Re: [PATCH v3 19/21] KVM: arm64: Refactor protected nVHE stage-1 locking

Fuad Tabba
2021-08-03T05:31:45Z

Hi Quentin,

On Thu, Jul 29, 2021 at 3:29 PM Quentin Perret <qperret@google.com> wrote:
>
> Refactor the hypervisor stage-1 locking in nVHE protected mode to expose
> a new pkvm_create_mappings_locked() function. This will be used in later
> patches to allow walking and changing the hypervisor stage-1 without
> releasing the lock.
>
> Signed-off-by: Quentin Perret <qperret@google.com>
> ---
> arch/arm64/kvm/hyp/include/nvhe/mm.h | 1 +
> arch/arm64/kvm/hyp/nvhe/mm.c | 18 ++++++++++++++++--
> 2 files changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/mm.h b/arch/arm64/kvm/hyp/include/nvhe/mm.h
> index 8ec3a5a7744b..c76d7136ed9b 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/mm.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/mm.h
> @@ -23,6 +23,7 @@ int hyp_map_vectors(void);
> int hyp_back_vmemmap(phys_addr_t phys, unsigned long size, phys_addr_t back);
> int pkvm_cpu_set_vector(enum arm64_hyp_spectre_vector slot);
> int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot);
> +int pkvm_create_mappings_locked(void *from, void *to, enum kvm_pgtable_prot prot);
> int __pkvm_create_mappings(unsigned long start, unsigned long size,
> unsigned long phys, enum kvm_pgtable_prot prot);
> unsigned long __pkvm_create_private_mapping(phys_addr_t phys, size_t size,
> diff --git a/arch/arm64/kvm/hyp/nvhe/mm.c b/arch/arm64/kvm/hyp/nvhe/mm.c
> index a8efdf0f9003..6fbe8e8030f6 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mm.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mm.c
> @@ -67,13 +67,15 @@ unsigned long __pkvm_create_private_mapping(phys_addr_t phys, size_t size,
> return addr;
> }
>
> -int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
> +int pkvm_create_mappings_locked(void *from, void *to, enum kvm_pgtable_prot prot)
> {
> unsigned long start = (unsigned long)from;
> unsigned long end = (unsigned long)to;
> unsigned long virt_addr;
> phys_addr_t phys;
>
> + hyp_assert_lock_held(&pkvm_pgd_lock);
> +
> start = start & PAGE_MASK;
> end = PAGE_ALIGN(end);
>
> @@ -81,7 +83,8 @@ int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
> int err;
>
> phys = hyp_virt_to_phys((void *)virt_addr);
> - err = __pkvm_create_mappings(virt_addr, PAGE_SIZE, phys, prot);
> + err = kvm_pgtable_hyp_map(&pkvm_pgtable, virt_addr, PAGE_SIZE,
> + phys, prot);
> if (err)
> return err;
> }
> @@ -89,6 +92,17 @@ int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
> return 0;
> }
>
> +int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
> +{
> + int ret;
> +
> + hyp_spin_lock(&pkvm_pgd_lock);
> + ret = pkvm_create_mappings_locked(from, to, prot);
> + hyp_spin_unlock(&pkvm_pgd_lock);
> +
> + return ret;
> +}
> +

I'm wondering whether this patch should also refactor
__pkvm_create_mappings. It doesn't quite do the exact same thing and
has different parameters.

Thanks,
/fuad

> int hyp_back_vmemmap(phys_addr_t phys, unsigned long size, phys_addr_t back)
> {
> unsigned long start, end;
> --
> 2.32.0.432.gabb21c7263-goog
>