From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Vitaly Kuznetsov <vkuznets@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: Tue, 15 Sep 2020 17:51:31 +0100 [thread overview]
Message-ID: <20200915165131.GC2922@work-vm> (raw)
In-Reply-To: <20200915154306.724953-1-vkuznets@redhat.com>
* Vitaly Kuznetsov (vkuznets@redhat.com) wrote:
> With QEMU and newer AMD CPUs (namely: Epyc 'Rome') the current limit for
> KVM_MAX_CPUID_ENTRIES(80) is reported to be hit. Last time it was raised
> from '40' in 2010. We can, of course, just bump it a little bit to fix
> the immediate issue but the report made me wonder why we need to pre-
> allocate vcpu->arch.cpuid_entries array instead of sizing it dynamically.
> This RFC is intended to feed my curiosity.
>
> Very mildly tested with selftests/kvm-unit-tests and nothing seems to
> break. I also don't have access to the system where the original issue
> was reported but chances we're fixing it are very good IMO as just the
> second patch alone was reported to be sufficient.
>
> Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Oh nice, I was just going to bump the magic number :-)
Anyway, this seems to work for me, so:
Tested-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Vitaly Kuznetsov (2):
> KVM: x86: allocate vcpu->arch.cpuid_entries dynamically
> KVM: x86: bump KVM_MAX_CPUID_ENTRIES
>
> arch/x86/include/asm/kvm_host.h | 4 +--
> arch/x86/kvm/cpuid.c | 55 ++++++++++++++++++++++++---------
> arch/x86/kvm/x86.c | 1 +
> 3 files changed, 43 insertions(+), 17 deletions(-)
>
> --
> 2.25.4
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2020-09-15 19:49 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 ` Dr. David Alan Gilbert [this message]
2020-09-16 3:49 ` [PATCH RFC 0/2] KVM: x86: allow for more CPUID entries Wei Huang
2020-09-16 7:44 ` Vitaly Kuznetsov
2020-09-16 8:33 ` Dr. David Alan Gilbert
2020-09-16 19:22 ` Wei Huang
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