From: Bandan Das <bsd@redhat.com>
To: Hardik H Bagdi <hbagdi1@binghamton.edu>
Cc: kvm@vger.kernel.org
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: KVM_MAX_VCPU hard limit of 255 on x86
Date: Fri, 01 Apr 2016 17:55:07 -0400 [thread overview]
Message-ID: <jpgd1q9q9j8.fsf@linux.bootlegged.copy> (raw)
In-Reply-To: <CADdiZBSsL+T8gTgEjwcLYiMM_CunAeWykBouUPA5HfO8s2iSgw@mail.gmail.com> (Hardik H. Bagdi's message of "Fri, 1 Apr 2016 17:19:47 -0400")
Hardik H Bagdi <hbagdi1@binghamton.edu> writes:
> Hello,
>
> For research, I am experimenting with increasing the number of VCPUs
> in the guest OS.
> I can increase the number of VCPUs till 255 in the guest OS but more
> than that results in the following error-
>
> kvm_init_vcpu failed: Invalid argument
>
> The hardcodede value of 255 can be found here for x86.
> ./arch/x86/include/asm/kvm_host.h:38:#define KVM_MAX_VCPUS 255
>
> #define a new value is not successful i.e. the same error persists.
> I'm using qemu 2.5.0 with host kernel 3.19.0
> Any help will be really appreciated.
Radim (Cced) might have more info but the short answer is that you
can't just simply increase the number. For >255, you need x2apic
with interrupt remapping which is still missing.
> Thank you,
> Hardik Bagdi
> --
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next prev parent reply other threads:[~2016-04-01 21:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-01 21:19 KVM_MAX_VCPU hard limit of 255 on x86 Hardik H Bagdi
2016-04-01 21:55 ` Bandan Das [this message]
2016-04-04 15:17 ` Radim Krčmář
2016-04-04 19:14 ` Igor Mammedov
2016-04-04 20:34 ` Radim Krčmář
2016-04-05 11:20 ` Igor Mammedov
2016-04-05 14:01 ` Radim Krčmář
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