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

Quentin Perret
2021-08-03T10:37:14Z

Hey Fuad,

On Tuesday 03 Aug 2021 at 07:31:03 (+0200), Fuad Tabba wrote:
> 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.

Sorry, not sure I'm understanding your suggestion here. What do you
think should be done to __pkvm_create_mappings?

Cheers,
Quentin