Re: [PATCH v5 10/18] kvm: arm64: Make stage2 page table layout dynamic

From: Auger Eric
Date: Thu Sep 20 2018 - 10:07:17 EST

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Hi Suzuki,

On 9/17/18 12:41 PM, Suzuki K Poulose wrote:
> Switch to dynamic stage2 page table layout based on the given
> VM. So far we had a common stage2 table layout determined at
> compile time. Make decision based on the VM instance depending
> on the IPA limit for the VM. Adds helpers to compute the stage2
> parameters based on the guest's IPA and uses them to make the decisions.
>
> The IPA limit is still fixed to 40bits and the build time check
> to ensure the stage2 doesn't exceed the host kernels page table
> levels is retained. Also make sure that the host has pud/pmd helpers
> are used only when they are available at host.
needs some rewording.
>
> Cc: Christoffer Dall <cdall@xxxxxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> arch/arm64/include/asm/stage2_pgtable.h | 84 +++++++++++++++----------
> 1 file changed, 52 insertions(+), 32 deletions(-)
>
> diff --git a/arch/arm64/include/asm/stage2_pgtable.h b/arch/arm64/include/asm/stage2_pgtable.h
> index 384f9e982cba..e5acda8e2e31 100644
> --- a/arch/arm64/include/asm/stage2_pgtable.h
> +++ b/arch/arm64/include/asm/stage2_pgtable.h
> @@ -22,6 +22,13 @@
> #include <linux/hugetlb.h>
> #include <asm/pgtable.h>
>
> +/*
> + * PGDIR_SHIFT determines the size a top-level page table entry can map
strictly speaking it is the index of the start level, right? size of the
top-level page table entry is 1 << PGDIR_SHIFT
> + * and depends on the number of levels in the page table. Compute the
> + * PGDIR_SHIFT for a given number of levels.
> + */
> +#define pt_levels_pgdir_shift(n) ARM64_HW_PGTABLE_LEVEL_SHIFT(4 - (n))
why not using lvls instead of n as below?

Besides
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>

Thanks

Eric
> +
> /*
> * The hardware supports concatenation of up to 16 tables at stage2 entry level
> * and we use the feature whenever possible.
> @@ -30,11 +37,13 @@
> * On arm64, the smallest PAGE_SIZE supported is 4k, which means
> * (PAGE_SHIFT - 3) > 4 holds for all page sizes.
> * This implies, the total number of page table levels at stage2 expected
> - * by the hardware is actually the number of levels required for (KVM_PHYS_SHIFT - 4)
> + * by the hardware is actually the number of levels required for (IPA_SHIFT - 4)
> * in normal translations(e.g, stage1), since we cannot have another level in
> - * the range (KVM_PHYS_SHIFT, KVM_PHYS_SHIFT - 4).
> + * the range (IPA_SHIFT, IPA_SHIFT - 4).
> */
> -#define STAGE2_PGTABLE_LEVELS ARM64_HW_PGTABLE_LEVELS(KVM_PHYS_SHIFT - 4)
> +#define stage2_pgtable_levels(ipa) ARM64_HW_PGTABLE_LEVELS((ipa) - 4)
> +#define STAGE2_PGTABLE_LEVELS stage2_pgtable_levels(KVM_PHYS_SHIFT)
> +#define kvm_stage2_levels(kvm) stage2_pgtable_levels(kvm_phys_shift(kvm))
>
> /*
> * With all the supported VA_BITs and 40bit guest IPA, the following condition
> @@ -54,33 +63,42 @@
> #error "Unsupported combination of guest IPA and host VA_BITS."
> #endif
>
> -/* S2_PGDIR_SHIFT is the size mapped by top-level stage2 entry */
> -#define S2_PGDIR_SHIFT ARM64_HW_PGTABLE_LEVEL_SHIFT(4 - STAGE2_PGTABLE_LEVELS)
> -#define S2_PGDIR_SIZE (1UL << S2_PGDIR_SHIFT)
> -#define S2_PGDIR_MASK (~(S2_PGDIR_SIZE - 1))
> +
> +/* stage2_pgdir_shift() is the size mapped by top-level stage2 entry for the VM */
> +#define stage2_pgdir_shift(kvm) pt_levels_pgdir_shift(kvm_stage2_levels(kvm))
> +#define stage2_pgdir_size(kvm) (1ULL << stage2_pgdir_shift(kvm))
> +#define stage2_pgdir_mask(kvm) ~(stage2_pgdir_size(kvm) - 1)
>
> /*
> * The number of PTRS across all concatenated stage2 tables given by the
> * number of bits resolved at the initial level.
> */
> -#define PTRS_PER_S2_PGD (1 << (KVM_PHYS_SHIFT - S2_PGDIR_SHIFT))
> +#define __s2_pgd_ptrs(ipa, lvls) (1 << ((ipa) - pt_levels_pgdir_shift((lvls))))
> +#define __s2_pgd_size(ipa, lvls) (__s2_pgd_ptrs((ipa), (lvls)) * sizeof(pgd_t))
> +
> +#define stage2_pgd_ptrs(kvm) __s2_pgd_ptrs(kvm_phys_shift(kvm), kvm_stage2_levels(kvm))
> +#define stage2_pgd_size(kvm) __s2_pgd_size(kvm_phys_shift(kvm), kvm_stage2_levels(kvm))
>
> /*
> * kvm_mmmu_cache_min_pages() is the number of pages required to install
> * a stage-2 translation. We pre-allocate the entry level page table at
> * the VM creation.
> */
> -#define kvm_mmu_cache_min_pages(kvm) (STAGE2_PGTABLE_LEVELS - 1)
> +#define kvm_mmu_cache_min_pages(kvm) (kvm_stage2_levels(kvm) - 1)
>
> /* Stage2 PUD definitions when the level is present */
> -#define STAGE2_PGTABLE_HAS_PUD (STAGE2_PGTABLE_LEVELS > 3)
> +static inline bool kvm_stage2_has_pud(struct kvm *kvm)
> +{
> + return (CONFIG_PGTABLE_LEVELS > 3) && (kvm_stage2_levels(kvm) > 3);
> +}
> +
> #define S2_PUD_SHIFT ARM64_HW_PGTABLE_LEVEL_SHIFT(1)
> #define S2_PUD_SIZE (1UL << S2_PUD_SHIFT)
> #define S2_PUD_MASK (~(S2_PUD_SIZE - 1))
>
> static inline bool stage2_pgd_none(struct kvm *kvm, pgd_t pgd)
> {
> - if (STAGE2_PGTABLE_HAS_PUD)
> + if (kvm_stage2_has_pud(kvm))
> return pgd_none(pgd);
> else
> return 0;
> @@ -88,13 +106,13 @@ static inline bool stage2_pgd_none(struct kvm *kvm, pgd_t pgd)
>
> static inline void stage2_pgd_clear(struct kvm *kvm, pgd_t *pgdp)
> {
> - if (STAGE2_PGTABLE_HAS_PUD)
> + if (kvm_stage2_has_pud(kvm))
> pgd_clear(pgdp);
> }
>
> static inline bool stage2_pgd_present(struct kvm *kvm, pgd_t pgd)
> {
> - if (STAGE2_PGTABLE_HAS_PUD)
> + if (kvm_stage2_has_pud(kvm))
> return pgd_present(pgd);
> else
> return 1;
> @@ -102,14 +120,14 @@ static inline bool stage2_pgd_present(struct kvm *kvm, pgd_t pgd)
>
> static inline void stage2_pgd_populate(struct kvm *kvm, pgd_t *pgd, pud_t *pud)
> {
> - if (STAGE2_PGTABLE_HAS_PUD)
> + if (kvm_stage2_has_pud(kvm))
> pgd_populate(NULL, pgd, pud);
> }
>
> static inline pud_t *stage2_pud_offset(struct kvm *kvm,
> pgd_t *pgd, unsigned long address)
> {
> - if (STAGE2_PGTABLE_HAS_PUD)
> + if (kvm_stage2_has_pud(kvm))
> return pud_offset(pgd, address);
> else
> return (pud_t *)pgd;
> @@ -117,13 +135,13 @@ static inline pud_t *stage2_pud_offset(struct kvm *kvm,
>
> static inline void stage2_pud_free(struct kvm *kvm, pud_t *pud)
> {
> - if (STAGE2_PGTABLE_HAS_PUD)
> + if (kvm_stage2_has_pud(kvm))
> pud_free(NULL, pud);
> }
>
> static inline bool stage2_pud_table_empty(struct kvm *kvm, pud_t *pudp)
> {
> - if (STAGE2_PGTABLE_HAS_PUD)
> + if (kvm_stage2_has_pud(kvm))
> return kvm_page_empty(pudp);
> else
> return false;
> @@ -132,7 +150,7 @@ static inline bool stage2_pud_table_empty(struct kvm *kvm, pud_t *pudp)
> static inline phys_addr_t
> stage2_pud_addr_end(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
> {
> - if (STAGE2_PGTABLE_HAS_PUD) {
> + if (kvm_stage2_has_pud(kvm)) {
> phys_addr_t boundary = (addr + S2_PUD_SIZE) & S2_PUD_MASK;
>
> return (boundary - 1 < end - 1) ? boundary : end;
> @@ -142,14 +160,18 @@ stage2_pud_addr_end(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
> }
>
> /* Stage2 PMD definitions when the level is present */
> -#define STAGE2_PGTABLE_HAS_PMD (STAGE2_PGTABLE_LEVELS > 2)
> +static inline bool kvm_stage2_has_pmd(struct kvm *kvm)
> +{
> + return (CONFIG_PGTABLE_LEVELS > 2) && (kvm_stage2_levels(kvm) > 2);
> +}
> +
> #define S2_PMD_SHIFT ARM64_HW_PGTABLE_LEVEL_SHIFT(2)
> #define S2_PMD_SIZE (1UL << S2_PMD_SHIFT)
> #define S2_PMD_MASK (~(S2_PMD_SIZE - 1))
>
> static inline bool stage2_pud_none(struct kvm *kvm, pud_t pud)
> {
> - if (STAGE2_PGTABLE_HAS_PMD)
> + if (kvm_stage2_has_pmd(kvm))
> return pud_none(pud);
> else
> return 0;
> @@ -157,13 +179,13 @@ static inline bool stage2_pud_none(struct kvm *kvm, pud_t pud)
>
> static inline void stage2_pud_clear(struct kvm *kvm, pud_t *pud)
> {
> - if (STAGE2_PGTABLE_HAS_PMD)
> + if (kvm_stage2_has_pmd(kvm))
> pud_clear(pud);
> }
>
> static inline bool stage2_pud_present(struct kvm *kvm, pud_t pud)
> {
> - if (STAGE2_PGTABLE_HAS_PMD)
> + if (kvm_stage2_has_pmd(kvm))
> return pud_present(pud);
> else
> return 1;
> @@ -171,14 +193,14 @@ static inline bool stage2_pud_present(struct kvm *kvm, pud_t pud)
>
> static inline void stage2_pud_populate(struct kvm *kvm, pud_t *pud, pmd_t *pmd)
> {
> - if (STAGE2_PGTABLE_HAS_PMD)
> + if (kvm_stage2_has_pmd(kvm))
> pud_populate(NULL, pud, pmd);
> }
>
> static inline pmd_t *stage2_pmd_offset(struct kvm *kvm,
> pud_t *pud, unsigned long address)
> {
> - if (STAGE2_PGTABLE_HAS_PMD)
> + if (kvm_stage2_has_pmd(kvm))
> return pmd_offset(pud, address);
> else
> return (pmd_t *)pud;
> @@ -186,13 +208,13 @@ static inline pmd_t *stage2_pmd_offset(struct kvm *kvm,
>
> static inline void stage2_pmd_free(struct kvm *kvm, pmd_t *pmd)
> {
> - if (STAGE2_PGTABLE_HAS_PMD)
> + if (kvm_stage2_has_pmd(kvm))
> pmd_free(NULL, pmd);
> }
>
> static inline bool stage2_pud_huge(struct kvm *kvm, pud_t pud)
> {
> - if (STAGE2_PGTABLE_HAS_PMD)
> + if (kvm_stage2_has_pmd(kvm))
> return pud_huge(pud);
> else
> return 0;
> @@ -200,7 +222,7 @@ static inline bool stage2_pud_huge(struct kvm *kvm, pud_t pud)
>
> static inline bool stage2_pmd_table_empty(struct kvm *kvm, pmd_t *pmdp)
> {
> - if (STAGE2_PGTABLE_HAS_PMD)
> + if (kvm_stage2_has_pmd(kvm))
> return kvm_page_empty(pmdp);
> else
> return 0;
> @@ -209,7 +231,7 @@ static inline bool stage2_pmd_table_empty(struct kvm *kvm, pmd_t *pmdp)
> static inline phys_addr_t
> stage2_pmd_addr_end(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
> {
> - if (STAGE2_PGTABLE_HAS_PMD) {
> + if (kvm_stage2_has_pmd(kvm)) {
> phys_addr_t boundary = (addr + S2_PMD_SIZE) & S2_PMD_MASK;
>
> return (boundary - 1 < end - 1) ? boundary : end;
> @@ -223,17 +245,15 @@ static inline bool stage2_pte_table_empty(struct kvm *kvm, pte_t *ptep)
> return kvm_page_empty(ptep);
> }
>
> -#define stage2_pgd_size(kvm) (PTRS_PER_S2_PGD * sizeof(pgd_t))
> -
> static inline unsigned long stage2_pgd_index(struct kvm *kvm, phys_addr_t addr)
> {
> - return (((addr) >> S2_PGDIR_SHIFT) & (PTRS_PER_S2_PGD - 1));
> + return (((addr) >> stage2_pgdir_shift(kvm)) & (stage2_pgd_ptrs(kvm) - 1));
> }
>
> static inline phys_addr_t
> stage2_pgd_addr_end(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
> {
> - phys_addr_t boundary = (addr + S2_PGDIR_SIZE) & S2_PGDIR_MASK;
> + phys_addr_t boundary = (addr + stage2_pgdir_size(kvm)) & stage2_pgdir_mask(kvm);
>
> return (boundary - 1 < end - 1) ? boundary : end;
> }
>

Next message: Auger Eric: "Re: [PATCH v5 08/18] kvm: arm/arm64: Prepare for VM specific stage2 translations"
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In reply to: Suzuki K Poulose: "[PATCH v5 10/18] kvm: arm64: Make stage2 page table layout dynamic"
Next in thread: Suzuki K Poulose: "[PATCH v5 11/18] kvm: arm64: Dynamic configuration of VTTBR mask"
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