Re: [Xen-devel] [RFC XEN PATCH v3 01/39] x86_64/mm: fix the PDX group check in mem_hotadd_check()

2017-10-27 Thread Haozhong Zhang 
On 10/27/17 14:49 +0800, Chao Peng wrote:
> On Mon, 2017-09-11 at 12:37 +0800, Haozhong Zhang wrote:
> > The current check refuses the hot-plugged memory that falls in one
> > unused PDX group, which should be allowed.
> 
> Looks reasonable to me. The only thing I can think of is you can double
> check if the following find_next_zero_bit/find_next_bit will still
> work. 

The first check in mem_hotadd_check() ensures spfn < epfn, so sidx <=
eidx here. Compared with the previous code, the only added case is
sidx == eidx, which is what this patch intends to allow and tested.

Haozhong

> 
> Chao
> > 
> > Signed-off-by: Haozhong Zhang 
> > ---
> > Cc: Jan Beulich 
> > Cc: Andrew Cooper 
> > ---
> >  xen/arch/x86/x86_64/mm.c | 6 +-
> >  1 file changed, 1 insertion(+), 5 deletions(-)
> > 
> > diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
> > index 11746730b4..6c5221f90c 100644
> > --- a/xen/arch/x86/x86_64/mm.c
> > +++ b/xen/arch/x86/x86_64/mm.c
> > @@ -1296,12 +1296,8 @@ static int mem_hotadd_check(unsigned long spfn,
> > unsigned long epfn)
> >  return 0;
> >  
> >  /* Make sure the new range is not present now */
> > -sidx = ((pfn_to_pdx(spfn) + PDX_GROUP_COUNT - 1)  &
> > ~(PDX_GROUP_COUNT - 1))
> > -/ PDX_GROUP_COUNT;
> > +sidx = (pfn_to_pdx(spfn) & ~(PDX_GROUP_COUNT - 1)) /
> > PDX_GROUP_COUNT;
> >  eidx = (pfn_to_pdx(epfn - 1) & ~(PDX_GROUP_COUNT - 1)) /
> > PDX_GROUP_COUNT;
> > -if (sidx >= eidx)
> > -return 0;
> > -
> >  s = find_next_zero_bit(pdx_group_valid, eidx, sidx);
> >  if ( s > eidx )
> >  return 0;

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [RFC XEN PATCH v3 01/39] x86_64/mm: fix the PDX group check in mem_hotadd_check()

2017-10-27 Thread Chao Peng 
On Mon, 2017-09-11 at 12:37 +0800, Haozhong Zhang wrote:
> The current check refuses the hot-plugged memory that falls in one
> unused PDX group, which should be allowed.

Looks reasonable to me. The only thing I can think of is you can double
check if the following find_next_zero_bit/find_next_bit will still
work. 

Chao
> 
> Signed-off-by: Haozhong Zhang 
> ---
> Cc: Jan Beulich 
> Cc: Andrew Cooper 
> ---
>  xen/arch/x86/x86_64/mm.c | 6 +-
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
> index 11746730b4..6c5221f90c 100644
> --- a/xen/arch/x86/x86_64/mm.c
> +++ b/xen/arch/x86/x86_64/mm.c
> @@ -1296,12 +1296,8 @@ static int mem_hotadd_check(unsigned long spfn,
> unsigned long epfn)
>  return 0;
>  
>  /* Make sure the new range is not present now */
> -sidx = ((pfn_to_pdx(spfn) + PDX_GROUP_COUNT - 1)  &
> ~(PDX_GROUP_COUNT - 1))
> -/ PDX_GROUP_COUNT;
> +sidx = (pfn_to_pdx(spfn) & ~(PDX_GROUP_COUNT - 1)) /
> PDX_GROUP_COUNT;
>  eidx = (pfn_to_pdx(epfn - 1) & ~(PDX_GROUP_COUNT - 1)) /
> PDX_GROUP_COUNT;
> -if (sidx >= eidx)
> -return 0;
> -
>  s = find_next_zero_bit(pdx_group_valid, eidx, sidx);
>  if ( s > eidx )
>  return 0;

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

[Xen-devel] [RFC XEN PATCH v3 01/39] x86_64/mm: fix the PDX group check in mem_hotadd_check()

2017-09-10 Thread Haozhong Zhang 
The current check refuses the hot-plugged memory that falls in one
unused PDX group, which should be allowed.

Signed-off-by: Haozhong Zhang 
---
Cc: Jan Beulich 
Cc: Andrew Cooper 
---
 xen/arch/x86/x86_64/mm.c | 6 +-
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 11746730b4..6c5221f90c 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -1296,12 +1296,8 @@ static int mem_hotadd_check(unsigned long spfn, unsigned 
long epfn)
 return 0;
 
 /* Make sure the new range is not present now */
-sidx = ((pfn_to_pdx(spfn) + PDX_GROUP_COUNT - 1)  & ~(PDX_GROUP_COUNT - 1))
-/ PDX_GROUP_COUNT;
+sidx = (pfn_to_pdx(spfn) & ~(PDX_GROUP_COUNT - 1)) / PDX_GROUP_COUNT;
 eidx = (pfn_to_pdx(epfn - 1) & ~(PDX_GROUP_COUNT - 1)) / PDX_GROUP_COUNT;
-if (sidx >= eidx)
-return 0;
-
 s = find_next_zero_bit(pdx_group_valid, eidx, sidx);
 if ( s > eidx )
 return 0;
-- 
2.14.1


___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel