| Message ID | 20210729132818.4091769-9-qperret@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Track shared pages at EL2 in protected mode | expand |
Hi Quentin, On Thu, Jul 29, 2021 at 3:28 PM Quentin Perret <qperret@google.com> wrote: > > We will soon start annotating page-tables with new flags to track shared > pages and such, and we will do so in valid mappings using software bits > in the PTEs, as provided by the architecture. However, it is possible > that we will need to use those flags to annotate invalid mappings as > well in the future, similar to what we do to track page ownership in the > host stage-2. > > In order to facilitate the annotation of invalid mappings with such > flags, it would be preferable to re-use the same bits as for valid > mappings (bits [58-55]), but these are currently used for ownership > encoding. Since we have plenty of bits left to use in invalid > mappings, move the ownership bits further down the PTE to avoid the > conflict. > > Signed-off-by: Quentin Perret <qperret@google.com> > --- > arch/arm64/kvm/hyp/pgtable.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 59a394d82de3..1ee1168ac32d 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -46,7 +46,7 @@ > KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \ > KVM_PTE_LEAF_ATTR_HI_S2_XN) > > -#define KVM_INVALID_PTE_OWNER_MASK GENMASK(63, 56) > +#define KVM_INVALID_PTE_OWNER_MASK GENMASK(9, 2) > #define KVM_MAX_OWNER_ID 1 This change makes sense so that the same bits can be used to track sharing. Reviewed-by: Fuad Tabba <tabba@google.com> Thanks, /fuad > > struct kvm_pgtable_walk_data { > -- > 2.32.0.432.gabb21c7263-goog >
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 59a394d82de3..1ee1168ac32d 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -46,7 +46,7 @@ KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \ KVM_PTE_LEAF_ATTR_HI_S2_XN) -#define KVM_INVALID_PTE_OWNER_MASK GENMASK(63, 56) +#define KVM_INVALID_PTE_OWNER_MASK GENMASK(9, 2) #define KVM_MAX_OWNER_ID 1 struct kvm_pgtable_walk_data {
We will soon start annotating page-tables with new flags to track shared pages and such, and we will do so in valid mappings using software bits in the PTEs, as provided by the architecture. However, it is possible that we will need to use those flags to annotate invalid mappings as well in the future, similar to what we do to track page ownership in the host stage-2. In order to facilitate the annotation of invalid mappings with such flags, it would be preferable to re-use the same bits as for valid mappings (bits [58-55]), but these are currently used for ownership encoding. Since we have plenty of bits left to use in invalid mappings, move the ownership bits further down the PTE to avoid the conflict. Signed-off-by: Quentin Perret <qperret@google.com> --- arch/arm64/kvm/hyp/pgtable.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)