vfio/type1: optimize vfio_pin_pages_remote() and vfio_unpin_pages_remote() for large folio

[PATCH 2/4] vfio/type1: batch vfio_find_vpfn() in function vfio_unpin_pages_remote()

Posted by lizhe.67@bytedance.com 7 months, 2 weeks ago

From: Li Zhe <lizhe.67@bytedance.com>

The function vpfn_pages() can help us determine the number of vpfn
nodes on the vpfn rb tree within a specified range. This allows us
to avoid searching for each vpfn individually in the function
vfio_unpin_pages_remote(). This patch batches the vfio_find_vpfn()
calls in function vfio_unpin_pages_remote().

Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
---
 drivers/vfio/vfio_iommu_type1.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index a2d7abd4f2c2..330fff4fe96d 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -804,16 +804,12 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
 				    unsigned long pfn, unsigned long npage,
 				    bool do_accounting)
 {
-	long unlocked = 0, locked = 0;
+	long unlocked = 0, locked = vpfn_pages(dma, iova, npage);
 	long i;
 
-	for (i = 0; i < npage; i++, iova += PAGE_SIZE) {
-		if (put_pfn(pfn++, dma->prot)) {
+	for (i = 0; i < npage; i++)
+		if (put_pfn(pfn++, dma->prot))
 			unlocked++;
-			if (vfio_find_vpfn(dma, iova))
-				locked++;
-		}
-	}
 
 	if (do_accounting)
 		vfio_lock_acct(dma, locked - unlocked, true);
-- 
2.20.1

Re: [PATCH 2/4] vfio/type1: batch vfio_find_vpfn() in function vfio_unpin_pages_remote()

Posted by Jason Gunthorpe 7 months, 1 week ago

On Mon, Jun 30, 2025 at 03:25:16PM +0800, lizhe.67@bytedance.com wrote:
> From: Li Zhe <lizhe.67@bytedance.com>
> 
> The function vpfn_pages() can help us determine the number of vpfn
> nodes on the vpfn rb tree within a specified range. This allows us
> to avoid searching for each vpfn individually in the function
> vfio_unpin_pages_remote(). This patch batches the vfio_find_vpfn()
> calls in function vfio_unpin_pages_remote().
> 
> Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index a2d7abd4f2c2..330fff4fe96d 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -804,16 +804,12 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
>  				    unsigned long pfn, unsigned long npage,
>  				    bool do_accounting)
>  {
> -	long unlocked = 0, locked = 0;
> +	long unlocked = 0, locked = vpfn_pages(dma, iova, npage);
>  	long i;

The logic in vpfn_pages?() doesn't seem quite right? Don't we want  to
count the number of pages within the range that fall within the rb
tree?

vpfn_pages() looks like it is only counting the number of RB tree
nodes within the range?

Jason

Re: [PATCH 2/4] vfio/type1: batch vfio_find_vpfn() in function vfio_unpin_pages_remote()

Posted by lizhe.67@bytedance.com 7 months, 1 week ago

On Wed, 2 Jul 2025 15:27:59 -0300, jgg@ziepe.ca wrote:

> On Mon, Jun 30, 2025 at 03:25:16PM +0800, lizhe.67@bytedance.com wrote:
> > From: Li Zhe <lizhe.67@bytedance.com>
> > 
> > The function vpfn_pages() can help us determine the number of vpfn
> > nodes on the vpfn rb tree within a specified range. This allows us
> > to avoid searching for each vpfn individually in the function
> > vfio_unpin_pages_remote(). This patch batches the vfio_find_vpfn()
> > calls in function vfio_unpin_pages_remote().
> > 
> > Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
> > ---
> >  drivers/vfio/vfio_iommu_type1.c | 10 +++-------
> >  1 file changed, 3 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> > index a2d7abd4f2c2..330fff4fe96d 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -804,16 +804,12 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
> >  				    unsigned long pfn, unsigned long npage,
> >  				    bool do_accounting)
> >  {
> > -	long unlocked = 0, locked = 0;
> > +	long unlocked = 0, locked = vpfn_pages(dma, iova, npage);
> >  	long i;
> 
> The logic in vpfn_pages?() doesn't seem quite right? Don't we want  to
> count the number of pages within the range that fall within the rb
> tree?
> 
> vpfn_pages() looks like it is only counting the number of RB tree
> nodes within the range?

As I understand it, a vfio_pfn corresponds to a single page, am I right?

Thanks,
Zhe

Re: [PATCH 2/4] vfio/type1: batch vfio_find_vpfn() in function vfio_unpin_pages_remote()

Posted by Jason Gunthorpe 7 months, 1 week ago

On Thu, Jul 03, 2025 at 12:18:22PM +0800, lizhe.67@bytedance.com wrote:
> On Wed, 2 Jul 2025 15:27:59 -0300, jgg@ziepe.ca wrote:
> 
> > On Mon, Jun 30, 2025 at 03:25:16PM +0800, lizhe.67@bytedance.com wrote:
> > > From: Li Zhe <lizhe.67@bytedance.com>
> > > 
> > > The function vpfn_pages() can help us determine the number of vpfn
> > > nodes on the vpfn rb tree within a specified range. This allows us
> > > to avoid searching for each vpfn individually in the function
> > > vfio_unpin_pages_remote(). This patch batches the vfio_find_vpfn()
> > > calls in function vfio_unpin_pages_remote().
> > > 
> > > Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
> > > ---
> > >  drivers/vfio/vfio_iommu_type1.c | 10 +++-------
> > >  1 file changed, 3 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> > > index a2d7abd4f2c2..330fff4fe96d 100644
> > > --- a/drivers/vfio/vfio_iommu_type1.c
> > > +++ b/drivers/vfio/vfio_iommu_type1.c
> > > @@ -804,16 +804,12 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
> > >  				    unsigned long pfn, unsigned long npage,
> > >  				    bool do_accounting)
> > >  {
> > > -	long unlocked = 0, locked = 0;
> > > +	long unlocked = 0, locked = vpfn_pages(dma, iova, npage);
> > >  	long i;
> > 
> > The logic in vpfn_pages?() doesn't seem quite right? Don't we want  to
> > count the number of pages within the range that fall within the rb
> > tree?
> > 
> > vpfn_pages() looks like it is only counting the number of RB tree
> > nodes within the range?
> 
> As I understand it, a vfio_pfn corresponds to a single page, am I right?

It does look that way, it is not what I was expecting iommufd holds
ranges for this job..

So this is OK then

Jason

Re: [PATCH 2/4] vfio/type1: batch vfio_find_vpfn() in function vfio_unpin_pages_remote()

Posted by lizhe.67@bytedance.com 7 months, 1 week ago

On Thu, 3 Jul 2025 09:27:56 -0300, jgg@nvidia.com wrote:

> On Thu, Jul 03, 2025 at 12:18:22PM +0800, lizhe.67@bytedance.com wrote:
> > On Wed, 2 Jul 2025 15:27:59 -0300, jgg@ziepe.ca wrote:
> > 
> > > On Mon, Jun 30, 2025 at 03:25:16PM +0800, lizhe.67@bytedance.com wrote:
> > > > From: Li Zhe <lizhe.67@bytedance.com>
> > > > 
> > > > The function vpfn_pages() can help us determine the number of vpfn
> > > > nodes on the vpfn rb tree within a specified range. This allows us
> > > > to avoid searching for each vpfn individually in the function
> > > > vfio_unpin_pages_remote(). This patch batches the vfio_find_vpfn()
> > > > calls in function vfio_unpin_pages_remote().
> > > > 
> > > > Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
> > > > ---
> > > >  drivers/vfio/vfio_iommu_type1.c | 10 +++-------
> > > >  1 file changed, 3 insertions(+), 7 deletions(-)
> > > > 
> > > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> > > > index a2d7abd4f2c2..330fff4fe96d 100644
> > > > --- a/drivers/vfio/vfio_iommu_type1.c
> > > > +++ b/drivers/vfio/vfio_iommu_type1.c
> > > > @@ -804,16 +804,12 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
> > > >  				    unsigned long pfn, unsigned long npage,
> > > >  				    bool do_accounting)
> > > >  {
> > > > -	long unlocked = 0, locked = 0;
> > > > +	long unlocked = 0, locked = vpfn_pages(dma, iova, npage);
> > > >  	long i;
> > > 
> > > The logic in vpfn_pages?() doesn't seem quite right? Don't we want  to
> > > count the number of pages within the range that fall within the rb
> > > tree?
> > > 
> > > vpfn_pages() looks like it is only counting the number of RB tree
> > > nodes within the range?
> > 
> > As I understand it, a vfio_pfn corresponds to a single page, am I right?
> 
> It does look that way, it is not what I was expecting iommufd holds
> ranges for this job..
> 
> So this is OK then

Thank you. It seems that we have reached a consensus on all the comments.
I will send out a v2 patchset soon.

Thanks,
Zhe