On Mon, 22 Nov 2021 09:58:03 +0000,
Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Commit 1776c91346b6 ("KVM: arm64: nv: Support multiple nested Stage-2 mmu
> structures")[1] added a function kvm_vcpu_init_nested which expands the
> stage-2 mmu structures array when ever a new vCPU is created. The array
> is expanded using krealloc() and results in a stale mmu address pointer
> in pgt->mmu. Adding a fix to update the pointer with the new address after
> successful krealloc.
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/
> branch kvm-arm64/nv-5.13
>
> Signed-off-by: Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx>
> ---
> arch/arm64/kvm/nested.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
> index 4ffbc14d0245..57ad8d8f4ee5 100644
> --- a/arch/arm64/kvm/nested.c
> +++ b/arch/arm64/kvm/nested.c
> @@ -68,6 +68,8 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
> num_mmus * sizeof(*kvm->arch.nested_mmus),
> GFP_KERNEL | __GFP_ZERO);
> if (tmp) {
> + int i;
> +
> if (kvm_init_stage2_mmu(kvm, &tmp[num_mmus - 1]) ||
> kvm_init_stage2_mmu(kvm, &tmp[num_mmus - 2])) {
> kvm_free_stage2_pgd(&tmp[num_mmus - 1]);
> @@ -80,6 +82,13 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
> }
>
> kvm->arch.nested_mmus = tmp;
> +
> + /* Fixup pgt->mmu after krealloc */
> + for (i = 0; i < kvm->arch.nested_mmus_size; i++) {
> + struct kvm_s2_mmu *mmu = &kvm->arch.nested_mmus[i];
> +
> + mmu->pgt->mmu = mmu;
> + }
> }
>
> mutex_unlock(&kvm->lock);
Another good catch. I've tweaked a bit to avoid some unnecessary
repainting, see below.
Thanks again,
M.
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index a4dfffa1dae0..92b225db59ac 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -66,8 +66,19 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
num_mmus = atomic_read(&kvm->online_vcpus) * 2;
tmp = krealloc(kvm->arch.nested_mmus,
num_mmus * sizeof(*kvm->arch.nested_mmus),
- GFP_KERNEL | __GFP_ZERO);
+ GFP_KERNEL_ACCOUNT | __GFP_ZERO);
if (tmp) {
+ /*
+ * If we went through a realocation, adjust the MMU
+ * back-pointers in the pg_table structures.
+ */
+ if (kvm->arch.nested_mmus != tmp) {
+ int i;
+
+ for (i = 0; i < num_mms - 2; i++)
+ tmp[i].pgt->mmu = &tmp[i];
+ }
+
if (kvm_init_stage2_mmu(kvm, &tmp[num_mmus - 1]) ||
kvm_init_stage2_mmu(kvm, &tmp[num_mmus - 2])) {
kvm_free_stage2_pgd(&tmp[num_mmus - 1]);
--
Without deviation from the norm, progress is not possible.
