linux-kernel - Re: [PATCH v15 22/23] x86/mce: Improve error log of kernel space TDX #MC due to erratum

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Message-ID: <ae972860-cc45-48b0-ba3e-bb2fbad5856a@intel.com>
Date:   Tue, 5 Dec 2023 08:36:10 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Kai Huang <kai.huang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        Chao Gao <chao.gao@...el.com>, Tony Luck <tony.luck@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        "nik.borisov@...e.com" <nik.borisov@...e.com>,
        "hpa@...or.com" <hpa@...or.com>,
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        "peterz@...radead.org" <peterz@...radead.org>,
        "bp@...en8.de" <bp@...en8.de>, Len Brown <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Ying Huang <ying.huang@...el.com>,
        Dan J Williams <dan.j.williams@...el.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v15 22/23] x86/mce: Improve error log of kernel space TDX
 #MC due to erratum

On 12/4/23 18:04, Sean Christopherson wrote:
> Joking aside, why shove TDX module ownership into KVM?  It honestly sounds like
> a terrible fit, even without the whole TDX-IO mess.  KVM state is largely ephemeral,
> in the sense that loading and unloading kvm.ko doesn't allocate/free much memory
> or do all that much initialization or teardown.

Yeah, you have a good point there.  We really do need some core code to
manage VMXON/OFF now that there is increased interest outside of
_purely_ running VMs.

For the purposes of _this_ patch, I think I'm happy to leave open the
possibility that SEAMCALL can simply fail due to VMXOFF.  For now, it
means that we can't attribute #MC's to the PAMT unless a VM is running
but that seems like a reasonable compromise for the moment.

Once TDX gains the ability to "pin" VMXON, the added precision here will
be appreciated.