Hi Paolo,
I took a closer look at Christoffers comment,
the _log description in x86.c is a repeat of the
_protect description in kvm_main.c.
I'm wondering if description below would be acceptable, or
perhaps you had a reason leaving it as is.
For the ARM variant I would word same. Please advise.
Thanks.
"
/**
* 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 'protect' failed and dirty bitmap
* may be corrupt. Regardless of previous outcome KVM logging API does not
* preclude user space subsequent dirty log read. Flushing TLB insures
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.
*/
"
On 11/22/2014 11:19 AM, Christoffer Dall wrote:
> On Thu, Nov 13, 2014 at 05:57:44PM -0800, Mario Smarduch wrote:
>> From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>>
>> We now have a generic function that does most of the work of
>> kvm_vm_ioctl_get_dirty_log, now use it.
>>
>> Signed-off-by: Mario Smarduch <m.smarduch@xxxxxxxxxxx>
>> ---
>> arch/x86/include/asm/kvm_host.h | 3 --
>> arch/x86/kvm/Kconfig | 1 +
>> arch/x86/kvm/mmu.c | 4 +--
>> arch/x86/kvm/x86.c | 64 ++++++---------------------------------
>> 4 files changed, 12 insertions(+), 60 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 7c492ed..934dc24 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -805,9 +805,6 @@ void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
>>
>> void kvm_mmu_reset_context(struct kvm_vcpu *vcpu);
>> void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot);
>> -void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
>> - struct kvm_memory_slot *slot,
>> - gfn_t gfn_offset, unsigned long mask);
>> void kvm_mmu_zap_all(struct kvm *kvm);
>> void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm);
>> unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm);
>> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
>> index f9d16ff..d073594 100644
>> --- a/arch/x86/kvm/Kconfig
>> +++ b/arch/x86/kvm/Kconfig
>> @@ -39,6 +39,7 @@ config KVM
>> select PERF_EVENTS
>> select HAVE_KVM_MSI
>> select HAVE_KVM_CPU_RELAX_INTERCEPT
>> + select KVM_GENERIC_DIRTYLOG_READ_PROTECT
>> select KVM_VFIO
>> ---help---
>> Support hosting fully virtualized guest machines using hardware
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index 9314678..bf6b82c 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -1224,7 +1224,7 @@ static bool __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp,
>> }
>>
>> /**
>> - * kvm_mmu_write_protect_pt_masked - write protect selected PT level pages
>> + * kvm_arch_mmu_write_protect_pt_masked - write protect selected PT level pages
>> * @kvm: kvm instance
>> * @slot: slot to protect
>> * @gfn_offset: start of the BITS_PER_LONG pages we care about
>> @@ -1233,7 +1233,7 @@ static bool __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp,
>> * Used when we do not need to care about huge page mappings: e.g. during dirty
>> * logging we do not have any such mappings.
>> */
>> -void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
>> +void kvm_arch_mmu_write_protect_pt_masked(struct kvm *kvm,
>> struct kvm_memory_slot *slot,
>> gfn_t gfn_offset, unsigned long mask)
>> {
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 8f1e22d..9f8ae9a 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -3606,77 +3606,31 @@ static int kvm_vm_ioctl_reinject(struct kvm *kvm,
>> *
>> * 1. Take a snapshot of the bit and clear it if needed.
>> * 2. Write protect the corresponding page.
>> - * 3. Flush TLB's if needed.
>> - * 4. Copy the snapshot to the userspace.
>> + * 3. Copy the snapshot to the userspace.
>> + * 4. Flush TLB's if needed.
>> *
>> - * Between 2 and 3, the guest may write to the page using the remaining TLB
>> - * entry. This is not a problem because the page will be reported dirty at
>> - * step 4 using the snapshot taken before and step 3 ensures that successive
>> - * writes will be logged for the next call.
>> + * Between 2 and 4, the guest may write to the page using the remaining TLB
>> + * entry. This is not a problem because the page is reported dirty using
>> + * the snapshot taken before and step 4 ensures that writes done after
>> + * exiting to userspace will be logged for the next call.
>> */
>
> this seems to duplicate the comment in virt/kvm/kvm_main.c, but
> whatever.
>
> FWIW:
> Acked-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
>
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