Subject: [PATCH v13 5/7] arm: KVM: Add initial dirty page locking infrastructure

From: [email-masked] (Mario Smarduch)
Date: Fri, 07 Nov 2014 11:07:17 -0800

On 11/07/2014 02:15 AM, Marc Zyngier wrote:
> On 07/11/14 00:40, Mario Smarduch wrote:
>> Add support for initial write protection of VM memlsot. This patch
>                                                  memslots
>> series assumes that huge PUDs will not be used in 2nd stage tables, which is
>> awlays valid on ARMv7.
>   always
Spell checks still - will update.
>>
>> Signed-off-by: Mario Smarduch <[email-masked]>
>> ---
>>  arch/arm/include/asm/kvm_host.h       |    2 +
>>  arch/arm/include/asm/kvm_mmu.h        |   20 +++++
>>  arch/arm/include/asm/pgtable-3level.h |    1 +
>>  arch/arm/kvm/mmu.c                    |  140 +++++++++++++++++++++++++++++++++
>>  4 files changed, 163 insertions(+)
>>
>> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
>> index fad598c..72510ca 100644
>> --- a/arch/arm/include/asm/kvm_host.h
>> +++ b/arch/arm/include/asm/kvm_host.h
>> @@ -245,4 +245,6 @@ static inline void vgic_arch_setup(const struct vgic_params *vgic)
>>  int kvm_perf_init(void);
>>  int kvm_perf_teardown(void);
>>  
>> +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 06e0bc0..d29c880 100644
>> --- a/arch/arm/include/asm/pgtable-3level.h
>> +++ b/arch/arm/include/asm/pgtable-3level.h
>> @@ -130,6 +130,7 @@
>>  #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(pmdval_t, 1) << 6)   /* HAP[1]   */
>>  #define L_PMD_S2_RDWR			(_AT(pmdval_t, 3) << 6)   /* HAP[2:1] */
>>  
>>  /*
>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>> index 16e7994..3b86522 100644
>> --- a/arch/arm/kvm/mmu.c
>> +++ b/arch/arm/kvm/mmu.c
>> @@ -45,6 +45,7 @@ static phys_addr_t hyp_idmap_vector;
>>  #define pgd_order get_order(PTRS_PER_PGD * sizeof(pgd_t))
>>  
>>  #define kvm_pmd_huge(_x)	(pmd_huge(_x) || pmd_trans_huge(_x))
>> +#define kvm_pud_huge(_x)	pud_huge(_x)
>>  
>>  static void kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa)
>>  {
>> @@ -746,6 +747,133 @@ static bool transparent_hugepage_adjust(pfn_t *pfnp, phys_addr_t *ipap)
>>  	return false;
>>  }
>>  
>> +#ifdef CONFIG_ARM
>> +/**
>> + * stage2_wp_ptes - write protect PMD range
>> + * @pmd:	pointer to pmd entry
>> + * @addr:	range start address
>> + * @end:	range end address
>> + */
>> +static void stage2_wp_ptes(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_pmds - write protect PUD range
>> + * @pud:	pointer to pud entry
>> + * @addr:	range start address
>> + * @end:	range end address
>> + */
>> +static void stage2_wp_pmds(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_ptes(pmd, addr, next);
>> +			}
>> +		}
>> +	} while (pmd++, addr = next, addr != end);
>> +}
>> +
>> +/**
>> +  * stage2_wp_puds - write protect PGD range
>> +  * @kvm:	pointer to kvm structure
>> +  * @pud:	pointer to pgd entry
>> +  * @addr:	range start address
>> +  * @end:	range end address
>> +  *
>> +  * While walking the PUD range huge PUD pages are ignored.
> 
> Well, not really. Huge PUDs are actually triggering a kernel panic.

Yes will rephrase, it doesn't just dismiss the condition.
Left over from earlier version where we failed on the ioctl
during initial write protect, but even then it still failed.
> 
>> +  */
>> +static void  stage2_wp_puds(struct kvm *kvm, pgd_t *pgd,
> 
> Why do we have a "kvm" parameter here?

That's again left over from an early version where we needed it
while breaking up huge pages, will remove it.
> 
>> +					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);
>> +		if (!pud_none(*pud)) {
>> +			/* TODO:PUD not supported, revisit later if supported */
>> +			BUG_ON(kvm_pud_huge(*pud));
>> +			stage2_wp_pmds(pud, addr, next);
>> +		}
>> +	} while (pud++, addr = next, addr != end);
>> +}
>> +
>> +/**
>> + * stage2_wp_range() - write protect stage2 memory region range
>> + * @kvm:	The KVM pointer
>> + * @addr:	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. Otherwise, we may see kernel panics with
>> +		 * CONFIG_DETECT_HUNG_TASK, CONFIG_LOCK_DETECTOR,
>> +		 * CONFIG_LOCK_DEP. Additionally, holding the lock too long
>> +		 * will also starve other vCPUs.
>> +		 */
>> +		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_puds(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);
>> +	spin_unlock(&kvm->mmu_lock);
>> +	kvm_flush_remote_tlbs(kvm);
>> +}
>> +#endif
>> +
>>  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>  			  struct kvm_memory_slot *memslot,
>>  			  unsigned long fault_status)
>> @@ -1129,6 +1257,18 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>>  		unmap_stage2_range(kvm, gpa, size);
>>  		spin_unlock(&kvm->mmu_lock);
>>  	}
>> +
>> +#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) && change != KVM_MR_MOVE &&
> 
> [nit] extraneous set of parenthesis.
> 
>> +					(mem->flags & KVM_MEM_LOG_DIRTY_PAGES))
Will change.
>> +		kvm_mmu_wp_memory_region(kvm, mem->slot);
>> +#endif
>> +
>>  }
>>  
>>  int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>
> 
> Thanks,
> 
> 	M.
>