[PATCH] hw/i386/isapc: Remove dead Xen code

[PATCH] hw/i386/isapc: Remove dead Xen code

[Philippe Mathieu-Daudé]

We don't use Xen on the isapc machine: let's remove
pointless code.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/i386/isapc.c | 27 ++++-----------------------
 1 file changed, 4 insertions(+), 23 deletions(-)

diff --git a/hw/i386/isapc.c b/hw/i386/isapc.c
index 1ba9ae22cc3..1e13a30c505 100644
--- a/hw/i386/isapc.c
+++ b/hw/i386/isapc.c
@@ -17,8 +17,6 @@
 #include "hw/ide/ide-bus.h"
 #include "system/kvm.h"
 #include "hw/i386/kvm/clock.h"
-#include "hw/xen/xen-x86.h"
-#include "system/xen.h"
 #include "hw/rtc/mc146818rtc.h"
 #include "target/i386/cpu.h"
 
@@ -37,7 +35,6 @@ static void pc_init_isa(MachineState *machine)
     ISABus *isa_bus;
     uint32_t irq;
     GSIState *gsi_state;
-    MemoryRegion *ram_memory;
     DriveInfo *hd[MAX_IDE_BUS * MAX_IDE_DEVS];
     int i;
 
@@ -77,15 +74,9 @@ static void pc_init_isa(MachineState *machine)
     /*
      * There is no RAM split for the isapc machine
      */
-    if (xen_enabled()) {
-        xen_hvm_init_pc(pcms, &ram_memory);
-    } else {
-        ram_memory = machine->ram;
-
-        pcms->max_ram_below_4g = 3.5 * GiB;
-        x86ms->above_4g_mem_size = 0;
-        x86ms->below_4g_mem_size = machine->ram_size;
-    }
+    pcms->max_ram_below_4g = 3.5 * GiB;
+    x86ms->above_4g_mem_size = 0;
+    x86ms->below_4g_mem_size = machine->ram_size;
 
     x86_cpus_init(x86ms, pcmc->default_cpu_version);
 
@@ -94,17 +85,7 @@ static void pc_init_isa(MachineState *machine)
     }
 
     /* allocate ram and load rom/bios */
-    if (!xen_enabled()) {
-        pc_memory_init(pcms, system_memory, system_memory, 0);
-    } else {
-        assert(machine->ram_size == x86ms->below_4g_mem_size +
-                                    x86ms->above_4g_mem_size);
-
-        if (machine->kernel_filename != NULL) {
-            /* For xen HVM direct kernel boot, load linux here */
-            xen_load_linux(pcms);
-        }
-    }
+    pc_memory_init(pcms, system_memory, system_memory, 0);
 
     gsi_state = pc_gsi_create(&x86ms->gsi, false);
 
-- 
2.51.0

Re: [PATCH] hw/i386/isapc: Remove dead Xen code

[Daniel P. Berrangé]

On Sun, Nov 23, 2025 at 07:58:32PM +0100, Philippe Mathieu-Daudé wrote:
> We don't use Xen on the isapc machine: let's remove
> pointless code.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  hw/i386/isapc.c | 27 ++++-----------------------
>  1 file changed, 4 insertions(+), 23 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
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Re: [PATCH] hw/i386/isapc: Remove dead Xen code

[Mark Cave-Ayland]

On 23/11/2025 18:58, Philippe Mathieu-Daudé wrote:

> We don't use Xen on the isapc machine: let's remove
> pointless code.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   hw/i386/isapc.c | 27 ++++-----------------------
>   1 file changed, 4 insertions(+), 23 deletions(-)
> 
> diff --git a/hw/i386/isapc.c b/hw/i386/isapc.c
> index 1ba9ae22cc3..1e13a30c505 100644
> --- a/hw/i386/isapc.c
> +++ b/hw/i386/isapc.c
> @@ -17,8 +17,6 @@
>   #include "hw/ide/ide-bus.h"
>   #include "system/kvm.h"
>   #include "hw/i386/kvm/clock.h"
> -#include "hw/xen/xen-x86.h"
> -#include "system/xen.h"
>   #include "hw/rtc/mc146818rtc.h"
>   #include "target/i386/cpu.h"
>   
> @@ -37,7 +35,6 @@ static void pc_init_isa(MachineState *machine)
>       ISABus *isa_bus;
>       uint32_t irq;
>       GSIState *gsi_state;
> -    MemoryRegion *ram_memory;
>       DriveInfo *hd[MAX_IDE_BUS * MAX_IDE_DEVS];
>       int i;
>   
> @@ -77,15 +74,9 @@ static void pc_init_isa(MachineState *machine)
>       /*
>        * There is no RAM split for the isapc machine
>        */
> -    if (xen_enabled()) {
> -        xen_hvm_init_pc(pcms, &ram_memory);
> -    } else {
> -        ram_memory = machine->ram;
> -
> -        pcms->max_ram_below_4g = 3.5 * GiB;
> -        x86ms->above_4g_mem_size = 0;
> -        x86ms->below_4g_mem_size = machine->ram_size;
> -    }
> +    pcms->max_ram_below_4g = 3.5 * GiB;
> +    x86ms->above_4g_mem_size = 0;
> +    x86ms->below_4g_mem_size = machine->ram_size;
>   
>       x86_cpus_init(x86ms, pcmc->default_cpu_version);
>   
> @@ -94,17 +85,7 @@ static void pc_init_isa(MachineState *machine)
>       }
>   
>       /* allocate ram and load rom/bios */
> -    if (!xen_enabled()) {
> -        pc_memory_init(pcms, system_memory, system_memory, 0);
> -    } else {
> -        assert(machine->ram_size == x86ms->below_4g_mem_size +
> -                                    x86ms->above_4g_mem_size);
> -
> -        if (machine->kernel_filename != NULL) {
> -            /* For xen HVM direct kernel boot, load linux here */
> -            xen_load_linux(pcms);
> -        }
> -    }
> +    pc_memory_init(pcms, system_memory, system_memory, 0);
>   
>       gsi_state = pc_gsi_create(&x86ms->gsi, false);

FWIW I did contact upstream about this (see 
https://patchew.org/QEMU/20250618112828.235087-1-mark.caveayland@nutanix.com/20250618112828.235087-13-mark.caveayland@nutanix.com/#91b96b24-af60-4a89-91ec-d0e660a76a0a@nutanix.com) 
and they mentioned that it should work, which is why I left it in.

Unfortunately I don't currently have any way to test it here :/


ATB,

Mark.

Re: [PATCH] hw/i386/isapc: Remove dead Xen code

[Alex Bennée]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> We don't use Xen on the isapc machine: let's remove
> pointless code.

Are you sure about this? The older Xen config did support:

  isa
      Simulate an ISA only system

  isa (Default=0; Value='no|yes') 

I don't know why anyone would want a ISA capable HVM machine these days
but I would at least want to know when Xen dropped this as an option in
the commit message.

>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  hw/i386/isapc.c | 27 ++++-----------------------
>  1 file changed, 4 insertions(+), 23 deletions(-)
>
> diff --git a/hw/i386/isapc.c b/hw/i386/isapc.c
> index 1ba9ae22cc3..1e13a30c505 100644
> --- a/hw/i386/isapc.c
> +++ b/hw/i386/isapc.c
> @@ -17,8 +17,6 @@
>  #include "hw/ide/ide-bus.h"
>  #include "system/kvm.h"
>  #include "hw/i386/kvm/clock.h"
> -#include "hw/xen/xen-x86.h"
> -#include "system/xen.h"
>  #include "hw/rtc/mc146818rtc.h"
>  #include "target/i386/cpu.h"
>  
> @@ -37,7 +35,6 @@ static void pc_init_isa(MachineState *machine)
>      ISABus *isa_bus;
>      uint32_t irq;
>      GSIState *gsi_state;
> -    MemoryRegion *ram_memory;
>      DriveInfo *hd[MAX_IDE_BUS * MAX_IDE_DEVS];
>      int i;
>  
> @@ -77,15 +74,9 @@ static void pc_init_isa(MachineState *machine)
>      /*
>       * There is no RAM split for the isapc machine
>       */
> -    if (xen_enabled()) {
> -        xen_hvm_init_pc(pcms, &ram_memory);
> -    } else {
> -        ram_memory = machine->ram;
> -
> -        pcms->max_ram_below_4g = 3.5 * GiB;
> -        x86ms->above_4g_mem_size = 0;
> -        x86ms->below_4g_mem_size = machine->ram_size;
> -    }
> +    pcms->max_ram_below_4g = 3.5 * GiB;
> +    x86ms->above_4g_mem_size = 0;
> +    x86ms->below_4g_mem_size = machine->ram_size;
>  
>      x86_cpus_init(x86ms, pcmc->default_cpu_version);
>  
> @@ -94,17 +85,7 @@ static void pc_init_isa(MachineState *machine)
>      }
>  
>      /* allocate ram and load rom/bios */
> -    if (!xen_enabled()) {
> -        pc_memory_init(pcms, system_memory, system_memory, 0);
> -    } else {
> -        assert(machine->ram_size == x86ms->below_4g_mem_size +
> -                                    x86ms->above_4g_mem_size);
> -
> -        if (machine->kernel_filename != NULL) {
> -            /* For xen HVM direct kernel boot, load linux here */
> -            xen_load_linux(pcms);
> -        }
> -    }
> +    pc_memory_init(pcms, system_memory, system_memory, 0);
>  
>      gsi_state = pc_gsi_create(&x86ms->gsi, false);

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

Re: [PATCH] hw/i386/isapc: Remove dead Xen code

[Philippe Mathieu-Daudé]

On 24/11/25 11:27, Mark Cave-Ayland wrote:
> On 23/11/2025 18:58, Philippe Mathieu-Daudé wrote:
> 
>> We don't use Xen on the isapc machine: let's remove
>> pointless code.
>>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>>   hw/i386/isapc.c | 27 ++++-----------------------
>>   1 file changed, 4 insertions(+), 23 deletions(-)
>>
>> diff --git a/hw/i386/isapc.c b/hw/i386/isapc.c
>> index 1ba9ae22cc3..1e13a30c505 100644
>> --- a/hw/i386/isapc.c
>> +++ b/hw/i386/isapc.c
>> @@ -17,8 +17,6 @@
>>   #include "hw/ide/ide-bus.h"
>>   #include "system/kvm.h"
>>   #include "hw/i386/kvm/clock.h"
>> -#include "hw/xen/xen-x86.h"
>> -#include "system/xen.h"
>>   #include "hw/rtc/mc146818rtc.h"
>>   #include "target/i386/cpu.h"
>> @@ -37,7 +35,6 @@ static void pc_init_isa(MachineState *machine)
>>       ISABus *isa_bus;
>>       uint32_t irq;
>>       GSIState *gsi_state;
>> -    MemoryRegion *ram_memory;
>>       DriveInfo *hd[MAX_IDE_BUS * MAX_IDE_DEVS];
>>       int i;
>> @@ -77,15 +74,9 @@ static void pc_init_isa(MachineState *machine)
>>       /*
>>        * There is no RAM split for the isapc machine
>>        */
>> -    if (xen_enabled()) {
>> -        xen_hvm_init_pc(pcms, &ram_memory);
>> -    } else {
>> -        ram_memory = machine->ram;
>> -
>> -        pcms->max_ram_below_4g = 3.5 * GiB;
>> -        x86ms->above_4g_mem_size = 0;
>> -        x86ms->below_4g_mem_size = machine->ram_size;
>> -    }
>> +    pcms->max_ram_below_4g = 3.5 * GiB;
>> +    x86ms->above_4g_mem_size = 0;
>> +    x86ms->below_4g_mem_size = machine->ram_size;
>>       x86_cpus_init(x86ms, pcmc->default_cpu_version);
>> @@ -94,17 +85,7 @@ static void pc_init_isa(MachineState *machine)
>>       }
>>       /* allocate ram and load rom/bios */
>> -    if (!xen_enabled()) {
>> -        pc_memory_init(pcms, system_memory, system_memory, 0);
>> -    } else {
>> -        assert(machine->ram_size == x86ms->below_4g_mem_size +
>> -                                    x86ms->above_4g_mem_size);
>> -
>> -        if (machine->kernel_filename != NULL) {
>> -            /* For xen HVM direct kernel boot, load linux here */
>> -            xen_load_linux(pcms);
>> -        }
>> -    }
>> +    pc_memory_init(pcms, system_memory, system_memory, 0);
>>       gsi_state = pc_gsi_create(&x86ms->gsi, false);
> 
> FWIW I did contact upstream about this (see https://patchew.org/ 
> QEMU/20250618112828.235087-1- 
> mark.caveayland@nutanix.com/20250618112828.235087-13- 
> mark.caveayland@nutanix.com/#91b96b24-af60-4a89-91ec- 
> d0e660a76a0a@nutanix.com) and they mentioned that it should work, which 
> is why I left it in.
> 
> Unfortunately I don't currently have any way to test it here :/

OK :| IMHO upstream Xen maintainers should provide us a test, otherwise
we can not make our code base evolve.

Re: [PATCH] hw/i386/isapc: Remove dead Xen code

[Alex Bennée]

Philippe Mathieu-Daudé <philmd@linaro.org> writes:

> On 24/11/25 11:27, Mark Cave-Ayland wrote:
>> On 23/11/2025 18:58, Philippe Mathieu-Daudé wrote:
>> 
>>> We don't use Xen on the isapc machine: let's remove
>>> pointless code.
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>>> ---
>>>   hw/i386/isapc.c | 27 ++++-----------------------
>>>   1 file changed, 4 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/hw/i386/isapc.c b/hw/i386/isapc.c
>>> index 1ba9ae22cc3..1e13a30c505 100644
>>> --- a/hw/i386/isapc.c
>>> +++ b/hw/i386/isapc.c
>>> @@ -17,8 +17,6 @@
>>>   #include "hw/ide/ide-bus.h"
>>>   #include "system/kvm.h"
>>>   #include "hw/i386/kvm/clock.h"
>>> -#include "hw/xen/xen-x86.h"
>>> -#include "system/xen.h"
>>>   #include "hw/rtc/mc146818rtc.h"
>>>   #include "target/i386/cpu.h"
>>> @@ -37,7 +35,6 @@ static void pc_init_isa(MachineState *machine)
>>>       ISABus *isa_bus;
>>>       uint32_t irq;
>>>       GSIState *gsi_state;
>>> -    MemoryRegion *ram_memory;
>>>       DriveInfo *hd[MAX_IDE_BUS * MAX_IDE_DEVS];
>>>       int i;
>>> @@ -77,15 +74,9 @@ static void pc_init_isa(MachineState *machine)
>>>       /*
>>>        * There is no RAM split for the isapc machine
>>>        */
>>> -    if (xen_enabled()) {
>>> -        xen_hvm_init_pc(pcms, &ram_memory);
>>> -    } else {
>>> -        ram_memory = machine->ram;
>>> -
>>> -        pcms->max_ram_below_4g = 3.5 * GiB;
>>> -        x86ms->above_4g_mem_size = 0;
>>> -        x86ms->below_4g_mem_size = machine->ram_size;
>>> -    }
>>> +    pcms->max_ram_below_4g = 3.5 * GiB;
>>> +    x86ms->above_4g_mem_size = 0;
>>> +    x86ms->below_4g_mem_size = machine->ram_size;
>>>       x86_cpus_init(x86ms, pcmc->default_cpu_version);
>>> @@ -94,17 +85,7 @@ static void pc_init_isa(MachineState *machine)
>>>       }
>>>       /* allocate ram and load rom/bios */
>>> -    if (!xen_enabled()) {
>>> -        pc_memory_init(pcms, system_memory, system_memory, 0);
>>> -    } else {
>>> -        assert(machine->ram_size == x86ms->below_4g_mem_size +
>>> -                                    x86ms->above_4g_mem_size);
>>> -
>>> -        if (machine->kernel_filename != NULL) {
>>> -            /* For xen HVM direct kernel boot, load linux here */
>>> -            xen_load_linux(pcms);
>>> -        }
>>> -    }
>>> +    pc_memory_init(pcms, system_memory, system_memory, 0);
>>>       gsi_state = pc_gsi_create(&x86ms->gsi, false);
>> FWIW I did contact upstream about this (see https://patchew.org/
>> QEMU/20250618112828.235087-1-
>> mark.caveayland@nutanix.com/20250618112828.235087-13-
>> mark.caveayland@nutanix.com/#91b96b24-af60-4a89-91ec-
>> d0e660a76a0a@nutanix.com) and they mentioned that it should work,
>> which is why I left it in.
>> Unfortunately I don't currently have any way to test it here :/
>
> OK :| IMHO upstream Xen maintainers should provide us a test, otherwise
> we can not make our code base evolve.

Ok how about this:

  As of the xen commit 9e8672f1c36 (tools: remove xend and associated
  python modules) there is no longer the ability to emulate an ISA only
  system. As a result we can drop the code in isapc. We still need to
  support the ISA bus for the -m pc type as Xen doesn't support the q35
  machine model for HVM.

I think the actual support got removed earlier but this was when the
last bits of "Simulate an ISA only system" where removed in 2013.

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro