Use the proper API instead.
Fixes: f440c8a572d7 ("drm/i915/gvt/kvmgt: read/write GPA via KVM API")
Signed-off-by: Christoph Hellwig <[email protected]>
---
drivers/gpu/drm/i915/gvt/kvmgt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 074c4efb58eb..5848400620b4 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -2037,7 +2037,7 @@ static int kvmgt_rw_gpa(unsigned long handle, unsigned long gpa,
struct kvmgt_guest_info *info;
struct kvm *kvm;
int idx, ret;
- bool kthread = current->mm == NULL;
+ bool kthread = (current->flags & PF_KTHREAD);
if (!handle_valid(handle))
return -ESRCH;
--
2.25.1
Hello!
On 04.04.2020 12:40, Christoph Hellwig wrote:
> Use the proper API instead.
>
> Fixes: f440c8a572d7 ("drm/i915/gvt/kvmgt: read/write GPA via KVM API")
> Signed-off-by: Christoph Hellwig <[email protected]>
> ---
> drivers/gpu/drm/i915/gvt/kvmgt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 074c4efb58eb..5848400620b4 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -2037,7 +2037,7 @@ static int kvmgt_rw_gpa(unsigned long handle, unsigned long gpa,
> struct kvmgt_guest_info *info;
> struct kvm *kvm;
> int idx, ret;
> - bool kthread = current->mm == NULL;
> + bool kthread = (current->flags & PF_KTHREAD);
Don't need the parens.
[...]
MBR, Sergei
On Sat, Apr 04, 2020 at 11:40:57AM +0200, Christoph Hellwig wrote:
> Use the proper API instead.
>
> Fixes: f440c8a572d7 ("drm/i915/gvt/kvmgt: read/write GPA via KVM API")
> Signed-off-by: Christoph Hellwig <[email protected]>
> ---
> drivers/gpu/drm/i915/gvt/kvmgt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 074c4efb58eb..5848400620b4 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -2037,7 +2037,7 @@ static int kvmgt_rw_gpa(unsigned long handle, unsigned long gpa,
> struct kvmgt_guest_info *info;
> struct kvm *kvm;
> int idx, ret;
> - bool kthread = current->mm == NULL;
> + bool kthread = (current->flags & PF_KTHREAD);
>
> if (!handle_valid(handle))
> return -ESRCH;
> --
> 2.25.1
>
hi
we were removing this code. see
https://lore.kernel.org/kvm/[email protected]/
The implementation of vfio_dma_rw() has been in vfio next tree.
https://github.com/awilliam/linux-vfio/commit/8d46c0cca5f4dc0538173d62cd36b1119b5105bc
in vfio_dma_rw(), we still use
bool kthread = current->mm == NULL.
because if current->mm != NULL and current->flags & PF_KTHREAD, instead
of calling use_mm(), we first check if (current->mm == mm) and allow copy_to_user() if it's true.
Do you think it's all right?
Thanks
Yan
> _______________________________________________
> intel-gvt-dev mailing list
> [email protected]
> https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev
On Mon, Apr 06, 2020 at 11:08:46PM -0400, Yan Zhao wrote:
> hi
> we were removing this code. see
> https://lore.kernel.org/kvm/[email protected]/
This didn't make 5.7-rc1.
> The implementation of vfio_dma_rw() has been in vfio next tree.
> https://github.com/awilliam/linux-vfio/commit/8d46c0cca5f4dc0538173d62cd36b1119b5105bc
This made 5.7-rc1, so I'll update the series to take it into account.
T
> in vfio_dma_rw(), we still use
> bool kthread = current->mm == NULL.
> because if current->mm != NULL and current->flags & PF_KTHREAD, instead
> of calling use_mm(), we first check if (current->mm == mm) and allow copy_to_user() if it's true.
>
> Do you think it's all right?
I can't think of another way for a kernel thread to have a mm indeed.
On Mon, Apr 13, 2020 at 03:27:30PM +0200, Christoph Hellwig wrote:
> On Mon, Apr 06, 2020 at 11:08:46PM -0400, Yan Zhao wrote:
> > hi
> > we were removing this code. see
> > https://lore.kernel.org/kvm/[email protected]/
>
> This didn't make 5.7-rc1.
>
> > The implementation of vfio_dma_rw() has been in vfio next tree.
> > https://github.com/awilliam/linux-vfio/commit/8d46c0cca5f4dc0538173d62cd36b1119b5105bc
>
>
> This made 5.7-rc1, so I'll update the series to take it into account.
>
> T
> > in vfio_dma_rw(), we still use
> > bool kthread = current->mm == NULL.
> > because if current->mm != NULL and current->flags & PF_KTHREAD, instead
> > of calling use_mm(), we first check if (current->mm == mm) and allow copy_to_user() if it's true.
> >
> > Do you think it's all right?
>
> I can't think of another way for a kernel thread to have a mm indeed.
for example, before calling to vfio_dma_rw(), a kernel thread has already
called use_mm(), then its current->mm is not null, and it has flag
PF_KTHREAD.
in this case, we just want to allow the copy_to_user() directly if
current->mm == mm, rather than call another use_mm() again.
do you think it makes sense?
Thanks
Yan
> _______________________________________________
> intel-gvt-dev mailing list
> [email protected]
> https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev
On Mon, Apr 13, 2020 at 08:04:10PM -0400, Yan Zhao wrote:
> > I can't think of another way for a kernel thread to have a mm indeed.
> for example, before calling to vfio_dma_rw(), a kernel thread has already
> called use_mm(), then its current->mm is not null, and it has flag
> PF_KTHREAD.
> in this case, we just want to allow the copy_to_user() directly if
> current->mm == mm, rather than call another use_mm() again.
>
> do you think it makes sense?
I mean no other way than using use_mm. That being said nesting
potentional use_mm callers sounds like a rather bad idea, and we
should avoid that.
On Tue, Apr 14, 2020 at 09:00:13AM +0200, Christoph Hellwig wrote:
> On Mon, Apr 13, 2020 at 08:04:10PM -0400, Yan Zhao wrote:
> > > I can't think of another way for a kernel thread to have a mm indeed.
> > for example, before calling to vfio_dma_rw(), a kernel thread has already
> > called use_mm(), then its current->mm is not null, and it has flag
> > PF_KTHREAD.
> > in this case, we just want to allow the copy_to_user() directly if
> > current->mm == mm, rather than call another use_mm() again.
> >
> > do you think it makes sense?
>
> I mean no other way than using use_mm. That being said nesting
> potentional use_mm callers sounds like a rather bad idea, and we
> should avoid that.
yes, agree.
I was explaining why we just use "current->mm == NULL"
(not "current->flag & PF_KTHREAD") as a criteria to call use_mm()
in vfio_dma_rw(), which you might ask us when you take that part into your
series. :)