvm_dirty_ring_exit(vcpu);
return true;
}
return false;
}
struct page *kvm_dirty_ring_get_page(struct kvm_dirty_ring *ring, u32 offset)
{
return vmalloc_to_page((void *)ring->dirty_gfns + offset * PAGE_SIZE);
}
void kvm_dirty_ring_free(struct kvm_dirty_ring *ring)
{
vfree(ring->dirty_gfns);
ring->dirty_gfns = NULL;
}
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