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author | Maciej S. Szmigiero <maciej.szmigiero@oracle.com> | 2021-12-06 20:54:09 +0100 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-12-08 04:24:18 -0500 |
commit | 4e4d30cb9b8740e178731406aa28b96f12c6edbd (patch) | |
tree | 3eefa59d61b04d4c497146d1dda62004273279be | |
parent | 47ea7d900b1cc66ec7a35a8b173ed16b01f9781b (diff) | |
download | linux-4e4d30cb9b8740e178731406aa28b96f12c6edbd.tar.bz2 |
KVM: Resync only arch fields when slots_arch_lock gets reacquired
There is no need to copy the whole memslot data after releasing
slots_arch_lock for a moment to install temporary memslots copy in
kvm_set_memslot() since this lock only protects the arch field of each
memslot.
Just resync this particular field after reacquiring slots_arch_lock.
Note, this also eliminates the need to manually clear the INVALID flag
when restoring memslots; the "setting" of the INVALID flag was an
unwanted side effect of copying the entire memslots.
Since kvm_copy_memslots() has just one caller remaining now
open-code it instead.
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
[sean: tweak shortlog, note INVALID flag in changelog, revert comment]
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <b63035d114707792e9042f074478337f770dff6a.1638817638.git.maciej.szmigiero@oracle.com>
-rw-r--r-- | virt/kvm/kvm_main.c | 45 |
1 files changed, 25 insertions, 20 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index af2730858ebd..615d69bcde2c 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1515,12 +1515,6 @@ static size_t kvm_memslots_size(int slots) (sizeof(struct kvm_memory_slot) * slots); } -static void kvm_copy_memslots(struct kvm_memslots *to, - struct kvm_memslots *from) -{ - memcpy(to, from, kvm_memslots_size(from->used_slots)); -} - /* * Note, at a minimum, the current number of used slots must be allocated, even * when deleting a memslot, as we need a complete duplicate of the memslots for @@ -1539,11 +1533,22 @@ static struct kvm_memslots *kvm_dup_memslots(struct kvm_memslots *old, slots = kvzalloc(new_size, GFP_KERNEL_ACCOUNT); if (likely(slots)) - kvm_copy_memslots(slots, old); + memcpy(slots, old, kvm_memslots_size(old->used_slots)); return slots; } +static void kvm_copy_memslots_arch(struct kvm_memslots *to, + struct kvm_memslots *from) +{ + int i; + + WARN_ON_ONCE(to->used_slots != from->used_slots); + + for (i = 0; i < from->used_slots; i++) + to->memslots[i].arch = from->memslots[i].arch; +} + static int kvm_set_memslot(struct kvm *kvm, const struct kvm_userspace_memory_region *mem, struct kvm_memory_slot *new, int as_id, @@ -1584,9 +1589,10 @@ static int kvm_set_memslot(struct kvm *kvm, slot->flags |= KVM_MEMSLOT_INVALID; /* - * We can re-use the memory from the old memslots. - * It will be overwritten with a copy of the new memslots - * after reacquiring the slots_arch_lock below. + * We can re-use the old memslots, the only difference from the + * newly installed memslots is the invalid flag, which will get + * dropped by update_memslots anyway. We'll also revert to the + * old memslots if preparing the new memory region fails. */ slots = install_new_memslots(kvm, as_id, slots); @@ -1603,12 +1609,14 @@ static int kvm_set_memslot(struct kvm *kvm, mutex_lock(&kvm->slots_arch_lock); /* - * The arch-specific fields of the memslots could have changed - * between releasing the slots_arch_lock in - * install_new_memslots and here, so get a fresh copy of the - * slots. + * The arch-specific fields of the now-active memslots could + * have been modified between releasing slots_arch_lock in + * install_new_memslots and re-acquiring slots_arch_lock above. + * Copy them to the inactive memslots. Arch code is required + * to retrieve memslots *after* acquiring slots_arch_lock, thus + * the active memslots are guaranteed to be fresh. */ - kvm_copy_memslots(slots, __kvm_memslots(kvm, as_id)); + kvm_copy_memslots_arch(slots, __kvm_memslots(kvm, as_id)); } /* @@ -1657,13 +1665,10 @@ static int kvm_set_memslot(struct kvm *kvm, return 0; out_slots: - if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) { - slot = id_to_memslot(slots, new->id); - slot->flags &= ~KVM_MEMSLOT_INVALID; + if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) slots = install_new_memslots(kvm, as_id, slots); - } else { + else mutex_unlock(&kvm->slots_arch_lock); - } kvfree(slots); return r; } |