On Wed, Feb 15, 2023 at 6:56 PM Shaoqin Huang <shahuang@xxxxxxxxxx> wrote:
>
> Hi Ricardo,
>
> On 2/16/23 01:40, Ricardo Koller wrote:
> > Add two flags to kvm_pgtable_visit_ctx, KVM_PGTABLE_WALK_SKIP_BBM and
> > KVM_PGTABLE_WALK_SKIP_CMO, to indicate that the walk should not
> > perform break-before-make (BBM) nor cache maintenance operations
> > (CMO). This will by a future commit to create unlinked tables not
> > accessible to the HW page-table walker. This is safe as these removed
> > tables are not visible to the HW page-table walker.
> >
> > Signed-off-by: Ricardo Koller <ricarkol@xxxxxxxxxx>
> > ---
> > arch/arm64/include/asm/kvm_pgtable.h | 18 ++++++++++++++++++
> > arch/arm64/kvm/hyp/pgtable.c | 27 ++++++++++++++++-----------
> > 2 files changed, 34 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> > index 63f81b27a4e3..3339192a97a9 100644
> > --- a/arch/arm64/include/asm/kvm_pgtable.h
> > +++ b/arch/arm64/include/asm/kvm_pgtable.h
> > @@ -188,12 +188,20 @@ typedef bool (*kvm_pgtable_force_pte_cb_t)(u64 addr, u64 end,
> > * children.
> > * @KVM_PGTABLE_WALK_SHARED: Indicates the page-tables may be shared
> > * with other software walkers.
> > + * @KVM_PGTABLE_WALK_SKIP_BBM: Visit and update table entries
> > + * without Break-before-make
> > + * requirements.
> > + * @KVM_PGTABLE_WALK_SKIP_CMO: Visit and update table entries
> > + * without Cache maintenance
> > + * operations required.
> > */
> > enum kvm_pgtable_walk_flags {
> > KVM_PGTABLE_WALK_LEAF = BIT(0),
> > KVM_PGTABLE_WALK_TABLE_PRE = BIT(1),
> > KVM_PGTABLE_WALK_TABLE_POST = BIT(2),
> > KVM_PGTABLE_WALK_SHARED = BIT(3),
> > + KVM_PGTABLE_WALK_SKIP_BBM = BIT(4),
> > + KVM_PGTABLE_WALK_SKIP_CMO = BIT(4),
>
> The KVM_PGTABLE_WALK_SKIP_BBM and KVM_PGTABLE_WALK_SKIP_CMO use the same
> BIT(4), if I understand correctly, the two flags are used in different
> operation and will never be used at the same time.
>
That was supposed to be a BIT(5):
KVM_PGTABLE_WALK_SKIP_BBM = BIT(4),
KVM_PGTABLE_WALK_SKIP_CMO = BIT(5),
>
> Maybe add some comments to illustrate why the two use the same bit can
> be better.
>
>
> > };
> >
> > struct kvm_pgtable_visit_ctx {
> > @@ -215,6 +223,16 @@ static inline bool kvm_pgtable_walk_shared(const struct kvm_pgtable_visit_ctx *c
> > return ctx->flags & KVM_PGTABLE_WALK_SHARED;
> > }
> >
> > +static inline bool kvm_pgtable_walk_skip_bbm(const struct kvm_pgtable_visit_ctx *ctx)
> > +{
> > + return ctx->flags & KVM_PGTABLE_WALK_SKIP_BBM;
> > +}
> > +
> > +static inline bool kvm_pgtable_walk_skip_cmo(const struct kvm_pgtable_visit_ctx *ctx)
> > +{
> > + return ctx->flags & KVM_PGTABLE_WALK_SKIP_CMO;
> > +}
> > +
> > /**
> > * struct kvm_pgtable_walker - Hook into a page-table walk.
> > * @cb: Callback function to invoke during the walk.
> > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> > index b11cf2c618a6..e093e222daf3 100644
> > --- a/arch/arm64/kvm/hyp/pgtable.c
> > +++ b/arch/arm64/kvm/hyp/pgtable.c
> > @@ -717,14 +717,17 @@ static bool stage2_try_break_pte(const struct kvm_pgtable_visit_ctx *ctx,
> > if (!stage2_try_set_pte(ctx, KVM_INVALID_PTE_LOCKED))
> > return false;
> >
> > - /*
> > - * Perform the appropriate TLB invalidation based on the evicted pte
> > - * value (if any).
> > - */
> > - if (kvm_pte_table(ctx->old, ctx->level))
> > - kvm_call_hyp(__kvm_tlb_flush_vmid, mmu);
> > - else if (kvm_pte_valid(ctx->old))
> > - kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu, ctx->addr, ctx->level);
> > + if (!kvm_pgtable_walk_skip_bbm(ctx)) {
> > + /*
> > + * Perform the appropriate TLB invalidation based on the
> > + * evicted pte value (if any).
> > + */
> > + if (kvm_pte_table(ctx->old, ctx->level))
> > + kvm_call_hyp(__kvm_tlb_flush_vmid, mmu);
> > + else if (kvm_pte_valid(ctx->old))
> > + kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, mmu,
> > + ctx->addr, ctx->level);
> > + }
> >
> > if (stage2_pte_is_counted(ctx->old))
> > mm_ops->put_page(ctx->ptep);
> > @@ -808,11 +811,13 @@ static int stage2_map_walker_try_leaf(const struct kvm_pgtable_visit_ctx *ctx,
> > return -EAGAIN;
> >
> > /* Perform CMOs before installation of the guest stage-2 PTE */
> > - if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
> > + if (!kvm_pgtable_walk_skip_cmo(ctx) && mm_ops->dcache_clean_inval_poc &&
> > + stage2_pte_cacheable(pgt, new))
> > mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
> > - granule);
> > + granule);
> >
> > - if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> > + if (!kvm_pgtable_walk_skip_cmo(ctx) && mm_ops->icache_inval_pou &&
> > + stage2_pte_executable(new))
> > mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
> >
> > stage2_make_pte(ctx, new);
>
> --
> Regards,
> Shaoqin
>
