On Mon, Apr 17, 2023 at 02:18:26PM +0800, Gavin Shan wrote:
> On 4/9/23 2:29 PM, Ricardo Koller wrote:
> > Add a stage2 helper, kvm_pgtable_stage2_create_unlinked(), for
> > creating unlinked tables (which is the opposite of
> > kvm_pgtable_stage2_free_unlinked()). Creating an unlinked table is
> > useful for splitting level 1 and 2 entries into subtrees of PAGE_SIZE
> > PTEs. For example, a level 1 entry can be split into PAGE_SIZE PTEs
> > by first creating a fully populated tree, and then use it to replace
> > the level 1 entry in a single step. This will be used in a subsequent
> > commit for eager huge-page splitting (a dirty-logging optimization).
> >
> > Signed-off-by: Ricardo Koller <ricarkol@xxxxxxxxxx>
> > Reviewed-by: Shaoqin Huang <shahuang@xxxxxxxxxx>
> > ---
> > arch/arm64/include/asm/kvm_pgtable.h | 26 +++++++++++++++
> > arch/arm64/kvm/hyp/pgtable.c | 49 ++++++++++++++++++++++++++++
> > 2 files changed, 75 insertions(+)
> >
>
> With the following nits addressed:
>
> Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>
>
> > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> > index 3f2d43ba2b628..c8e0e7d9303b2 100644
> > --- a/arch/arm64/include/asm/kvm_pgtable.h
> > +++ b/arch/arm64/include/asm/kvm_pgtable.h
> > @@ -458,6 +458,32 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
> > */
> > void kvm_pgtable_stage2_free_unlinked(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level);
> > +/**
> > + * kvm_pgtable_stage2_create_unlinked() - Create an unlinked stage-2 paging structure.
> > + * @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*().
> > + * @phys: Physical address of the memory to map.
> > + * @level: Starting level of the stage-2 paging structure to be created.
> > + * @prot: Permissions and attributes for the mapping.
> > + * @mc: Cache of pre-allocated and zeroed memory from which to allocate
> ^^^^^^^^
> Alignment.
This seems to be due to the "+ ". It looks like this without it:
* kvm_pgtable_stage2_create_unlinked() - Create an unlinked stage-2 paging structure.
* @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*().
* @phys: Physical address of the memory to map.
* @level: Starting level of the stage-2 paging structure to be created.
* @prot: Permissions and attributes for the mapping.
* @mc: Cache of pre-allocated and zeroed memory from which to allocate
* page-table pages.
>
> > + * page-table pages.
> > + * @force_pte: Force mappings to PAGE_SIZE granularity.
> > + *
> > + * Returns an unlinked page-table tree. This new page-table tree is
> > + * not reachable (i.e., it is unlinked) from the root pgd and it's
> > + * therefore unreachableby the hardware page-table walker. No TLB
> > + * invalidation or CMOs are performed.
> > + *
> > + * If device attributes are not explicitly requested in @prot, then the
> > + * mapping will be normal, cacheable.
> > + *
> > + * Return: The fully populated (unlinked) stage-2 paging structure, or
> > + * an ERR_PTR(error) on failure.
> > + */
> > +kvm_pte_t *kvm_pgtable_stage2_create_unlinked(struct kvm_pgtable *pgt,
> > + u64 phys, u32 level,
> > + enum kvm_pgtable_prot prot,
> > + void *mc, bool force_pte);
> > +
> > /**
> > * kvm_pgtable_stage2_map() - Install a mapping in a guest stage-2 page-table.
> > * @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*().
> > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> > index 633679ee3c49a..477d2be67d401 100644
> > --- a/arch/arm64/kvm/hyp/pgtable.c
> > +++ b/arch/arm64/kvm/hyp/pgtable.c
> > @@ -1222,6 +1222,55 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size)
> > return kvm_pgtable_walk(pgt, addr, size, &walker);
> > }
> > +kvm_pte_t *kvm_pgtable_stage2_create_unlinked(struct kvm_pgtable *pgt,
> > + u64 phys, u32 level,
> > + enum kvm_pgtable_prot prot,
> > + void *mc, bool force_pte)
> > +{
> > + struct stage2_map_data map_data = {
> > + .phys = phys,
> > + .mmu = pgt->mmu,
> > + .memcache = mc,
> > + .force_pte = force_pte,
> > + };
> > + struct kvm_pgtable_walker walker = {
> > + .cb = stage2_map_walker,
> > + .flags = KVM_PGTABLE_WALK_LEAF |
> > + KVM_PGTABLE_WALK_SKIP_BBM_TLBI |
> > + KVM_PGTABLE_WALK_SKIP_CMO,
> > + .arg = &map_data,
> > + };
> > + /* .addr (the IPA) is irrelevant for an unlinked table */
> > + struct kvm_pgtable_walk_data data = {
> > + .walker = &walker,
> > + .addr = 0,
> > + .end = kvm_granule_size(level),
> > + };
>
> The comment about '.addr' seems incorrect. The IPA address is still
> used to locate the page table entry, so I think it would be something
> like below:
>
> /* The IPA address (.addr) is relative to zero */
>
Extended it to say this:
* The IPA address (.addr) is relative to zero. The goal is to
* map "kvm_granule_size(level) - 0" worth of pages.
> > + struct kvm_pgtable_mm_ops *mm_ops = pgt->mm_ops;
> > + kvm_pte_t *pgtable;
> > + int ret;
> > +
> > + if (!IS_ALIGNED(phys, kvm_granule_size(level)))
> > + return ERR_PTR(-EINVAL);
> > +
> > + ret = stage2_set_prot_attr(pgt, prot, &map_data.attr);
> > + if (ret)
> > + return ERR_PTR(ret);
> > +
> > + pgtable = mm_ops->zalloc_page(mc);
> > + if (!pgtable)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + ret = __kvm_pgtable_walk(&data, mm_ops, (kvm_pteref_t)pgtable,
> > + level + 1);
> > + if (ret) {
> > + kvm_pgtable_stage2_free_unlinked(mm_ops, pgtable, level);
> > + mm_ops->put_page(pgtable);
> > + return ERR_PTR(ret);
> > + }
> > +
> > + return pgtable;
> > +}
> > int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu,
> > struct kvm_pgtable_mm_ops *mm_ops,
> >
>
> Thanks,
> Gavin
>
