[PATCH V2] Xen: ARM: Zero reserved fields of xatp before making hypervisor call

[PATCH V2] Xen: ARM: Zero reserved fields of xatp before making hypervisor call

[Jiandi An]

Ensure all reserved fields of xatp are zero before making
hypervisor call to XEN in xen_map_device_mmio().
xenmem_add_to_physmap_one() in XEN fails the mapping request if
extra.res reserved field in xatp is not zero for XENMAPSPACE_dev_mmio
request.

Signed-off-by: Jiandi An <anjiandi@codeaurora.org>
---
Changed zeroing xatp to a static initialization
of .domid and .space for xatp.

 drivers/xen/arm-device.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/arm-device.c b/drivers/xen/arm-device.c
index 778acf8..85dd20e 100644
--- a/drivers/xen/arm-device.c
+++ b/drivers/xen/arm-device.c
@@ -58,9 +58,13 @@ static int xen_map_device_mmio(const struct resource *resources,
 	xen_pfn_t *gpfns;
 	xen_ulong_t *idxs;
 	int *errs;
-	struct xen_add_to_physmap_range xatp;
 
 	for (i = 0; i < count; i++) {
+		struct xen_add_to_physmap_range xatp = {
+			.domid = DOMID_SELF,
+			.space = XENMAPSPACE_dev_mmio
+		};
+
 		r = &resources[i];
 		nr = DIV_ROUND_UP(resource_size(r), XEN_PAGE_SIZE);
 		if ((resource_type(r) != IORESOURCE_MEM) || (nr == 0))
@@ -87,9 +91,7 @@ static int xen_map_device_mmio(const struct resource *resources,
 			idxs[j] = XEN_PFN_DOWN(r->start) + j;
 		}
 
-		xatp.domid = DOMID_SELF;
 		xatp.size = nr;
-		xatp.space = XENMAPSPACE_dev_mmio;
 
 		set_xen_guest_handle(xatp.gpfns, gpfns);
 		set_xen_guest_handle(xatp.idxs, idxs);
-- 
Jiandi An
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.

Re: [PATCH V2] Xen: ARM: Zero reserved fields of xatp before making hypervisor call

[Juergen Gross]

On 28/12/16 01:47, Jiandi An wrote:
> Ensure all reserved fields of xatp are zero before making
> hypervisor call to XEN in xen_map_device_mmio().
> xenmem_add_to_physmap_one() in XEN fails the mapping request if
> extra.res reserved field in xatp is not zero for XENMAPSPACE_dev_mmio
> request.
> 
> Signed-off-by: Jiandi An <anjiandi@codeaurora.org>
> ---
> Changed zeroing xatp to a static initialization
> of .domid and .space for xatp.
> 
>  drivers/xen/arm-device.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/arm-device.c b/drivers/xen/arm-device.c
> index 778acf8..85dd20e 100644
> --- a/drivers/xen/arm-device.c
> +++ b/drivers/xen/arm-device.c
> @@ -58,9 +58,13 @@ static int xen_map_device_mmio(const struct resource *resources,
>  	xen_pfn_t *gpfns;
>  	xen_ulong_t *idxs;
>  	int *errs;
> -	struct xen_add_to_physmap_range xatp;
>  
>  	for (i = 0; i < count; i++) {
> +		struct xen_add_to_physmap_range xatp = {
> +			.domid = DOMID_SELF,
> +			.space = XENMAPSPACE_dev_mmio
> +		};
> +

I still don't see the need to re-initialize the input parts of xatp
on each loop iteration unless you can show the need for it (e.g. a
buggy hypervisor version not conforming to the interface specification).

OTOH I don't feel really strong about it and let Stefano being the
maintainer for the ARM parts decide.


Juergen

>  		r = &resources[i];
>  		nr = DIV_ROUND_UP(resource_size(r), XEN_PAGE_SIZE);
>  		if ((resource_type(r) != IORESOURCE_MEM) || (nr == 0))
> @@ -87,9 +91,7 @@ static int xen_map_device_mmio(const struct resource *resources,
>  			idxs[j] = XEN_PFN_DOWN(r->start) + j;
>  		}
>  
> -		xatp.domid = DOMID_SELF;
>  		xatp.size = nr;
> -		xatp.space = XENMAPSPACE_dev_mmio;
>  
>  		set_xen_guest_handle(xatp.gpfns, gpfns);
>  		set_xen_guest_handle(xatp.idxs, idxs);
> 

Re: [PATCH V2] Xen: ARM: Zero reserved fields of xatp before making hypervisor call

[Stefano Stabellini]

On Mon, 2 Jan 2017, Juergen Gross wrote:
> On 28/12/16 01:47, Jiandi An wrote:
> > Ensure all reserved fields of xatp are zero before making
> > hypervisor call to XEN in xen_map_device_mmio().
> > xenmem_add_to_physmap_one() in XEN fails the mapping request if
> > extra.res reserved field in xatp is not zero for XENMAPSPACE_dev_mmio
> > request.
> > 
> > Signed-off-by: Jiandi An <anjiandi@codeaurora.org>
> > ---
> > Changed zeroing xatp to a static initialization
> > of .domid and .space for xatp.
> > 
> >  drivers/xen/arm-device.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/xen/arm-device.c b/drivers/xen/arm-device.c
> > index 778acf8..85dd20e 100644
> > --- a/drivers/xen/arm-device.c
> > +++ b/drivers/xen/arm-device.c
> > @@ -58,9 +58,13 @@ static int xen_map_device_mmio(const struct resource *resources,
> >  	xen_pfn_t *gpfns;
> >  	xen_ulong_t *idxs;
> >  	int *errs;
> > -	struct xen_add_to_physmap_range xatp;
> >  
> >  	for (i = 0; i < count; i++) {
> > +		struct xen_add_to_physmap_range xatp = {
> > +			.domid = DOMID_SELF,
> > +			.space = XENMAPSPACE_dev_mmio
> > +		};
> > +
> 
> I still don't see the need to re-initialize the input parts of xatp
> on each loop iteration unless you can show the need for it (e.g. a
> buggy hypervisor version not conforming to the interface specification).
> 
> OTOH I don't feel really strong about it and let Stefano being the
> maintainer for the ARM parts decide.

I don't feel strongly about this either - I think this patch is good
enough. I'll apply to xentip.

Re: [PATCH V2] Xen: ARM: Zero reserved fields of xatp before making hypervisor call

[Julien Grall]

Hi Stefano,

On 03/01/17 18:03, Stefano Stabellini wrote:
> On Mon, 2 Jan 2017, Juergen Gross wrote:
>> On 28/12/16 01:47, Jiandi An wrote:
>>> Ensure all reserved fields of xatp are zero before making
>>> hypervisor call to XEN in xen_map_device_mmio().
>>> xenmem_add_to_physmap_one() in XEN fails the mapping request if
>>> extra.res reserved field in xatp is not zero for XENMAPSPACE_dev_mmio
>>> request.
>>>
>>> Signed-off-by: Jiandi An <anjiandi@codeaurora.org>
>>> ---
>>> Changed zeroing xatp to a static initialization
>>> of .domid and .space for xatp.
>>>
>>>  drivers/xen/arm-device.c | 8 +++++---
>>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/xen/arm-device.c b/drivers/xen/arm-device.c
>>> index 778acf8..85dd20e 100644
>>> --- a/drivers/xen/arm-device.c
>>> +++ b/drivers/xen/arm-device.c
>>> @@ -58,9 +58,13 @@ static int xen_map_device_mmio(const struct resource *resources,
>>>  	xen_pfn_t *gpfns;
>>>  	xen_ulong_t *idxs;
>>>  	int *errs;
>>> -	struct xen_add_to_physmap_range xatp;
>>>
>>>  	for (i = 0; i < count; i++) {
>>> +		struct xen_add_to_physmap_range xatp = {
>>> +			.domid = DOMID_SELF,
>>> +			.space = XENMAPSPACE_dev_mmio
>>> +		};
>>> +
>>
>> I still don't see the need to re-initialize the input parts of xatp
>> on each loop iteration unless you can show the need for it (e.g. a
>> buggy hypervisor version not conforming to the interface specification).
>>
>> OTOH I don't feel really strong about it and let Stefano being the
>> maintainer for the ARM parts decide.
>
> I don't feel strongly about this either - I think this patch is good
> enough. I'll apply to xentip.

I think this patch should be backported to stable trees because the 
issue could appear depending on the compiler.

Cheers,

-- 
Julien Grall