linux-kernel - Re: KVM: x86: expose HINTS

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Message-ID: <20210816141015.31e329e3@alex-virtual-machine>
Date:   Mon, 16 Aug 2021 14:10:15 +0800
From:   Aili Yao <yaoaili@...gsoft.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
CC:     <yaoaili126@...il.com>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: KVM: x86: expose HINTS_REALTIME ablility to qemu

On Fri, 13 Aug 2021 17:54:20 +0800
Aili Yao <yaoaili@...gsoft.com> wrote:

> When I do a test that try to enable hint-dedicated for one VM, but qemu
> says "warning: host doesn't support requested feature:
> CPUID.40000001H:EDX.kvm-hint-dedicated [bit 0]".
> 
> It seems the kernel hasn't expose this ability even when supporting it;
> So expose it.

Sorry, I check it again:
Ihe issue I met is because of my qemu's mis-backport,

In qemu, kvm_arch_get_supported_cpuid() will set the feature bit:
    if (function == KVM_CPUID_FEATURES && reg == R_EDX) {
        ret |= KVM_HINTS_DEDICATED;
        found = 1;
    }
But I have mis-ported the KVM_HINTS_DEDICATED and KVM_HINTS_REALTIME macro; And it lead to
the error I met;

And it's right that kernel don't expose this ability!

Sorry again!