From: Brijesh Singh <brijesh.singh@amd.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
Borislav Petkov <bp@suse.de>
Cc: brijesh.singh@amd.com, x86@kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
"Tom Lendacky" <thomas.lendacky@amd.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active
Date: Mon, 10 Sep 2018 10:10:09 -0500 [thread overview]
Message-ID: <097eb5f5-2cd9-8b08-32c5-d90c8e0cbb6d@amd.com> (raw)
In-Reply-To: <1536586152.11460.40.camel@intel.com>
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 ?
next prev parent reply other threads:[~2018-09-10 15:10 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 17:57 [PATCH v6 0/5] x86: Fix SEV guest regression Brijesh Singh
2018-09-07 17:57 ` [PATCH v6 1/5] x86/mm: Restructure sme_encrypt_kernel() Brijesh Singh
2018-09-10 11:32 ` Borislav Petkov
2018-09-07 17:57 ` [PATCH v6 2/5] x86/mm: fix sme_populate_pgd() to update page flags Brijesh Singh
2018-09-10 11:36 ` Borislav Petkov
2018-09-10 12:28 ` Brijesh Singh
2018-09-10 12:32 ` Borislav Petkov
2018-09-07 17:57 ` [PATCH v6 3/5] x86/mm: add .data..decrypted section to hold shared variables Brijesh Singh
2018-09-10 11:54 ` Borislav Petkov
2018-09-10 12:33 ` Brijesh Singh
2018-09-07 17:57 ` [PATCH v6 4/5] x86/kvm: use __decrypted attribute in " Brijesh Singh
2018-09-10 12:04 ` Borislav Petkov
2018-09-10 13:15 ` Sean Christopherson
2018-09-10 13:29 ` Thomas Gleixner
2018-09-10 15:34 ` Borislav Petkov
2018-09-10 12:29 ` Paolo Bonzini
2018-09-10 12:33 ` Borislav Petkov
2018-09-10 12:46 ` Paolo Bonzini
2018-09-07 17:57 ` [PATCH v6 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active Brijesh Singh
2018-09-10 12:27 ` Borislav Petkov
2018-09-10 13:15 ` Brijesh Singh
2018-09-10 13:29 ` Sean Christopherson
2018-09-10 15:10 ` Brijesh Singh [this message]
2018-09-10 15:28 ` Sean Christopherson
2018-09-10 15:30 ` Brijesh Singh
2018-09-10 16:48 ` Borislav Petkov
2018-09-11 9:26 ` Paolo Bonzini
2018-09-11 10:01 ` Borislav Petkov
2018-09-11 10:19 ` Paolo Bonzini
2018-09-11 10:25 ` Borislav Petkov
2018-09-11 11:07 ` Paolo Bonzini
2018-09-11 13:55 ` Borislav Petkov
2018-09-11 14:00 ` Paolo Bonzini
2018-09-10 15:53 ` Borislav Petkov
2018-09-10 16:13 ` Sean Christopherson
2018-09-10 16:14 ` Brijesh Singh
2018-09-10 12:28 ` Paolo Bonzini
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