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

Mario Smarduch
2014-08-12T00:16:31Z

On 08/11/2014 12:12 PM, Christoffer Dall wrote:
> Remove the parenthesis from the subject line.

Hmmm have to check this don't see it my patch file.
>
> 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
>
Need to watch out for these adds delays to review cycle.
>
>> assumes that huge PUDs will not be used in 2nd stage tables.
>
> may be worth mentioning that this is always valid on ARMv7.
>

Yep definitely.

>>
>> Signed-off-by: Mario Smarduch <m.smarduch@samsung.com>
>> ---
>> 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.
Will fix.
>> +
>
> stray blank line

Not sure how it got by checkpatch, will fix.
>
>> + }
>> + } 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?

Probably last two sentences should be combined.
".... to determine how to handle huge PUT...". Would that be
clear enough?

The overall theme is what to do about PUDs - mark all pages dirty
in the region, attempt to breakup such huge regions?

>
>> + */
>> +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()

Yep will add it.

>
>> + 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.

I'll clean it up for next iteration.
>
> Thanks,
> -Christoffer
>