Re: [PATCH v14 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.

Kirti Wankhede
2020-03-19T18:57:43Z

On 3/19/2020 9:15 AM, Alex Williamson wrote:
> On Thu, 19 Mar 2020 01:11:11 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>
>> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
>> - Start dirty pages tracking while migration is active
>> - Stop dirty pages tracking.
>> - Get dirty pages bitmap. Its user space application's responsibility to
>> copy content of dirty pages from source to destination during migration.
>>
>> To prevent DoS attack, memory for bitmap is allocated per vfio_dma
>> structure. Bitmap size is calculated considering smallest supported page
>> size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled
>>
>> Bitmap is populated for already pinned pages when bitmap is allocated for
>> a vfio_dma with the smallest supported page size. Update bitmap from
>> pinning functions when tracking is enabled. When user application queries
>> bitmap, check if requested page size is same as page size used to
>> populated bitmap. If it is equal, copy bitmap, but if not equal, return
>> error.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>> Reviewed-by: Neo Jia <cjia@nvidia.com>
>> ---
>> drivers/vfio/vfio_iommu_type1.c | 205 +++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 203 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>> index 70aeab921d0f..d6417fb02174 100644
>> --- a/drivers/vfio/vfio_iommu_type1.c
>> +++ b/drivers/vfio/vfio_iommu_type1.c
>> @@ -71,6 +71,7 @@ struct vfio_iommu {
>> unsigned int dma_avail;
>> bool v2;
>> bool nesting;
>> + bool dirty_page_tracking;
>> };
>>
>> struct vfio_domain {
>> @@ -91,6 +92,7 @@ struct vfio_dma {
>> bool lock_cap; /* capable(CAP_IPC_LOCK) */
>> struct task_struct *task;
>> struct rb_root pfn_list; /* Ex-user pinned pfn list */
>> + unsigned long *bitmap;
>
> We've made the bitmap a width invariant u64 else, should be here as
> well.
>

Changing to u64 causes compile time warnings as below. Keeping 'unsigned
long *'

drivers/vfio/vfio_iommu_type1.c: In function ‘vfio_dma_bitmap_alloc_all’:
drivers/vfio/vfio_iommu_type1.c:232:8: warning: passing argument 1 of
‘bitmap_set’ from incompatible pointer type [enabled by default]
(vpfn->iova - dma->iova) / pgsize, 1);
^
In file included from ./include/linux/cpumask.h:12:0,
from ./arch/x86/include/asm/cpumask.h:5,
from ./arch/x86/include/asm/msr.h:11,
from ./arch/x86/include/asm/processor.h:22,
from ./arch/x86/include/asm/cpufeature.h:5,
from ./arch/x86/include/asm/thread_info.h:53,
from ./include/linux/thread_info.h:38,
from ./arch/x86/include/asm/preempt.h:7,
from ./include/linux/preempt.h:78,
from ./include/linux/spinlock.h:51,
from ./include/linux/seqlock.h:36,
from ./include/linux/time.h:6,
from ./include/linux/compat.h:10,
from drivers/vfio/vfio_iommu_type1.c:24:
./include/linux/bitmap.h:405:29: note: expected ‘long unsigned int *’
but argument is of type ‘u64 *’
static __always_inline void bitmap_set(unsigned long *map, unsigned
int start,

Thanks,
Kirti