[PATCH 2/2] xen: Kconfig: nest Xen guest options

Jason Andryuk posted 2 patches 1 month, 1 week ago

[PATCH 2/2] xen: Kconfig: nest Xen guest options

Posted by Jason Andryuk 1 month, 1 week ago
Moving XEN_512GB allows it to nest under XEN_PV.  That also allows
XEN_PVH to nest under XEN as a sibling to XEN_PV and XEN_PVHVM giving:

[*]   Xen guest support
[*]     Xen PV guest support
[*]       Limit Xen pv-domain memory to 512GB
[*]       Xen PV Dom0 support
[*]     Xen PVHVM guest support
[*]     Xen PVH guest support

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
---
 arch/x86/xen/Kconfig | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index b75007eb4ec4..2b105888927c 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -26,6 +26,19 @@ config XEN_PV
 	help
 	  Support running as a Xen PV guest.
 
+config XEN_512GB
+	bool "Limit Xen pv-domain memory to 512GB"
+	depends on XEN_PV && X86_64
+	default y
+	help
+	  Limit paravirtualized user domains to 512GB of RAM.
+
+	  The Xen tools and crash dump analysis tools might not support
+	  pv-domains with more than 512 GB of RAM. This option controls the
+	  default setting of the kernel to use only up to 512 GB or more.
+	  It is always possible to change the default via specifying the
+	  boot parameter "xen_512gb_limit".
+
 config XEN_PV_SMP
 	def_bool y
 	depends on XEN_PV && SMP
@@ -53,19 +66,6 @@ config XEN_PVHVM_GUEST
 	help
 	  Support running as a Xen PVHVM guest.
 
-config XEN_512GB
-	bool "Limit Xen pv-domain memory to 512GB"
-	depends on XEN_PV
-	default y
-	help
-	  Limit paravirtualized user domains to 512GB of RAM.
-
-	  The Xen tools and crash dump analysis tools might not support
-	  pv-domains with more than 512 GB of RAM. This option controls the
-	  default setting of the kernel to use only up to 512 GB or more.
-	  It is always possible to change the default via specifying the
-	  boot parameter "xen_512gb_limit".
-
 config XEN_SAVE_RESTORE
 	bool
 	depends on XEN
-- 
2.26.2


Re: [PATCH 2/2] xen: Kconfig: nest Xen guest options

Posted by boris.ostrovsky@oracle.com 1 month, 1 week ago
On 10/14/20 1:53 PM, Jason Andryuk wrote:
> +config XEN_512GB
> +	bool "Limit Xen pv-domain memory to 512GB"
> +	depends on XEN_PV && X86_64


Why is X86_64 needed here?


-boris




Re: [PATCH 2/2] xen: Kconfig: nest Xen guest options

Posted by Andrew Cooper 1 month, 1 week ago
On 15/10/2020 13:37, boris.ostrovsky@oracle.com wrote:
> On 10/14/20 1:53 PM, Jason Andryuk wrote:
>> +config XEN_512GB
>> +	bool "Limit Xen pv-domain memory to 512GB"
>> +	depends on XEN_PV && X86_64
>
> Why is X86_64 needed here?

>512G support was implemented using a direct-mapped P2M, and is rather
beyond the virtual address capabilities of 32bit.

~Andrew

Re: [PATCH 2/2] xen: Kconfig: nest Xen guest options

Posted by boris.ostrovsky@oracle.com 1 month, 1 week ago
On 10/15/20 9:10 AM, Andrew Cooper wrote:
> On 15/10/2020 13:37, boris.ostrovsky@oracle.com wrote:
>> On 10/14/20 1:53 PM, Jason Andryuk wrote:
>>> +config XEN_512GB
>>> +	bool "Limit Xen pv-domain memory to 512GB"
>>> +	depends on XEN_PV && X86_64
>> Why is X86_64 needed here?
>> 512G support was implemented using a direct-mapped P2M, and is rather
> beyond the virtual address capabilities of 32bit.
>

Yes, my point was that XEN_PV already depends on X86_64.


-boris


Re: [PATCH 2/2] xen: Kconfig: nest Xen guest options

Posted by Jason Andryuk 1 month, 1 week ago
On Thu, Oct 15, 2020 at 9:17 AM <boris.ostrovsky@oracle.com> wrote:
>
>
> On 10/15/20 9:10 AM, Andrew Cooper wrote:
> > On 15/10/2020 13:37, boris.ostrovsky@oracle.com wrote:
> >> On 10/14/20 1:53 PM, Jason Andryuk wrote:
> >>> +config XEN_512GB
> >>> +   bool "Limit Xen pv-domain memory to 512GB"
> >>> +   depends on XEN_PV && X86_64
> >> Why is X86_64 needed here?
> >> 512G support was implemented using a direct-mapped P2M, and is rather
> > beyond the virtual address capabilities of 32bit.
> >
>
> Yes, my point was that XEN_PV already depends on X86_64.

Oh, thanks for catching this.  I re-introduced it by accident when
rebasing the patches.

Regards,
Jason

Re: [PATCH 2/2] xen: Kconfig: nest Xen guest options

Posted by Jürgen Groß 1 month, 1 week ago
On 14.10.20 19:53, Jason Andryuk wrote:
> Moving XEN_512GB allows it to nest under XEN_PV.  That also allows
> XEN_PVH to nest under XEN as a sibling to XEN_PV and XEN_PVHVM giving:
> 
> [*]   Xen guest support
> [*]     Xen PV guest support
> [*]       Limit Xen pv-domain memory to 512GB
> [*]       Xen PV Dom0 support

This has currently a wrong text/semantics:

It should be split to CONFIG_XEN_DOM0 and CONFIG_XEN_PV_DOM0.

Otherwise the backends won't be enabled per default for a PVH-only
config meant to be Dom0-capable.

You don't have to do that in your patches if you don't want to, but
I wanted to mention it with you touching this area of Kconfig.

> [*]     Xen PVHVM guest support
> [*]     Xen PVH guest support
> 
> Signed-off-by: Jason Andryuk <jandryuk@gmail.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

Re: [PATCH 2/2] xen: Kconfig: nest Xen guest options

Posted by Jason Andryuk 1 month, 1 week ago
On Thu, Oct 15, 2020 at 5:42 AM Jürgen Groß <jgross@suse.com> wrote:
>
> On 14.10.20 19:53, Jason Andryuk wrote:
> > Moving XEN_512GB allows it to nest under XEN_PV.  That also allows
> > XEN_PVH to nest under XEN as a sibling to XEN_PV and XEN_PVHVM giving:
> >
> > [*]   Xen guest support
> > [*]     Xen PV guest support
> > [*]       Limit Xen pv-domain memory to 512GB
> > [*]       Xen PV Dom0 support
>
> This has currently a wrong text/semantics:
>
> It should be split to CONFIG_XEN_DOM0 and CONFIG_XEN_PV_DOM0.
>
> Otherwise the backends won't be enabled per default for a PVH-only
> config meant to be Dom0-capable.
>
> You don't have to do that in your patches if you don't want to, but
> I wanted to mention it with you touching this area of Kconfig.

Yes, good point.  I had not considered that.

> > [*]     Xen PVHVM guest support
> > [*]     Xen PVH guest support
> >
> > Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
>
> Reviewed-by: Juergen Gross <jgross@suse.com>

Thanks,
Jason