Messages in this thread | | | Subject | Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active | From | Brijesh Singh <> | Date | Mon, 10 Sep 2018 10:10:09 -0500 |
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On 09/10/2018 08:29 AM, Sean Christopherson wrote: ...
>>>> + */ >>>> +static struct pvclock_vsyscall_time_info >>>> + hv_clock_aux[NR_CPUS] __decrypted_aux; >>> Hmm, so worst case that's 64 4K pages: >>> >>> (8192*32)/4096 = 64 4K pages. >> We can minimize the worst case memory usage. The number of VCPUs >> supported by KVM maybe less than NR_CPUS. e.g Currently KVM_MAX_VCPUS is >> set to 288 > > KVM_MAX_VCPUS is a property of the host, whereas this code runs in the > guest, e.g. KVM_MAX_VCPUS could be 2048 in the host for all we know. >
IIRC, during guest creation time qemu will check the host supported VCPUS count. If count is greater than KVM_MAX_VCPUS then it will fail to launch guest (or fail to hot plug vcpus). In other words, the number of vcpus in a KVM guest will never to > KVM_MAX_VCPUS.
Am I missing something ?
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