Xen devel - Apr 2010 - [PATCH 5 of 6] unplug emulated devices

Hi all,
this patch adds a xen_unplug command line option to the kernel to unplug
xen emulated devices.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

---
 arch/x86/xen/enlighten.c |   30 +++++++++++++++++++++++++++++-
 1 files changed, 29 insertions(+), 1 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 2ce2da1..7acb130 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -37,6 +37,7 @@
 #include <xen/interface/memory.h>
 #include <xen/interface/hvm/hvm_op.h>
 #include <xen/interface/hvm/params.h>
+#include <xen/interface/platform_pci.h>
 #include <xen/features.h>
 #include <xen/page.h>
 #include <xen/hvm.h>
@@ -86,6 +87,7 @@ struct shared_info xen_dummy_shared_info;
 void *xen_initial_gdt;
 
 int xen_have_vector_callback;
+int unplug;
 
 /*
  * Point at some empty memory to start with. We map the real shared_info
@@ -1389,9 +1391,35 @@ void __init xen_guest_init(void)
 		x86_platform_ipi_callback = do_hvm_pv_evtchn_intr;
 		xen_have_vector_callback = 1;
 	}
-
+	if (unplug) {
+		/* unplug emulated devices */
+		outw(UNPLUG_ALL, XEN_IOPORT_UNPLUG);
+	}
 	have_vcpu_info_placement = 0;
 	x86_init.irqs.intr_init = xen_init_IRQ;
 	machine_ops = xen_machine_ops;
 }
 
+static int __init parse_unplug(char *arg)
+{
+	char *p, *q;
+
+	for (p = arg; p; p = q) {
+		q = strchr(arg, '','');
+		if (q)
+			*q++ = ''\0'';
+		if (!strcmp(p, "all"))
+			unplug |= UNPLUG_ALL;
+		else if (!strcmp(p, "ide-disks"))
+			unplug |= UNPLUG_ALL_IDE_DISKS;
+		else if (!strcmp(p, "aux-ide-disks"))
+			unplug |= UNPLUG_AUX_IDE_DISKS;
+		else if (!strcmp(p, "nics"))
+			unplug |= UNPLUG_ALL_NICS;
+		else
+			printk(KERN_WARNING "unrecognised option ''%s'' "
+				 "in module parameter ''dev_unplug''\n", p);
+	}
+	return 0;
+}
+early_param("xen_unplug", parse_unplug);
-- 
1.5.4.3


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On Thu, Apr 22, 2010 at 04:16:50PM +0100, Stefano Stabellini
wrote:
> Hi all,
> this patch adds a xen_unplug command line option to the kernel to unplug
> xen emulated devices.
For those folks who don''t understand the pain^H^H^Htransition from
emulated device
to a PV device, can you do a more detailed writeup?

Why don''t we want this be enabled by default? Perhaps you want to make
the parameter only parse the disable option - devices which we _dont_
want to be unplugged. So paramter name would
''xen_keep_plugged=''.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> 
> ---
>  arch/x86/xen/enlighten.c |   30 +++++++++++++++++++++++++++++-
>  1 files changed, 29 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 2ce2da1..7acb130 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -37,6 +37,7 @@
>  #include <xen/interface/memory.h>
>  #include <xen/interface/hvm/hvm_op.h>
>  #include <xen/interface/hvm/params.h>
> +#include <xen/interface/platform_pci.h>
>  #include <xen/features.h>
>  #include <xen/page.h>
>  #include <xen/hvm.h>
> @@ -86,6 +87,7 @@ struct shared_info xen_dummy_shared_info;
>  void *xen_initial_gdt;
>  
>  int xen_have_vector_callback;
> +int unplug;
>  
>  /*
>   * Point at some empty memory to start with. We map the real shared_info
> @@ -1389,9 +1391,35 @@ void __init xen_guest_init(void)
>  		x86_platform_ipi_callback = do_hvm_pv_evtchn_intr;
>  		xen_have_vector_callback = 1;
>  	}
> -
> +	if (unplug) {
> +		/* unplug emulated devices */
> +		outw(UNPLUG_ALL, XEN_IOPORT_UNPLUG);
> +	}
>  	have_vcpu_info_placement = 0;
>  	x86_init.irqs.intr_init = xen_init_IRQ;
>  	machine_ops = xen_machine_ops;
>  }
>  
> +static int __init parse_unplug(char *arg)
> +{
> +	char *p, *q;
> +
> +	for (p = arg; p; p = q) {
> +		q = strchr(arg, '','');
> +		if (q)
> +			*q++ = ''\0'';
> +		if (!strcmp(p, "all"))
> +			unplug |= UNPLUG_ALL;
> +		else if (!strcmp(p, "ide-disks"))
> +			unplug |= UNPLUG_ALL_IDE_DISKS;
> +		else if (!strcmp(p, "aux-ide-disks"))
> +			unplug |= UNPLUG_AUX_IDE_DISKS;
> +		else if (!strcmp(p, "nics"))
> +			unplug |= UNPLUG_ALL_NICS;
> +		else
> +			printk(KERN_WARNING "unrecognised option ''%s''
"
> +				 "in module parameter ''dev_unplug''\n", p);
> +	}
> +	return 0;
> +}
> +early_param("xen_unplug", parse_unplug);
> -- 
> 1.5.4.3
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
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On Thu, 22 Apr 2010, Konrad Rzeszutek Wilk wrote:
> On Thu, Apr 22, 2010 at 04:16:50PM +0100, Stefano Stabellini wrote:
> > Hi all,
> > this patch adds a xen_unplug command line option to the kernel to
unplug
> > xen emulated devices.
> 
> For those folks who don''t understand the pain^H^H^Htransition from
emulated device
> to a PV device, can you do a more detailed writeup?
> 
When the guest loads, if pv drivers are available, the guest is supposed
to unplug the emulated disks and network cards before initializing the pv
drivers.

> Why don''t we want this be enabled by default? Perhaps you want to
make
> the parameter only parse the disable option - devices which we _dont_
> want to be unplugged. So paramter name would
''xen_keep_plugged=''.
If the kernel is configured correctly and pv drivers are present, we
definitely want to unplug the emulated devices, however this might imply
that other command line options to the kernel must be changed as well.

For example if before you had: root=/dev/hda1
with pv drivers you need: root=/dev/xvda1

Besides qemu offers an unplug interface rather than a keep_plugged
interface so it came natural to export an unplug interface as well...

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