[Qemu-devel] [PATCH] exec: Limit translation limiting in address_space_translate to xen

[Qemu-devel] [PATCH] exec: Limit translation limiting in address_space_translate to xen

[Alexey Kardashevskiy]

The address_space_translate() function cuts the returned plen (page size)
to hardcoded TARGET_PAGE_SIZE. This function can be used on pages bigger
than that so this limiting should not be used on such pages.

Since originally the limiting was introduced for XEN, we can safely
limit this piece of code to XEN. So does the patch.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---

I need this change for VFIO-on-sPAPR series as it is going to support
16MB IOMMU pages. Thanks.
---
 exec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/exec.c b/exec.c
index 91513c6..cf12049 100644
--- a/exec.c
+++ b/exec.c
@@ -380,7 +380,7 @@ MemoryRegion *address_space_translate(AddressSpace *as, hwaddr addr,
         as = iotlb.target_as;
     }
 
-    if (memory_access_is_direct(mr, is_write)) {
+    if (xen_enabled() && memory_access_is_direct(mr, is_write)) {
         hwaddr page = ((addr & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE) - addr;
         len = MIN(page, len);
     }
-- 
1.8.4.rc4

Re: [Qemu-devel] [PATCH] exec: Limit translation limiting in address_space_translate to xen

[Paolo Bonzini]

Il 27/03/2014 05:35, Alexey Kardashevskiy ha scritto:
> The address_space_translate() function cuts the returned plen (page size)
> to hardcoded TARGET_PAGE_SIZE. This function can be used on pages bigger
> than that so this limiting should not be used on such pages.
>
> Since originally the limiting was introduced for XEN, we can safely
> limit this piece of code to XEN. So does the patch.
>
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
>
> I need this change for VFIO-on-sPAPR series as it is going to support
> 16MB IOMMU pages. Thanks.
> ---
>  exec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/exec.c b/exec.c
> index 91513c6..cf12049 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -380,7 +380,7 @@ MemoryRegion *address_space_translate(AddressSpace *as, hwaddr addr,
>          as = iotlb.target_as;
>      }
>
> -    if (memory_access_is_direct(mr, is_write)) {
> +    if (xen_enabled() && memory_access_is_direct(mr, is_write)) {
>          hwaddr page = ((addr & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE) - addr;
>          len = MIN(page, len);
>      }
>

Stefano, can you include this in your Xen tree for 2.1?

Paolo

Re: [Qemu-devel] [PATCH] exec: Limit translation limiting in address_space_translate to xen

[Stefano Stabellini]

On Thu, 27 Mar 2014, Paolo Bonzini wrote:
> Il 27/03/2014 05:35, Alexey Kardashevskiy ha scritto:
> > The address_space_translate() function cuts the returned plen (page size)
> > to hardcoded TARGET_PAGE_SIZE. This function can be used on pages bigger
> > than that so this limiting should not be used on such pages.
> > 
> > Since originally the limiting was introduced for XEN, we can safely
> > limit this piece of code to XEN. So does the patch.
> > 
> > Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > ---
> > 
> > I need this change for VFIO-on-sPAPR series as it is going to support
> > 16MB IOMMU pages. Thanks.
> > ---
> >  exec.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/exec.c b/exec.c
> > index 91513c6..cf12049 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -380,7 +380,7 @@ MemoryRegion *address_space_translate(AddressSpace *as,
> > hwaddr addr,
> >          as = iotlb.target_as;
> >      }
> > 
> > -    if (memory_access_is_direct(mr, is_write)) {
> > +    if (xen_enabled() && memory_access_is_direct(mr, is_write)) {
> >          hwaddr page = ((addr & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE) -
> > addr;
> >          len = MIN(page, len);
> >      }
> > 
> 
> Stefano, can you include this in your Xen tree for 2.1?

Sure.