linux-kernel - Re: [PATCH v2 2/2] KVM: x86: Implement the arch-specific hook to report the VM UUID

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Message-ID: <8c6a2de2-f080-aad5-16af-c4a5eafb31af@amazon.com>
Date:   Thu, 16 May 2019 08:33:49 -0700
From:   Alexander Graf <graf@...zon.com>
To:     "Sironi, Filippo" <sironi@...zon.de>
CC:     LKML <linux-kernel@...r.kernel.org>,
        KVM list <kvm@...r.kernel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "vasu.srinivasan@...cle.com" <vasu.srinivasan@...cle.com>
Subject: Re: [PATCH v2 2/2] KVM: x86: Implement the arch-specific hook to
 report the VM UUID


On 16.05.19 08:25, Sironi, Filippo wrote:
>> On 16. May 2019, at 15:56, Graf, Alexander <graf@...zon.com> wrote:
>>
>> On 14.05.19 08:16, Filippo Sironi wrote:
>>> On x86, we report the UUID in DMI System Information (i.e., DMI Type 1)
>>> as VM UUID.
>>>
>>> Signed-off-by: Filippo Sironi <sironi@...zon.de>
>>> ---
>>> arch/x86/kernel/kvm.c | 7 +++++++
>>> 1 file changed, 7 insertions(+)
>>>
>>> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
>>> index 5c93a65ee1e5..441cab08a09d 100644
>>> --- a/arch/x86/kernel/kvm.c
>>> +++ b/arch/x86/kernel/kvm.c
>>> @@ -25,6 +25,7 @@
>>> #include <linux/kernel.h>
>>> #include <linux/kvm_para.h>
>>> #include <linux/cpu.h>
>>> +#include <linux/dmi.h>
>>> #include <linux/mm.h>
>>> #include <linux/highmem.h>
>>> #include <linux/hardirq.h>
>>> @@ -694,6 +695,12 @@ bool kvm_para_available(void)
>>> }
>>> EXPORT_SYMBOL_GPL(kvm_para_available);
>>>
>>> +const char *kvm_para_get_uuid(void)
>>> +{
>>> +	return dmi_get_system_info(DMI_PRODUCT_UUID);
>> This adds a new dependency on CONFIG_DMI. Probably best to guard it with
>> an #if IS_ENABLED(CONFIG_DMI).
>>
>> The concept seems sound though.
>>
>> Alex
> include/linux/dmi.h contains a dummy implementation of
> dmi_get_system_info that returns NULL if CONFIG_DMI isn't defined.


Oh, I missed that bit. Awesome! Less work :).


> This is enough unless we decide to return "<denied>" like in Xen.
> If then, we can have the check in the generic code to turn NULL
> into "<denied>".


Yes. Waiting for someone from Xen to answer this :)


Alex