Re: [PATCH v1 05/12] KVM: arm64: Maintain page-table format info in struct kvm_pgtable

[Oliver Upton]

Hi Ryan,

On Tue, Dec 06, 2022 at 01:59:23PM +, Ryan Roberts wrote:
> As the next step on the journey to supporting FEAT_LPA2 in KVM, add a
> flag to struct kvm_pgtable, which functions can then use to select the
> approprate behavior for either the `classic` or `lpa2` page-table
> formats. For now, all page-tables remain in the `classic` format.
> 
> No functional changes are intended.
> 
> Signed-off-by: Ryan Roberts 
> ---
>  arch/arm64/include/asm/kvm_pgtable.h | 2 ++
>  arch/arm64/kvm/hyp/pgtable.c | 2 ++
>  arch/arm64/kvm/mmu.c | 1 +
>  3 files changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_pgtable.h 
> b/arch/arm64/include/asm/kvm_pgtable.h
> index 2247ed74871a..744e224d964b 100644
> --- a/arch/arm64/include/asm/kvm_pgtable.h
> +++ b/arch/arm64/include/asm/kvm_pgtable.h
> @@ -157,6 +157,7 @@ typedef bool (*kvm_pgtable_force_pte_cb_t)(u64 addr, u64 
> end,
>   * @start_level: Level at which the page-table walk starts.
>   * @pgd: Pointer to the first top-level entry of the page-table.
>   * @mm_ops:  Memory management callbacks.
> + * @lpa2_ena:Format used for page-table; false->classic, 
> true->lpa2.

I'd prefer that we describe the paging structure purely in terms of
input and output address. If you add the latter it should be possible to
decide if LPA2 is actually in use.

(i.e. PAGE_SIZE != SZ_64K && pgt->oa_bits > 48)

--
Thanks,
Oliver
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[PATCH v1 05/12] KVM: arm64: Maintain page-table format info in struct kvm_pgtable

[Ryan Roberts]

As the next step on the journey to supporting FEAT_LPA2 in KVM, add a
flag to struct kvm_pgtable, which functions can then use to select the
approprate behavior for either the `classic` or `lpa2` page-table
formats. For now, all page-tables remain in the `classic` format.

No functional changes are intended.

Signed-off-by: Ryan Roberts 
---
 arch/arm64/include/asm/kvm_pgtable.h | 2 ++
 arch/arm64/kvm/hyp/pgtable.c | 2 ++
 arch/arm64/kvm/mmu.c | 1 +
 3 files changed, 5 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h 
b/arch/arm64/include/asm/kvm_pgtable.h
index 2247ed74871a..744e224d964b 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -157,6 +157,7 @@ typedef bool (*kvm_pgtable_force_pte_cb_t)(u64 addr, u64 
end,
  * @start_level:   Level at which the page-table walk starts.
  * @pgd:   Pointer to the first top-level entry of the page-table.
  * @mm_ops:Memory management callbacks.
+ * @lpa2_ena:  Format used for page-table; false->classic, true->lpa2.
  * @mmu:   Stage-2 KVM MMU struct. Unused for stage-1 page-tables.
  * @flags: Stage-2 page-table flags.
  * @force_pte_cb:  Function that returns true if page level mappings must
@@ -167,6 +168,7 @@ struct kvm_pgtable {
u32 start_level;
kvm_pte_t   *pgd;
struct kvm_pgtable_mm_ops   *mm_ops;
+   boollpa2_ena;
 
/* Stage-2 only */
struct kvm_s2_mmu   *mmu;
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 221e0dafb149..c7799cd50af8 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -530,6 +530,7 @@ int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 
va_bits,
pgt->ia_bits= va_bits;
pgt->start_level= KVM_PGTABLE_MAX_LEVELS - levels;
pgt->mm_ops = mm_ops;
+   pgt->lpa2_ena   = false;
pgt->mmu= NULL;
pgt->force_pte_cb   = NULL;
 
@@ -1190,6 +1191,7 @@ int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, 
struct kvm_s2_mmu *mmu,
pgt->ia_bits= ia_bits;
pgt->start_level= start_level;
pgt->mm_ops = mm_ops;
+   pgt->lpa2_ena   = false;
pgt->mmu= mmu;
pgt->flags  = flags;
pgt->force_pte_cb   = force_pte_cb;
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 1ef0704420d9..e3fe3e194fd1 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -645,6 +645,7 @@ static int get_user_mapping_size(struct kvm *kvm, u64 addr)
.start_level= (KVM_PGTABLE_MAX_LEVELS -
   CONFIG_PGTABLE_LEVELS),
.mm_ops = &kvm_user_mm_ops,
+   .lpa2_ena   = lpa2_is_enabled(),
};
kvm_pte_t pte = 0;  /* Keep GCC quiet... */
u32 level = ~0;
-- 
2.25.1

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