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

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Date:   Thu, 16 May 2019 15:25:00 +0000
From:   "Sironi, Filippo" <sironi@...zon.de>
To:     "Graf, Alexander" <graf@...zon.com>
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. 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.
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>".

Filippo


>> +}
>> +EXPORT_SYMBOL_GPL(kvm_para_get_uuid);
>> +
>> unsigned int kvm_arch_para_features(void)
>> {
>> 	return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);




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