Hi Quentin,
On Mon, Jul 19, 2021 at 11:47 AM Quentin Perret <qperret@xxxxxxxxxx> wrote:
>
> The current hypervisor stage-1 mapping code doesn't allow changing an
> existing valid mapping. Relax this condition by allowing changes that
> only target ignored bits, as that will soon be needed to annotate shared
> pages.
>
> Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx>
> ---
> arch/arm64/kvm/hyp/pgtable.c | 18 ++++++++++++++++--
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index a0ac8c2bc174..34cf67997a82 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -362,6 +362,17 @@ static int hyp_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep)
> return 0;
> }
>
> +static bool hyp_pte_needs_update(kvm_pte_t old, kvm_pte_t new)
> +{
> + if (old == new)
> + return false;
> +
> + if (!kvm_pte_valid(old))
> + return true;
> +
> + return !WARN_ON((old ^ new) & ~KVM_PTE_LEAF_ATTR_IGNORED);
Wouldn't this return false if both ignored and non-ignored bits were
different, or is that not possible (judging by the WARN_ON)? If it is,
then it would need an update, wouldn't it?
Thanks,
/fuad
> +}
> +
> static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level,
> kvm_pte_t *ptep, struct hyp_map_data *data)
> {
> @@ -371,9 +382,12 @@ static bool hyp_map_walker_try_leaf(u64 addr, u64 end, u32 level,
> if (!kvm_block_mapping_supported(addr, end, phys, level))
> return false;
>
> - /* Tolerate KVM recreating the exact same mapping */
> + /*
> + * Tolerate KVM recreating the exact same mapping, or changing ignored
> + * bits.
> + */
> new = kvm_init_valid_leaf_pte(phys, data->attr, level);
> - if (old != new && !WARN_ON(kvm_pte_valid(old)))
> + if (hyp_pte_needs_update(old, new))
> smp_store_release(ptep, new);
>
> data->phys += granule;
> --
> 2.32.0.402.g57bb445576-goog
>
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
