[PATCH v4 04/13] KVM: x86: Move n_memslots_pages recalc to kvm_arch_prepare_memory_region()

From: Maciej S. Szmigiero
Date: Fri Aug 13 2021 - 16:01:31 EST


From: "Maciej S. Szmigiero" <maciej.szmigiero@xxxxxxxxxx>

This allows us to return a proper error code in case we spot an underflow.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 43 +++++++++++++++++++++++++------------------
1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2ab0de7483ef..f39bf3c3a054 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11490,9 +11490,23 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
const struct kvm_userspace_memory_region *mem,
enum kvm_mr_change change)
{
- if (change == KVM_MR_CREATE || change == KVM_MR_MOVE)
- return kvm_alloc_memslot_metadata(kvm, new,
- mem->memory_size >> PAGE_SHIFT);
+ if (change == KVM_MR_CREATE || change == KVM_MR_MOVE) {
+ int ret;
+
+ ret = kvm_alloc_memslot_metadata(kvm, new,
+ mem->memory_size >> PAGE_SHIFT);
+ if (ret)
+ return ret;
+
+ if (change == KVM_MR_CREATE)
+ kvm->arch.n_memslots_pages += new->npages;
+ } else if (change == KVM_MR_DELETE) {
+ if (WARN_ON(kvm->arch.n_memslots_pages < old->npages))
+ return -EIO;
+
+ kvm->arch.n_memslots_pages -= old->npages;
+ }
+
return 0;
}

@@ -11589,22 +11603,15 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
const struct kvm_memory_slot *new,
enum kvm_mr_change change)
{
- if (change == KVM_MR_CREATE || change == KVM_MR_DELETE) {
- if (change == KVM_MR_CREATE)
- kvm->arch.n_memslots_pages += new->npages;
- else {
- WARN_ON(kvm->arch.n_memslots_pages < old->npages);
- kvm->arch.n_memslots_pages -= old->npages;
- }
-
- if (!kvm->arch.n_requested_mmu_pages) {
- unsigned long nr_mmu_pages;
+ /* Only CREATE or DELETE affects n_memslots_pages */
+ if ((change == KVM_MR_CREATE || change == KVM_MR_DELETE) &&
+ !kvm->arch.n_requested_mmu_pages) {
+ unsigned long nr_mmu_pages;

- nr_mmu_pages = kvm->arch.n_memslots_pages *
- KVM_PERMILLE_MMU_PAGES / 1000;
- nr_mmu_pages = max(nr_mmu_pages, KVM_MIN_ALLOC_MMU_PAGES);
- kvm_mmu_change_mmu_pages(kvm, nr_mmu_pages);
- }
+ nr_mmu_pages = kvm->arch.n_memslots_pages *
+ KVM_PERMILLE_MMU_PAGES / 1000;
+ nr_mmu_pages = max(nr_mmu_pages, KVM_MIN_ALLOC_MMU_PAGES);
+ kvm_mmu_change_mmu_pages(kvm, nr_mmu_pages);
}

kvm_mmu_slot_apply_flags(kvm, old, new, change);