Re: [PATCH 8/8] arm64: KVM: Implement 4 levels of translation tables for HYP and stage2

[Marc Zyngier]

On 14/04/14 08:41, Jungseok Lee wrote:
> This patch adds 4 levels of translation tables implementation for both
> HYP and stage2. A combination of 4KB + 4 levels host and 4KB + 4 levels
> guest can run on ARMv8 architecture as introducing this feature.
> 
> Signed-off-by: Jungseok Lee <jays.lee@xxxxxxxxxxx>
> Reviewed-by: Sungjinn Chung <sungjinn.chung@xxxxxxxxxxx>
> ---
>  arch/arm/kvm/mmu.c               |   96 +++++++++++++++++++++++++++++++++-----
>  arch/arm64/include/asm/kvm_arm.h |   20 ++++++++
>  arch/arm64/include/asm/kvm_mmu.h |    1 +
>  3 files changed, 106 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index e0d4f24..6cf89ad 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -388,13 +388,46 @@ static int create_hyp_pmd_mappings(pud_t *pud, unsigned long start,
>  	return 0;
>  }
>  
> +static int create_hyp_pud_mappings(pgd_t *pgd, unsigned long start,
> +				   unsigned long end, unsigned long pfn,
> +				   pgprot_t prot)
> +{
> +	pud_t *pud;
> +	pmd_t *pmd;
> +	unsigned long addr, next;
> +
> +	addr = start;
> +	do {
> +		pud = pud_offset(pgd, addr);
> +
> +		if (pud_none_or_clear_bad(pud)) {
> +			pmd = pmd_alloc_one(NULL, addr);
> +			if (!pmd) {
> +				kvm_err("Cannot allocate Hyp pmd\n");
> +				return -ENOMEM;
> +			}
> +			pud_populate(NULL, pud, pmd);
> +			get_page(virt_to_page(pud));
> +			kvm_flush_dcache_to_poc(pud, sizeof(*pud));
> +		}
> +
> +		next = pud_addr_end(addr, end);
> +
> +		create_hyp_pmd_mappings(pud, addr, next, pfn, prot);
> +		pfn += (next - addr) >> PAGE_SHIFT;
> +	} while (addr = next, addr != end);
> +
> +	return 0;
> +}
> +
>  static int __create_hyp_mappings(pgd_t *pgdp,
>  				 unsigned long start, unsigned long end,
>  				 unsigned long pfn, pgprot_t prot)
>  {
>  	pgd_t *pgd;
> +#ifdef CONFIG_ARM64_4_LEVELS
>  	pud_t *pud;
> -	pmd_t *pmd;
> +#endif
>  	unsigned long addr, next;
>  	int err = 0;
>  
> @@ -403,22 +436,25 @@ static int __create_hyp_mappings(pgd_t *pgdp,
>  	end = PAGE_ALIGN(end);
>  	do {
>  		pgd = pgdp + pgd_index(addr);
> -		pud = pud_offset(pgd, addr);
>  
> -		if (pud_none_or_clear_bad(pud)) {
> -			pmd = pmd_alloc_one(NULL, addr);
> -			if (!pmd) {
> -				kvm_err("Cannot allocate Hyp pmd\n");
> +#ifdef CONFIG_ARM64_4_LEVELS
> +		if (pgd_none(*pgd)) {
> +			pud = pud_alloc_one(NULL, addr);
> +			if (!pud) {
> +				kvm_err("Cannot allocate Hyp pud\n");
>  				err = -ENOMEM;
>  				goto out;
>  			}
> -			pud_populate(NULL, pud, pmd);
> -			get_page(virt_to_page(pud));
> -			kvm_flush_dcache_to_poc(pud, sizeof(*pud));
> +			pgd_populate(NULL, pgd, pud);
> +			get_page(virt_to_page(pgd));
> +			kvm_flush_dcache_to_poc(pgd, sizeof(*pgd));
>  		}
> +#endif

Why do you need all these #ifdefs? The page table code should be able to
cope with all the variations of presence/absence of pud/pmd (see how
there is no code difference between 4kB (3 levels) and 64kB (2 levels)).

>  		next = pgd_addr_end(addr, end);
> -		err = create_hyp_pmd_mappings(pud, addr, next, pfn, prot);
> +
> +		err = create_hyp_pud_mappings(pgd, addr, next, pfn, prot);
> +
>  		if (err)
>  			goto out;
>  		pfn += (next - addr) >> PAGE_SHIFT;
> @@ -563,6 +599,26 @@ void kvm_free_stage2_pgd(struct kvm *kvm)
>  	kvm->arch.pgd = NULL;
>  }
>  
> +#ifdef CONFIG_ARM64_4_LEVELS
> +static pud_t *stage2_get_pud(struct kvm *kvm, struct kvm_mmu_memory_cache
> +			     *cache, phys_addr_t addr)
> +{
> +	pgd_t *pgd;
> +	pud_t *pud;
> +
> +	pgd = kvm->arch.pgd + pgd_index(addr);
> +	if (pgd_none(*pgd)) {
> +		if (!cache)
> +			return NULL;
> +		pud = mmu_memory_cache_alloc(cache);
> +		pgd_populate(NULL, pgd, pud);
> +		get_page(virt_to_page(pgd));
> +	}
> +
> +	return pud_offset(pgd, addr);
> +}
> +#endif

Same here.

>  static pmd_t *stage2_get_pmd(struct kvm *kvm, struct kvm_mmu_memory_cache
>  			     *cache, phys_addr_t addr)
>  {
> @@ -617,6 +673,24 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
>  	pmd_t *pmd;
>  	pte_t *pte, old_pte;
>  
> +#ifdef CONFIG_ARM64_4_LEVELS
> +	pud_t *pud;
> +
> +	/* Create stage-2 page table mapping - Level 0 */
> +	pud = stage2_get_pud(kvm, cache, addr);
> +	if (!pud)
> +		return 0;
> +
> +	if (pud_none(*pud)) {
> +		if (!cache)
> +			return 0;
> +		pmd = mmu_memory_cache_alloc(cache);
> +		kvm_clean_pmd(pmd);
> +		pud_populate(NULL, pud, pmd);
> +		get_page(virt_to_page(pud));
> +	}
> +#endif
> +

And here.

>  	/* Create stage-2 page table mapping - Level 1 */
>  	pmd = stage2_get_pmd(kvm, cache, addr);
>  	if (!pmd) {
> @@ -675,7 +749,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>  	for (addr = guest_ipa; addr < end; addr += PAGE_SIZE) {
>  		pte_t pte = pfn_pte(pfn, PAGE_S2_DEVICE);
>  
> -		ret = mmu_topup_memory_cache(&cache, 2, 2);
> +		ret = mmu_topup_memory_cache(&cache, 3, 3);

It would be good to make this depend of the number of levels we're
actually using (2, 3 or 4).

>  		if (ret)
>  			goto out;
>  		spin_lock(&kvm->mmu_lock);
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 3d69030..295eda6 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -117,9 +117,11 @@
>  #define VTCR_EL2_IRGN0_MASK	(3 << 8)
>  #define VTCR_EL2_IRGN0_WBWA	(1 << 8)
>  #define VTCR_EL2_SL0_MASK	(3 << 6)
> +#define VTCR_EL2_SL0_LVL0	(2 << 6)
>  #define VTCR_EL2_SL0_LVL1	(1 << 6)
>  #define VTCR_EL2_T0SZ_MASK	0x3f
>  #define VTCR_EL2_T0SZ_40B	24
> +#define VTCR_EL2_T0SZ_48B	16
>  
>  #ifdef CONFIG_ARM64_64K_PAGES
>  /*
> @@ -134,6 +136,7 @@
>  				 VTCR_EL2_SL0_LVL1 | VTCR_EL2_T0SZ_40B)
>  #define VTTBR_X		(38 - VTCR_EL2_T0SZ_40B)
>  #else
> +#ifndef CONFIG_ARM64_4_LEVELS
>  /*
>   * Stage2 translation configuration:
>   * 40bits output (PS = 2)
> @@ -145,10 +148,27 @@
>  				 VTCR_EL2_ORGN0_WBWA | VTCR_EL2_IRGN0_WBWA | \
>  				 VTCR_EL2_SL0_LVL1 | VTCR_EL2_T0SZ_40B)
>  #define VTTBR_X		(37 - VTCR_EL2_T0SZ_40B)
> +#else
> +/*
> + * Stage2 translation configuration:
> + * 40bits output (PS = 2)
> + * 48bits input  (T0SZ = 16)
> + * 4kB pages (TG0 = 0)
> + * 4 level page tables (SL = 2)
> + */
> +#define VTCR_EL2_FLAGS		(VTCR_EL2_TG0_4K | VTCR_EL2_SH0_INNER | \
> +				 VTCR_EL2_ORGN0_WBWA | VTCR_EL2_IRGN0_WBWA | \
> +				 VTCR_EL2_SL0_LVL0 | VTCR_EL2_T0SZ_48B)
> +#define VTTBR_X		(29 - VTCR_EL2_T0SZ_48B)
> +#endif
>  #endif
>  
>  #define VTTBR_BADDR_SHIFT (VTTBR_X - 1)
> +#ifndef CONFIG_ARM64_4_LEVELS
>  #define VTTBR_BADDR_MASK  (((1LLU << (40 - VTTBR_X)) - 1) << VTTBR_BADDR_SHIFT)
> +#else
> +#define VTTBR_BADDR_MASK  (((1LLU << (48 - VTTBR_X)) - 1) << VTTBR_BADDR_SHIFT)
> +#endif
>  #define VTTBR_VMID_SHIFT  (48LLU)
>  #define VTTBR_VMID_MASK	  (0xffLLU << VTTBR_VMID_SHIFT)
>  
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 7d29847..ec76cf3 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -107,6 +107,7 @@ static inline bool kvm_is_write_fault(unsigned long esr)
>  }
>  
>  static inline void kvm_clean_pgd(pgd_t *pgd) {}
> +static inline void kvm_clean_pmd(pud_t *pud) {}
>  static inline void kvm_clean_pmd_entry(pmd_t *pmd) {}
>  static inline void kvm_clean_pte(pte_t *pte) {}
>  static inline void kvm_clean_pte_entry(pte_t *pte) {}
> 

You'll need to add the 32bit ARM equivalent once you've removed the #ifdefs.

	M.
-- 
Jazz is not dead. It just smells funny...
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