Re: [PATCH v2 12/15] KVM: Provide common implementation for generic dirty log functions

Christoffer Dall
2019-10-23T09:29:30Z

On Mon, Oct 21, 2019 at 05:35:34PM -0700, Sean Christopherson wrote:
> Move the implementations of KVM_GET_DIRTY_LOG and KVM_CLEAR_DIRTY_LOG
> for CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT into common KVM code.
> The arch specific implemenations are extremely similar, differing
> only in whether the dirty log needs to be sync'd from hardware (x86)
> and how the TLBs are flushed. Add new arch hooks to handle sync
> and TLB flush; the sync will also be used for non-generic dirty log
> support in a future patch (s390).
>
> The ulterior motive for providing a common implementation is to
> eliminate the dependency between arch and common code with respect to
> the memslot referenced by the dirty log, i.e. to make it obvious in the
> code that the validity of the memslot is guaranteed, as a future patch
> will rework memslot handling such that id_to_memslot() can return NULL.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>

For the Arm parts:

Acked-by: Christoffer Dall <christoffer.dall@arm.com>

> ---
> arch/mips/kvm/mips.c | 62 ++---------------------------
> arch/powerpc/kvm/book3s.c | 5 +++
> arch/powerpc/kvm/booke.c | 5 +++
> arch/s390/kvm/kvm-s390.c | 5 +--
> arch/x86/kvm/x86.c | 60 ++--------------------------
> include/linux/kvm_host.h | 20 ++++------
> virt/kvm/arm/arm.c | 47 ++--------------------
> virt/kvm/kvm_main.c | 84 ++++++++++++++++++++++++++++++++-------
> 8 files changed, 99 insertions(+), 189 deletions(-)
>
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index 713e5465edb0..5c4feeeee447 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -965,69 +965,15 @@ long kvm_arch_vcpu_ioctl(struct file *filp, unsigned int ioctl,
> return r;
> }
>
> -/**
> - * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
> - * @kvm: kvm instance
> - * @log: slot id and address to which we copy the log
> - *
> - * Steps 1-4 below provide general overview of dirty page logging. See
> - * kvm_get_dirty_log_protect() function description for additional details.
> - *
> - * We call kvm_get_dirty_log_protect() to handle steps 1-3, upon return we
> - * always flush the TLB (step 4) even if previous step failed and the dirty
> - * bitmap may be corrupt. Regardless of previous outcome the KVM logging API
> - * does not preclude user space subsequent dirty log read. Flushing TLB ensures
> - * writes will be marked dirty for next log read.
> - *
> - * 1. Take a snapshot of the bit and clear it if needed.
> - * 2. Write protect the corresponding page.
> - * 3. Copy the snapshot to the userspace.
> - * 4. Flush TLB's if needed.
> - */
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> {
> - struct kvm_memslots *slots;
> - struct kvm_memory_slot *memslot;
> - bool flush = false;
> - int r;
>
> - mutex_lock(&kvm->slots_lock);
> -
> - r = kvm_get_dirty_log_protect(kvm, log, &flush);
> -
> - if (flush) {
> - slots = kvm_memslots(kvm);
> - memslot = id_to_memslot(slots, log->slot);
> -
> - /* Let implementation handle TLB/GVA invalidation */
> - kvm_mips_callbacks->flush_shadow_memslot(kvm, memslot);
> - }
> -
> - mutex_unlock(&kvm->slots_lock);
> - return r;
> }
>
> -int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm, struct kvm_clear_dirty_log *log)
> +void kvm_arch_dirty_log_tlb_flush(struct kvm *kvm, struct kvm_memory_slot *slot)
> {
> - struct kvm_memslots *slots;
> - struct kvm_memory_slot *memslot;
> - bool flush = false;
> - int r;
> -
> - mutex_lock(&kvm->slots_lock);
> -
> - r = kvm_clear_dirty_log_protect(kvm, log, &flush);
> -
> - if (flush) {
> - slots = kvm_memslots(kvm);
> - memslot = id_to_memslot(slots, log->slot);
> -
> - /* Let implementation handle TLB/GVA invalidation */
> - kvm_mips_callbacks->flush_shadow_memslot(kvm, memslot);
> - }
> -
> - mutex_unlock(&kvm->slots_lock);
> - return r;
> + /* Let implementation handle TLB/GVA invalidation */
> + kvm_mips_callbacks->flush_shadow_memslot(kvm, memslot);
> }
>
> long kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
> index a5d4a1014fdf..84f66c1592a3 100644
> --- a/arch/powerpc/kvm/book3s.c
> +++ b/arch/powerpc/kvm/book3s.c
> @@ -829,6 +829,11 @@ int kvmppc_core_check_requests(struct kvm_vcpu *vcpu)
> return vcpu->kvm->arch.kvm_ops->check_requests(vcpu);
> }
>
> +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> +{
> +
> +}
> +
> int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> {
> return kvm->arch.kvm_ops->get_dirty_log(kvm, log);
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index a22ff567724a..35a4ef89a1db 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -1796,6 +1796,11 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
> return r;
> }
>
> +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> +{
> +
> +}
> +
> int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> {
> return -ENOTSUPP;
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 21f61dae7db1..c0e9929bdb34 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -572,8 +572,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> return r;
> }
>
> -static void kvm_s390_sync_dirty_log(struct kvm *kvm,
> - struct kvm_memory_slot *memslot)
> +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> {
> int i;
> gfn_t cur_gfn, last_gfn;
> @@ -633,7 +632,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
> if (!memslot->dirty_bitmap)
> goto out;
>
> - kvm_s390_sync_dirty_log(kvm, memslot);
> + kvm_arch_sync_dirty_log(kvm, memslot);
> r = kvm_get_dirty_log(kvm, log, &is_dirty);
> if (r)
> goto out;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index adf384ef5969..3d3d70aac031 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4615,77 +4615,23 @@ static int kvm_vm_ioctl_reinject(struct kvm *kvm,
> return 0;
> }
>
> -/**
> - * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
> - * @kvm: kvm instance
> - * @log: slot id and address to which we copy the log
> - *
> - * Steps 1-4 below provide general overview of dirty page logging. See
> - * kvm_get_dirty_log_protect() function description for additional details.
> - *
> - * We call kvm_get_dirty_log_protect() to handle steps 1-3, upon return we
> - * always flush the TLB (step 4) even if previous step failed and the dirty
> - * bitmap may be corrupt. Regardless of previous outcome the KVM logging API
> - * does not preclude user space subsequent dirty log read. Flushing TLB ensures
> - * writes will be marked dirty for next log read.
> - *
> - * 1. Take a snapshot of the bit and clear it if needed.
> - * 2. Write protect the corresponding page.
> - * 3. Copy the snapshot to the userspace.
> - * 4. Flush TLB's if needed.
> - */
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> {
> - bool flush = false;
> - int r;
> -
> - mutex_lock(&kvm->slots_lock);
> -
> /*
> * Flush potentially hardware-cached dirty pages to dirty_bitmap.
> */
> if (kvm_x86_ops->flush_log_dirty)
> kvm_x86_ops->flush_log_dirty(kvm);
> -
> - r = kvm_get_dirty_log_protect(kvm, log, &flush);
> -
> - /*
> - * All the TLBs can be flushed out of mmu lock, see the comments in
> - * kvm_mmu_slot_remove_write_access().
> - */
> - lockdep_assert_held(&kvm->slots_lock);
> - if (flush)
> - kvm_flush_remote_tlbs(kvm);
> -
> - mutex_unlock(&kvm->slots_lock);
> - return r;
> }
>
> -int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm, struct kvm_clear_dirty_log *log)
> +void kvm_arch_dirty_log_tlb_flush(struct kvm *kvm, struct kvm_memory_slot *slot)
> {
> - bool flush = false;
> - int r;
> -
> - mutex_lock(&kvm->slots_lock);
> -
> - /*
> - * Flush potentially hardware-cached dirty pages to dirty_bitmap.
> - */
> - if (kvm_x86_ops->flush_log_dirty)
> - kvm_x86_ops->flush_log_dirty(kvm);
> -
> - r = kvm_clear_dirty_log_protect(kvm, log, &flush);
> -
> /*
> * All the TLBs can be flushed out of mmu lock, see the comments in
> * kvm_mmu_slot_remove_write_access().
> */
> lockdep_assert_held(&kvm->slots_lock);
> - if (flush)
> - kvm_flush_remote_tlbs(kvm);
> -
> - mutex_unlock(&kvm->slots_lock);
> - return r;
> + kvm_flush_remote_tlbs(kvm);
> }
>
> int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_event,
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index bfb8194d0366..80dd823a1a8b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -797,23 +797,19 @@ vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf);
>
> int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext);
>
> -int kvm_get_dirty_log(struct kvm *kvm,
> - struct kvm_dirty_log *log, int *is_dirty);
> -
> -int kvm_get_dirty_log_protect(struct kvm *kvm,
> - struct kvm_dirty_log *log, bool *flush);
> -int kvm_clear_dirty_log_protect(struct kvm *kvm,
> - struct kvm_clear_dirty_log *log, bool *flush);
> -
> void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
> struct kvm_memory_slot *slot,
> gfn_t gfn_offset,
> unsigned long mask);
> +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot);
>
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
> - struct kvm_dirty_log *log);
> -int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
> - struct kvm_clear_dirty_log *log);
> +#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> +void kvm_arch_dirty_log_tlb_flush(struct kvm *kvm, struct kvm_memory_slot *slot);
> +#else /* !CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
> +int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log);
> +int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log,
> + int *is_dirty);
> +#endif
>
> int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
> bool line_status);
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 86c6aa1cb58e..03f668e812ea 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -1203,55 +1203,14 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
> return r;
> }
>
> -/**
> - * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
> - * @kvm: kvm instance
> - * @log: slot id and address to which we copy the log
> - *
> - * Steps 1-4 below provide general overview of dirty page logging. See
> - * kvm_get_dirty_log_protect() function description for additional details.
> - *
> - * We call kvm_get_dirty_log_protect() to handle steps 1-3, upon return we
> - * always flush the TLB (step 4) even if previous step failed and the dirty
> - * bitmap may be corrupt. Regardless of previous outcome the KVM logging API
> - * does not preclude user space subsequent dirty log read. Flushing TLB ensures
> - * writes will be marked dirty for next log read.
> - *
> - * 1. Take a snapshot of the bit and clear it if needed.
> - * 2. Write protect the corresponding page.
> - * 3. Copy the snapshot to the userspace.
> - * 4. Flush TLB's if needed.
> - */
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
> {
> - bool flush = false;
> - int r;
>
> - mutex_lock(&kvm->slots_lock);
> -
> - r = kvm_get_dirty_log_protect(kvm, log, &flush);
> -
> - if (flush)
> - kvm_flush_remote_tlbs(kvm);
> -
> - mutex_unlock(&kvm->slots_lock);
> - return r;
> }
>
> -int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm, struct kvm_clear_dirty_log *log)
> +void kvm_arch_dirty_log_tlb_flush(struct kvm *kvm, struct kvm_memory_slot *slot)
> {
> - bool flush = false;
> - int r;
> -
> - mutex_lock(&kvm->slots_lock);
> -
> - r = kvm_clear_dirty_log_protect(kvm, log, &flush);
> -
> - if (flush)
> - kvm_flush_remote_tlbs(kvm);
> -
> - mutex_unlock(&kvm->slots_lock);
> - return r;
> + kvm_flush_remote_tlbs(kvm);
> }
>
> static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index c3e481986099..c0ce5081dd00 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -781,7 +781,7 @@ static int kvm_vm_release(struct inode *inode, struct file *filp)
>
> /*
> * Allocation size is twice as large as the actual dirty bitmap size.
> - * See x86's kvm_vm_ioctl_get_dirty_log() why this is needed.
> + * See kvm_vm_ioctl_get_dirty_log() why this is needed.
> */
> static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
> {
> @@ -1123,6 +1123,7 @@ static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
> return kvm_set_memory_region(kvm, mem);
> }
>
> +#ifndef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> int kvm_get_dirty_log(struct kvm *kvm,
> struct kvm_dirty_log *log, int *is_dirty)
> {
> @@ -1156,13 +1157,12 @@ int kvm_get_dirty_log(struct kvm *kvm,
> }
> EXPORT_SYMBOL_GPL(kvm_get_dirty_log);
>
> -#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> +#else /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
> /**
> * kvm_get_dirty_log_protect - get a snapshot of dirty pages
> * and reenable dirty page tracking for the corresponding pages.
> * @kvm: pointer to kvm instance
> * @log: slot id and address to which we copy the log
> - * @flush: true if TLB flush is needed by caller
> *
> * We need to keep it in mind that VCPU threads can write to the bitmap
> * concurrently. So, to avoid losing track of dirty pages we keep the
> @@ -1179,8 +1179,7 @@ EXPORT_SYMBOL_GPL(kvm_get_dirty_log);
> * exiting to userspace will be logged for the next call.
> *
> */
> -int kvm_get_dirty_log_protect(struct kvm *kvm,
> - struct kvm_dirty_log *log, bool *flush)
> +static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log)
> {
> struct kvm_memslots *slots;
> struct kvm_memory_slot *memslot;
> @@ -1188,6 +1187,7 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
> unsigned long n;
> unsigned long *dirty_bitmap;
> unsigned long *dirty_bitmap_buffer;
> + bool flush;
>
> as_id = log->slot >> 16;
> id = (u16)log->slot;
> @@ -1201,8 +1201,10 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
> if (!dirty_bitmap)
> return -ENOENT;
>
> + kvm_arch_sync_dirty_log(kvm, memslot);
> +
> n = kvm_dirty_bitmap_bytes(memslot);
> - *flush = false;
> + flush = false;
> if (kvm->manual_dirty_log_protect) {
> /*
> * Unlike kvm_get_dirty_log, we always return false in *flush,
> @@ -1225,7 +1227,7 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
> if (!dirty_bitmap[i])
> continue;
>
> - *flush = true;
> + flush = true;
> mask = xchg(&dirty_bitmap[i], 0);
> dirty_bitmap_buffer[i] = mask;
>
> @@ -1236,21 +1238,55 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
> spin_unlock(&kvm->mmu_lock);
> }
>
> + if (flush)
> + kvm_arch_dirty_log_tlb_flush(kvm, memslot);
> +
> if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
> return -EFAULT;
> return 0;
> }
> -EXPORT_SYMBOL_GPL(kvm_get_dirty_log_protect);
> +
> +
> +/**
> + * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
> + * @kvm: kvm instance
> + * @log: slot id and address to which we copy the log
> + *
> + * Steps 1-4 below provide general overview of dirty page logging. See
> + * kvm_get_dirty_log_protect() function description for additional details.
> + *
> + * We call kvm_get_dirty_log_protect() to handle steps 1-3, upon return we
> + * always flush the TLB (step 4) even if previous step failed and the dirty
> + * bitmap may be corrupt. Regardless of previous outcome the KVM logging API
> + * does not preclude user space subsequent dirty log read. Flushing TLB ensures
> + * writes will be marked dirty for next log read.
> + *
> + * 1. Take a snapshot of the bit and clear it if needed.
> + * 2. Write protect the corresponding page.
> + * 3. Copy the snapshot to the userspace.
> + * 4. Flush TLB's if needed.
> + */
> +static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
> + struct kvm_dirty_log *log)
> +{
> + int r;
> +
> + mutex_lock(&kvm->slots_lock);
> +
> + r = kvm_get_dirty_log_protect(kvm, log);
> +
> + mutex_unlock(&kvm->slots_lock);
> + return r;
> +}
>
> /**
> * kvm_clear_dirty_log_protect - clear dirty bits in the bitmap
> * and reenable dirty page tracking for the corresponding pages.
> * @kvm: pointer to kvm instance
> * @log: slot id and address from which to fetch the bitmap of dirty pages
> - * @flush: true if TLB flush is needed by caller
> */
> -int kvm_clear_dirty_log_protect(struct kvm *kvm,
> - struct kvm_clear_dirty_log *log, bool *flush)
> +static int kvm_clear_dirty_log_protect(struct kvm *kvm,
> + struct kvm_clear_dirty_log *log)
> {
> struct kvm_memslots *slots;
> struct kvm_memory_slot *memslot;
> @@ -1259,6 +1295,7 @@ int kvm_clear_dirty_log_protect(struct kvm *kvm,
> unsigned long i, n;
> unsigned long *dirty_bitmap;
> unsigned long *dirty_bitmap_buffer;
> + bool flush;
>
> as_id = log->slot >> 16;
> id = (u16)log->slot;
> @@ -1282,7 +1319,9 @@ int kvm_clear_dirty_log_protect(struct kvm *kvm,
> (log->num_pages < memslot->npages - log->first_page && (log->num_pages & 63)))
> return -EINVAL;
>
> - *flush = false;
> + kvm_arch_sync_dirty_log(kvm, memslot);
> +
> + flush = false;
> dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
> if (copy_from_user(dirty_bitmap_buffer, log->dirty_bitmap, n))
> return -EFAULT;
> @@ -1305,17 +1344,32 @@ int kvm_clear_dirty_log_protect(struct kvm *kvm,
> * a problem if userspace sets them in log->dirty_bitmap.
> */
> if (mask) {
> - *flush = true;
> + flush = true;
> kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
> offset, mask);
> }
> }
> spin_unlock(&kvm->mmu_lock);
>
> + if (flush)
> + kvm_arch_dirty_log_tlb_flush(kvm, memslot);
> +
> return 0;
> }
> -EXPORT_SYMBOL_GPL(kvm_clear_dirty_log_protect);
> -#endif
> +
> +static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
> + struct kvm_clear_dirty_log *log)
> +{
> + int r;
> +
> + mutex_lock(&kvm->slots_lock);
> +
> + r = kvm_clear_dirty_log_protect(kvm, log);
> +
> + mutex_unlock(&kvm->slots_lock);
> + return r;
> +}
> +#endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
>
> bool kvm_largepages_enabled(void)
> {
> --
> 2.22.0
>
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