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SubjectRe: [PATCH v3 10/10] arm64: ptdump: Add support for guest stage-2 pagetables dumping
On Wed, Nov 15, 2023 at 05:16:40PM +0000, Sebastian Ene wrote:
> +struct ptdump_registered_guest {
> + struct list_head reg_list;
> + struct ptdump_info info;
> + struct kvm_pgtable_snapshot snapshot;
> + rwlock_t *lock;
> +};

Why can't we just store a pointer directly to struct kvm in ::private?
Also, shouldn't you take a reference on struct kvm when the file is
opened to protect against VM teardown?

> +static LIST_HEAD(ptdump_guest_list);
> +static DEFINE_MUTEX(ptdump_list_lock);

What is the list for?

> static phys_addr_t ptdump_host_pa(void *addr)
> {
> return __pa(addr);
> @@ -757,6 +768,63 @@ static void stage2_ptdump_walk(struct seq_file *s, struct ptdump_info *info)
> kvm_pgtable_walk(pgtable, start_ipa, end_ipa, &walker);
> }
>
> +static void guest_stage2_ptdump_walk(struct seq_file *s,
> + struct ptdump_info *info)
> +{
> + struct ptdump_info_file_priv *f_priv =
> + container_of(info, struct ptdump_info_file_priv, info);
> + struct ptdump_registered_guest *guest = info->priv;
> +
> + f_priv->file_priv = &guest->snapshot;
> +
> + read_lock(guest->lock);
> + stage2_ptdump_walk(s, info);
> + read_unlock(guest->lock);

Taking the mmu lock for read allows other table walkers to add new
mappings and adjust the granularity of existing ones. Should this
instead take the mmu lock for write?

> +}
> +
> +int ptdump_register_guest_stage2(struct kvm *kvm)
> +{
> + struct ptdump_registered_guest *guest;
> + struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
> + struct kvm_pgtable *pgt = mmu->pgt;
> +
> + guest = kzalloc(sizeof(struct ptdump_registered_guest), GFP_KERNEL);

You want GFP_KERNEL_ACCOUNT here.

--
Thanks,
Oliver
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