Subject: [PATCH v9 2/4] arm: ARMv7 dirty page logging inital mem region write protect (w/no huge PUD support)

From: [email-masked] (Christoffer Dall)
Date: Mon, 11 Aug 2014 21:12:57 +0200

Remove the parenthesis from the subject line.

On Thu, Jul 24, 2014 at 05:56:06PM -0700, Mario Smarduch wrote:
> Patch adds  support for initial write protection VM memlsot. This patch series
            ^^                                    ^
stray whitespace                                 of

> assumes that huge PUDs will not be used in 2nd stage tables.

may be worth mentioning that this is always valid on ARMv7.

> 
> Signed-off-by: Mario Smarduch <[email-masked]>
> ---
>  arch/arm/include/asm/kvm_host.h       |    1 +
>  arch/arm/include/asm/kvm_mmu.h        |   20 ++++++
>  arch/arm/include/asm/pgtable-3level.h |    1 +
>  arch/arm/kvm/arm.c                    |    9 +++
>  arch/arm/kvm/mmu.c                    |  128 +++++++++++++++++++++++++++++++++
>  5 files changed, 159 insertions(+)
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 042206f..6521a2d 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -231,5 +231,6 @@ int kvm_perf_teardown(void);
>  u64 kvm_arm_timer_get_reg(struct kvm_vcpu *, u64 regid);
>  int kvm_arm_timer_set_reg(struct kvm_vcpu *, u64 regid, u64 value);
>  void kvm_arch_flush_remote_tlbs(struct kvm *);
> +void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>  
>  #endif /* __ARM_KVM_HOST_H__ */
> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> index 5cc0b0f..08ab5e8 100644
> --- a/arch/arm/include/asm/kvm_mmu.h
> +++ b/arch/arm/include/asm/kvm_mmu.h
> @@ -114,6 +114,26 @@ static inline void kvm_set_s2pmd_writable(pmd_t *pmd)
>  	pmd_val(*pmd) |= L_PMD_S2_RDWR;
>  }
>  
> +static inline void kvm_set_s2pte_readonly(pte_t *pte)
> +{
> +	pte_val(*pte) = (pte_val(*pte) & ~L_PTE_S2_RDWR) | L_PTE_S2_RDONLY;
> +}
> +
> +static inline bool kvm_s2pte_readonly(pte_t *pte)
> +{
> +	return (pte_val(*pte) & L_PTE_S2_RDWR) == L_PTE_S2_RDONLY;
> +}
> +
> +static inline void kvm_set_s2pmd_readonly(pmd_t *pmd)
> +{
> +	pmd_val(*pmd) = (pmd_val(*pmd) & ~L_PMD_S2_RDWR) | L_PMD_S2_RDONLY;
> +}
> +
> +static inline bool kvm_s2pmd_readonly(pmd_t *pmd)
> +{
> +	return (pmd_val(*pmd) & L_PMD_S2_RDWR) == L_PMD_S2_RDONLY;
> +}
> +
>  /* Open coded p*d_addr_end that can deal with 64bit addresses */
>  #define kvm_pgd_addr_end(addr, end)					\
>  ({	u64 __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK;		\
> diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
> index 85c60ad..d8bb40b 100644
> --- a/arch/arm/include/asm/pgtable-3level.h
> +++ b/arch/arm/include/asm/pgtable-3level.h
> @@ -129,6 +129,7 @@
>  #define L_PTE_S2_RDONLY			(_AT(pteval_t, 1) << 6)   /* HAP[1]   */
>  #define L_PTE_S2_RDWR			(_AT(pteval_t, 3) << 6)   /* HAP[2:1] */
>  
> +#define L_PMD_S2_RDONLY			(_AT(pteval_t, 1) << 6)   /* HAP[1]   */
>  #define L_PMD_S2_RDWR			(_AT(pmdval_t, 3) << 6)   /* HAP[2:1] */
>  
>  /*
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 3c82b37..e11c2dd 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -242,6 +242,15 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>  				   const struct kvm_memory_slot *old,
>  				   enum kvm_mr_change change)
>  {
> +#ifdef CONFIG_ARM
> +	/*
> +	 * At this point memslot has been committed and there is an
> +	 * allocated dirty_bitmap[], dirty pages will be be tracked while the
> +	 * memory slot is write protected.
> +	 */
> +	if ((change != KVM_MR_DELETE) && (mem->flags & KVM_MEM_LOG_DIRTY_PAGES))
> +		kvm_mmu_wp_memory_region(kvm, mem->slot);
> +#endif
>  }
>  
>  void kvm_arch_flush_shadow_all(struct kvm *kvm)
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 35254c6..7bfc792 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -763,6 +763,134 @@ static bool transparent_hugepage_adjust(pfn_t *pfnp, phys_addr_t *ipap)
>  	return false;
>  }
>  
> +#ifdef CONFIG_ARM
> +/**
> + * stage2_wp_pte_range - write protect PTE range
> + * @pmd:	pointer to pmd entry
> + * @addr:	range start address
> + * @end:	range end address
> + */
> +static void stage2_wp_pte_range(pmd_t *pmd, phys_addr_t addr, phys_addr_t end)
> +{
> +	pte_t *pte;
> +
> +	pte = pte_offset_kernel(pmd, addr);
> +	do {
> +		if (!pte_none(*pte)) {
> +			if (!kvm_s2pte_readonly(pte))
> +				kvm_set_s2pte_readonly(pte);
> +		}
> +	} while (pte++, addr += PAGE_SIZE, addr != end);
> +}
> +
> +/**
> + * stage2_wp_pmd_range - write protect PMD range
> + * @pud:	pointer to pud entry
> + * @addr:	range start address
> + * @end:	range end address
> + */
> +static void stage2_wp_pmd_range(pud_t *pud, phys_addr_t addr, phys_addr_t end)
> +{
> +	pmd_t *pmd;
> +	phys_addr_t next;
> +
> +	pmd = pmd_offset(pud, addr);
> +
> +	do {
> +		next = kvm_pmd_addr_end(addr, end);
> +		if (!pmd_none(*pmd)) {
> +			if (kvm_pmd_huge(*pmd)) {
> +				if (!kvm_s2pmd_readonly(pmd))
> +					kvm_set_s2pmd_readonly(pmd);
> +			} else
> +				stage2_wp_pte_range(pmd, addr, next);
please use a closing brace when the first part of the if-statement is a
multi-line block with braces, as per the CodingStyle.
> +

stray blank line

> +		}
> +	} while (pmd++, addr = next, addr != end);
> +}
> +
> +/**
> +  * stage2_wp_pud_range - write protect PUD range
> +  * @kvm:	pointer to kvm structure
> +  * @pud:	pointer to pgd entry
        pgd
> +  * @addr:	range start address
> +  * @end:	range end address
> +  *
> +  * While walking the PUD range huge PUD pages are ignored, in the future this
                             range, huge PUDs are ignored.  In the future...
> +  * may need to be revisited. Determine how to handle huge PUDs when logging
> +  * of dirty pages is enabled.

I don't understand the last sentence?

> +  */
> +static void  stage2_wp_pud_range(struct kvm *kvm, pgd_t *pgd,
> +				phys_addr_t addr, phys_addr_t end)
> +{
> +	pud_t *pud;
> +	phys_addr_t next;
> +
> +	pud = pud_offset(pgd, addr);
> +	do {
> +		next = kvm_pud_addr_end(addr, end);
> +		/* TODO: huge PUD not supported, revisit later */
> +		BUG_ON(pud_huge(*pud));

we should probably define kvm_pud_huge()

> +		if (!pud_none(*pud))
> +			stage2_wp_pmd_range(pud, addr, next);
> +	} while (pud++, addr = next, addr != end);
> +}
> +
> +/**
> + * stage2_wp_range() - write protect stage2 memory region range
> + * @kvm:	The KVM pointer
> + * @start:	Start address of range
> + * &end:	End address of range
> + */
> +static void stage2_wp_range(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
> +{
> +	pgd_t *pgd;
> +	phys_addr_t next;
> +
> +	pgd = kvm->arch.pgd + pgd_index(addr);
> +	do {
> +		/*
> +		 * Release kvm_mmu_lock periodically if the memory region is
> +		 * large features like detect hung task, lock detector or lock
                   large.  Otherwise, we may see panics due to..
> +		 * dep  may panic. In addition holding the lock this long will
    extra white space ^^           Additionally, holding the lock for a
    long timer will
> +		 * also starve other vCPUs. Applies to huge VM memory regions.
                                            ^^^ I don't understand this
					    last remark.
> +		 */
> +		if (need_resched() || spin_needbreak(&kvm->mmu_lock))
> +			cond_resched_lock(&kvm->mmu_lock);
> +
> +		next = kvm_pgd_addr_end(addr, end);
> +		if (pgd_present(*pgd))
> +			stage2_wp_pud_range(kvm, pgd, addr, next);
> +	} while (pgd++, addr = next, addr != end);
> +}
> +
> +/**
> + * kvm_mmu_wp_memory_region() - write protect stage 2 entries for memory slot
> + * @kvm:	The KVM pointer
> + * @slot:	The memory slot to write protect
> + *
> + * Called to start logging dirty pages after memory region
> + * KVM_MEM_LOG_DIRTY_PAGES operation is called. After this function returns
> + * all present PMD and PTEs are write protected in the memory region.
> + * Afterwards read of dirty page log can be called.
> + *
> + * Acquires kvm_mmu_lock. Called with kvm->slots_lock mutex acquired,
> + * serializing operations for VM memory regions.
> + */
> +
> +void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot)
> +{
> +	struct kvm_memory_slot *memslot = id_to_memslot(kvm->memslots, slot);
> +	phys_addr_t start = memslot->base_gfn << PAGE_SHIFT;
> +	phys_addr_t end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT;
> +
> +	spin_lock(&kvm->mmu_lock);
> +	stage2_wp_range(kvm, start, end);
> +	kvm_flush_remote_tlbs(kvm);
> +	spin_unlock(&kvm->mmu_lock);
> +}
> +#endif
> +
>  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  			  struct kvm_memory_slot *memslot,
>  			  unsigned long fault_status)
> -- 
> 1.7.9.5
> 

Besides the commenting and whitespace stuff, this is beginning to look
good.

Thanks,
-Christoffer