From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Wei Huang <wei.huang2@amd.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Wei Huang <whuang2@amd.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC 0/2] KVM: x86: allow for more CPUID entries
Date: Wed, 16 Sep 2020 09:44:55 +0200 [thread overview]
Message-ID: <87k0wui2rs.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200916034905.GA508748@weilap>
Wei Huang <wei.huang2@amd.com> writes:
> On 09/15 05:51, Dr. David Alan Gilbert wrote:
>> * Vitaly Kuznetsov (vkuznets@redhat.com) wrote:
>> > With QEMU and newer AMD CPUs (namely: Epyc 'Rome') the current limit for
>
> Could you elaborate on this limit? On Rome, I counted ~35 CPUID functions which
> include Fn0000_xxxx, Fn4000_xxxx and Fn8000_xxxx.
Some CPUID functions have indicies (e.g. 0x00000004, 0x8000001d, ...)
and each existing index requires a separate entry. E.g. on my AMD EPYC
7401P host I can see:
# cpuid -r -1 | wc -l
53
Hyper-V emulation accounts for 11 leaves (we don't currently set them
all in QEMU but eventually we will). Also, we sometimes set both Intel
and AMD cpuid leaves in QEMU (David can probably elaborate on which/why)
and this all adds up. '80' seems to be an easy target to hit even with
existing CPUs :-)
--
Vitaly
next prev parent reply other threads:[~2020-09-16 7:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 15:43 [PATCH RFC 0/2] KVM: x86: allow for more CPUID entries Vitaly Kuznetsov
2020-09-15 15:43 ` [PATCH RFC 1/2] KVM: x86: allocate vcpu->arch.cpuid_entries dynamically Vitaly Kuznetsov
2020-09-18 2:41 ` Sean Christopherson
2020-10-01 10:04 ` Vitaly Kuznetsov
2020-09-15 15:43 ` [PATCH RFC 2/2] KVM: x86: bump KVM_MAX_CPUID_ENTRIES Vitaly Kuznetsov
2020-09-15 16:51 ` [PATCH RFC 0/2] KVM: x86: allow for more CPUID entries Dr. David Alan Gilbert
2020-09-16 3:49 ` Wei Huang
2020-09-16 7:44 ` Vitaly Kuznetsov [this message]
2020-09-16 8:33 ` Dr. David Alan Gilbert
2020-09-16 19:22 ` Wei Huang
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