Re: [PATCH v13 2/7] KVM: Add generic support for dirty page logging

Mario Smarduch
2014-11-07T18:55:15Z

On 11/07/2014 01:07 AM, Cornelia Huck wrote:
> On Thu, 06 Nov 2014 16:40:43 -0800
> Mario Smarduch <m.smarduch@samsung.com> wrote:
>
>> kvm_get_dirty_log() provides generic handling of dirty bitmap, currently reused
>> by several architectures. Building on that we intrdoduce
>> kvm_get_dirty_log_protect() adding write protection to mark these pages dirty
>> for future write access, before next KVM_GET_DIRTY_LOG ioctl call from user
>> space.
>>
>> Signed-off-by: Mario Smarduch <m.smarduch@samsung.com>
>> ---
>> include/linux/kvm_host.h | 9 +++++
>> virt/kvm/kvm_main.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 104 insertions(+)
>>
>
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 887df87..f017760 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -981,6 +981,101 @@ out:
>> }
>> EXPORT_SYMBOL_GPL(kvm_get_dirty_log);
>>
>> +#if defined(CONFIG_S390) || defined(CONFIG_PPC) || defined(CONFIG_MIPS) || \
>> + defined(CONFIG_IA64) || defined(CONFIG_X86) || defined(CONFIG_ARM) || \
>> + defined(CONFIG_ARM64)
>
> Does this deserve a config symbol that can be selected by architectures
> actually using kvm_get_dirty_log_protect()? I.e.,
>
> #ifndef CONFIG_KVM_ARCH_DIRTY_LOG_PROTECT
>
> or so?

Yes definitely, not sure why I went this way after using Kconfig
defines before.

>
>> +/*
>> + * For architectures that don't use kvm_get_dirty_log_protect() for dirty page
>> + * logging, calling this function is illegal. Otherwise the function is defined
>> + * in arch subtree and this restriction is removed.
>> + */
>
> What about
>
> /*
> * For architectures that don't use kvm_get_dirty_log_protect() for dirty page
> * logging, we must never end up calling this function. Architectures that do
> * use it define their own version of this function.
> */
>
> instead

Yeah that reads better, getting the illegal out of there.
>
>> +void kvm_arch_mmu_write_protect_pt_masked(struct kvm *kvm,
>> + struct kvm_memory_slot *slot,
>> + gfn_t gfn_offset,
>> + unsigned long mask)
>> +{
>> + BUG();
>> +}
>> +#endif
>> +
> (...)
>