On Mon, Nov 14, 2022 at 08:11:27PM +0000, Oliver Upton wrote: > A subsequent change to the page table walkers adds RCU protection for > walking stage-2 page tables. KVM uses a global lock to serialize hyp > stage-1 walks, meaning RCU protection is quite meaningless for > protecting hyp stage-1 walkers. > > Add a new helper, kvm_pgtable_hyp_walk(), for use when walking hyp > stage-1 tables. Call directly into __kvm_pgtable_walk() as table > concatenation is not a supported feature at stage-1. > > No functional change intended. > > Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx> > --- > arch/arm64/include/asm/kvm_pgtable.h | 24 ++++++++++++++++++++++++ > arch/arm64/kvm/hyp/nvhe/setup.c | 2 +- > arch/arm64/kvm/hyp/pgtable.c | 18 +++++++++++++++--- > 3 files changed, 40 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > index a874ce0ce7b5..43b2f1882e11 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -596,6 +596,30 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size); > int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size, > struct kvm_pgtable_walker *walker); > > +/** > + * kvm_pgtable_hyp_walk() - Walk a hyp stage-1 page-table. > + * @pgt: Page-table structure initialized by kvm_pgtable_hyp_init(). > + * @addr: Input address for the start of the walk. > + * @size: Size of the range to walk. > + * @walker: Walker callback description. > + * > + * The offset of @addr within a page is ignored and @size is rounded-up to > + * the next page boundary. > + * > + * The walker will walk the page-table entries corresponding to the input > + * address range specified, visiting entries according to the walker flags. > + * Invalid entries are treated as leaf entries. Leaf entries are reloaded > + * after invoking the walker callback, allowing the walker to descend into > + * a newly installed table. > + * > + * Returning a negative error code from the walker callback function will > + * terminate the walk immediately with the same error code. > + * > + * Return: 0 on success, negative error code on failure. > + */ > +int kvm_pgtable_hyp_walk(struct kvm_pgtable *pgt, u64 addr, u64 size, > + struct kvm_pgtable_walker *walker); Hmm, this feels like slightly the wrong abstraction to me -- there's nothing hyp-specific about the problem being solved, it's just that the only user is for hyp walks. Could we instead rework 'struct kvm_pgtable' slightly so that the existing 'flags' field is no-longer stage-2 specific and includes a KVM_PGTABLE_LOCKED flag which could be set by kvm_pgtable_hyp_init()? That way the top-level API remains unchanged and the existing callers will continue to work. Cheers, Will
