From: Paolo Bonzini <pbonzini@redhat.com>
To: Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>, Tao Xu <tao3.xu@intel.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Jim Mattson <jmattson@google.com>,
linux-kernel@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, Wanpeng Li <wanpengli@tencent.com>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Jingqi Liu <jingqi.liu@intel.com>
Subject: Re: [PATCH 0/2] Fix issue with not starting nesting guests on my system
Date: Wed, 27 May 2020 19:00:13 +0200 [thread overview]
Message-ID: <c12376a8-fc98-5785-e4b6-5c682afd3cd6@redhat.com> (raw)
In-Reply-To: <20200523161455.3940-1-mlevitsk@redhat.com>
On 23/05/20 18:14, Maxim Levitsky wrote:
> On my AMD machine I noticed that I can't start any nested guests,
> because nested KVM (everything from master git branches) complains
> that it can't find msr MSR_IA32_UMWAIT_CONTROL which my system doesn't support
> at all anyway.
>
> I traced it to the recently added UMWAIT support to qemu and kvm.
> The kvm portion exposed the new MSR in KVM_GET_MSR_INDEX_LIST without
> checking that it the underlying feature is supported in CPUID.
> It happened to work when non nested because as a precation kvm,
> tries to read each MSR on host before adding it to that list,
> and when read gets a #GP it ignores it.
>
> When running nested, the L1 hypervisor can be set to ignore unknown
> msr read/writes (I need this for some other guests), thus this safety
> check doesn't work anymore.
>
> V2: * added a patch to setup correctly the X86_FEATURE_WAITPKG kvm capability
> * dropped the cosmetic fix patch as it is now fixed in kvm/queue
>
> Best regards,
> Maxim Levitsky
>
> Maxim Levitsky (2):
> kvm/x86/vmx: enable X86_FEATURE_WAITPKG in KVM capabilities
> kvm/x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally
>
> arch/x86/kvm/vmx/vmx.c | 3 +++
> arch/x86/kvm/x86.c | 4 ++++
> 2 files changed, 7 insertions(+)
>
Queued for 5.7, thanks (with cosmetic touches to the commit message, and
moving the "case" earlier to avoid conflicts).
Paolo
prev parent reply other threads:[~2020-05-27 17:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-23 16:14 [PATCH 0/2] Fix issue with not starting nesting guests on my system Maxim Levitsky
2020-05-23 16:14 ` [PATCH 1/2] kvm/x86/vmx: enable X86_FEATURE_WAITPKG in KVM capabilities Maxim Levitsky
2020-05-27 1:20 ` Sean Christopherson
2020-05-27 15:16 ` Maxim Levitsky
2020-05-23 16:14 ` [PATCH 2/2] kvm/x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally Maxim Levitsky
2020-05-27 1:21 ` Sean Christopherson
2020-05-27 15:17 ` Maxim Levitsky
2020-05-27 1:03 ` [PATCH 0/2] Fix issue with not starting nesting guests on my system Krish Sadhukhan
2020-05-27 1:22 ` Sean Christopherson
2020-05-27 1:13 ` Sean Christopherson
2020-05-27 15:17 ` Maxim Levitsky
2020-05-27 15:17 ` Maxim Levitsky
2020-05-27 17:00 ` Paolo Bonzini [this message]
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