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From: "Philippe Mathieu-Daudé" <philmd@redhat.com>
To: Cornelia Huck <cohuck@redhat.com>,
	David Gibson <david@gibson.dropbear.id.au>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, "Aurelien Jarno" <aurelien@aurel32.net>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"Anthony Perard" <anthony.perard@citrix.com>,
	qemu-ppc@nongnu.org, qemu-s390x@nongnu.org,
	"Halil Pasic" <pasic@linux.ibm.com>,
	"Huacai Chen" <chenhuacai@kernel.org>,
	xen-devel@lists.xenproject.org,
	"Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>,
	qemu-arm@nongnu.org,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	kvm@vger.kernel.org, "BALATON Zoltan" <balaton@eik.bme.hu>,
	"Leif Lindholm" <leif@nuviainc.com>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	"Radoslaw Biernacki" <rad@semihalf.com>,
	"Alistair Francis" <alistair@alistair23.me>,
	"Paul Durrant" <paul@xen.org>,
	"Eduardo Habkost" <ehabkost@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Thomas Huth" <thuth@redhat.com>,
	"Jiaxun Yang" <jiaxun.yang@flygoat.com>,
	"Hervé Poussineau" <hpoussin@reactos.org>,
	"Greg Kurz" <groug@kaod.org>,
	"Christian Borntraeger" <borntraeger@de.ibm.com>,
	"Edgar E. Iglesias" <edgar.iglesias@gmail.com>,
	"David Hildenbrand" <david@redhat.com>,
	"Mark Cave-Ayland" <mark.cave-ayland@ilande.co.uk>,
	"Aleksandar Rikalo" <aleksandar.rikalo@syrmia.com>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>
Subject: Re: [PATCH v2 01/11] accel/kvm: Check MachineClass kvm_type() return value
Date: Tue, 23 Feb 2021 12:23:46 +0100	[thread overview]
Message-ID: <98ed9478-240d-cd20-ac84-82c540bd3e21@redhat.com> (raw)
In-Reply-To: <20210223113634.6626c8f8.cohuck@redhat.com>

On 2/23/21 11:36 AM, Cornelia Huck wrote:
> On Tue, 23 Feb 2021 10:37:01 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
>> On Tue, Feb 23, 2021 at 10:33:55AM +1100, David Gibson wrote:
>>> On Mon, Feb 22, 2021 at 06:50:44PM +0100, Cornelia Huck wrote:  
>>>> On Mon, 22 Feb 2021 18:41:07 +0100
>>>> Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>>>>   
>>>>> On 2/22/21 6:24 PM, Cornelia Huck wrote:  
>>>>>> On Fri, 19 Feb 2021 18:38:37 +0100
>>>>>> Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>>>>>>     
>>>>>>> MachineClass::kvm_type() can return -1 on failure.
>>>>>>> Document it, and add a check in kvm_init().
>>>>>>>
>>>>>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>>>>>> ---
>>>>>>>  include/hw/boards.h | 3 ++-
>>>>>>>  accel/kvm/kvm-all.c | 6 ++++++
>>>>>>>  2 files changed, 8 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/include/hw/boards.h b/include/hw/boards.h
>>>>>>> index a46dfe5d1a6..68d3d10f6b0 100644
>>>>>>> --- a/include/hw/boards.h
>>>>>>> +++ b/include/hw/boards.h
>>>>>>> @@ -127,7 +127,8 @@ typedef struct {
>>>>>>>   *    implement and a stub device is required.
>>>>>>>   * @kvm_type:
>>>>>>>   *    Return the type of KVM corresponding to the kvm-type string option or
>>>>>>> - *    computed based on other criteria such as the host kernel capabilities.
>>>>>>> + *    computed based on other criteria such as the host kernel capabilities
>>>>>>> + *    (which can't be negative), or -1 on error.
>>>>>>>   * @numa_mem_supported:
>>>>>>>   *    true if '--numa node.mem' option is supported and false otherwise
>>>>>>>   * @smp_parse:
>>>>>>> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
>>>>>>> index 84c943fcdb2..b069938d881 100644
>>>>>>> --- a/accel/kvm/kvm-all.c
>>>>>>> +++ b/accel/kvm/kvm-all.c
>>>>>>> @@ -2057,6 +2057,12 @@ static int kvm_init(MachineState *ms)
>>>>>>>                                                              "kvm-type",
>>>>>>>                                                              &error_abort);
>>>>>>>          type = mc->kvm_type(ms, kvm_type);
>>>>>>> +        if (type < 0) {
>>>>>>> +            ret = -EINVAL;
>>>>>>> +            fprintf(stderr, "Failed to detect kvm-type for machine '%s'\n",
>>>>>>> +                    mc->name);
>>>>>>> +            goto err;
>>>>>>> +        }
>>>>>>>      }
>>>>>>>  
>>>>>>>      do {    
>>>>>>
>>>>>> No objection to this patch; but I'm wondering why some non-pseries
>>>>>> machines implement the kvm_type callback, when I see the kvm-type
>>>>>> property only for pseries? Am I holding my git grep wrong?    
>>>>>
>>>>> Can it be what David commented here?
>>>>> https://www.mail-archive.com/qemu-devel@nongnu.org/msg784508.html
>>>>>   
>>>>
>>>> Ok, I might be confused about the other ppc machines; but I'm wondering
>>>> about the kvm_type callback for mips and arm/virt. Maybe I'm just
>>>> confused by the whole mechanism?  
>>>
>>> For ppc at least, not sure about in general, pseries is the only
>>> machine type that can possibly work under more than one KVM flavour
>>> (HV or PR).  So, it's the only one where it's actually useful to be
>>> able to configure this.  
>>
>> Wait... I'm not sure that's true.  At least theoretically, some of the
>> Book3E platforms could work with either PR or the Book3E specific
>> KVM.  Not sure if KVM PR supports all the BookE instructions it would
>> need to in practice.
>>
>> Possibly pseries is just the platform where there's been enough people
>> interested in setting the KVM flavour so far.
> 
> If I'm not utterly confused by the code, it seems the pseries machines
> are the only ones where you can actually get to an invocation of
> ->kvm_type(): You need to have a 'kvm-type' machine property, and
> AFAICS only the pseries machine has that.

OMG you are right... This changed in commit f2ce39b4f06
("vl: make qemu_get_machine_opts static"):

@@ -2069,13 +2068,11 @@ static int kvm_init(MachineState *ms)
     }
     s->as = g_new0(struct KVMAs, s->nr_as);

-    kvm_type = qemu_opt_get(qemu_get_machine_opts(), "kvm-type");
-    if (mc->kvm_type) {
+    if (object_property_find(OBJECT(current_machine), "kvm-type")) {
+        g_autofree char *kvm_type =
object_property_get_str(OBJECT(current_machine),
+                                                            "kvm-type",
+                                                            &error_abort);
         type = mc->kvm_type(ms, kvm_type);
-    } else if (kvm_type) {
-        ret = -EINVAL;
-        fprintf(stderr, "Invalid argument kvm-type=%s\n", kvm_type);
-        goto err;
     }

Paolo, is that expected?

So these callbacks are dead code:
hw/arm/virt.c:2585:    mc->kvm_type = virt_kvm_type;
hw/mips/loongson3_virt.c:625:    mc->kvm_type = mips_kvm_type;
hw/ppc/mac_newworld.c:598:    mc->kvm_type = core99_kvm_type;
hw/ppc/mac_oldworld.c:447:    mc->kvm_type = heathrow_kvm_type;

> 
> (Or is something hiding behind some macro magic?)
> 



  reply	other threads:[~2021-02-23 11:24 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-19 17:38 [PATCH v2 00/11] hw/accel: Exit gracefully when accelerator is invalid Philippe Mathieu-Daudé
2021-02-19 17:38 ` [PATCH v2 01/11] accel/kvm: Check MachineClass kvm_type() return value Philippe Mathieu-Daudé
2021-02-22 17:24   ` Cornelia Huck
2021-02-22 17:41     ` Philippe Mathieu-Daudé
2021-02-22 17:50       ` Cornelia Huck
2021-02-22 18:04         ` Philippe Mathieu-Daudé
2021-02-22 23:33         ` David Gibson
2021-02-22 23:37           ` David Gibson
2021-02-23 10:36             ` Cornelia Huck
2021-02-23 11:23               ` Philippe Mathieu-Daudé [this message]
2021-02-19 17:38 ` [PATCH v2 02/11] hw/boards: Introduce machine_class_valid_for_accelerator() Philippe Mathieu-Daudé
2021-02-22 17:34   ` Cornelia Huck
2021-02-22 17:46     ` Philippe Mathieu-Daudé
2021-02-22 17:59       ` Cornelia Huck
2021-02-19 17:38 ` [PATCH v2 03/11] hw/core: Restrict 'query-machines' to those supported by current accel Philippe Mathieu-Daudé
2021-02-22 17:42   ` Cornelia Huck
2021-02-19 17:38 ` [PATCH v2 04/11] hw/arm: Restrit KVM to the virt & versal machines Philippe Mathieu-Daudé
2021-02-22 20:03   ` BALATON Zoltan
2021-02-19 17:38 ` [PATCH v2 05/11] hw/mips: Restrict KVM to the malta & virt machines Philippe Mathieu-Daudé
     [not found]   ` <31a32613-2a61-7cd2-582a-4e6d10949436@flygoat.com>
2021-02-20  6:02     ` Huacai Chen
2021-02-19 17:38 ` [RFC PATCH v2 06/11] hw/ppc: Restrict KVM to various PPC machines Philippe Mathieu-Daudé
2021-02-22  5:59   ` David Gibson
2021-02-22 13:19     ` Philippe Mathieu-Daudé
2021-02-19 17:38 ` [PATCH v2 07/11] hw/s390x: Explicit the s390-ccw-virtio machines support TCG and KVM Philippe Mathieu-Daudé
2021-02-22 17:37   ` Cornelia Huck
2021-02-19 17:38 ` [RFC PATCH v2 08/11] hw/i386: Explicit x86 machines support all current accelerators Philippe Mathieu-Daudé
2021-02-19 17:38 ` [PATCH v2 09/11] hw/xenpv: Restrict Xen Para-virtualized machine to Xen accelerator Philippe Mathieu-Daudé
2021-02-19 18:20   ` Paul Durrant
2021-02-19 17:38 ` [PATCH v2 10/11] hw/board: Only allow TCG accelerator by default Philippe Mathieu-Daudé
2021-02-19 17:38 ` [PATCH v2 11/11] softmmu/vl: Exit gracefully when accelerator is not supported Philippe Mathieu-Daudé
2021-02-22 17:46   ` Cornelia Huck

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