linux-hardening - Re: [PATCH v1 6/9] KVM: x86: Add Heki hypervisor support

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Date:   Mon, 8 May 2023 21:18:29 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Alexander Graf <graf@...zon.com>,
        Forrest Yuan Yu <yuanyu@...gle.com>,
        James Morris <jamorris@...ux.microsoft.com>,
        John Andersen <john.s.andersen@...el.com>,
        Liran Alon <liran.alon@...cle.com>,
        "Madhavan T . Venkataraman" <madvenka@...ux.microsoft.com>,
        Marian Rotariu <marian.c.rotariu@...il.com>,
        Mihai Donțu <mdontu@...defender.com>,
        Nicușor Cîțu <nicu.citu@...oud.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Thara Gopinath <tgopinath@...rosoft.com>,
        Will Deacon <will@...nel.org>,
        Zahra Tarkhani <ztarkhani@...rosoft.com>,
        Ștefan Șicleru <ssicleru@...defender.com>,
        dev@...ts.cloudhypervisor.org, kvm@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, qemu-devel@...gnu.org,
        virtualization@...ts.linux-foundation.org, x86@...nel.org,
        xen-devel@...ts.xenproject.org, Wei Liu <wei.liu@...nel.org>
Subject: Re: [PATCH v1 6/9] KVM: x86: Add Heki hypervisor support

On Fri, May 05, 2023 at 05:20:43PM +0200, Mickaël Salaün wrote:
> From: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com>
> 
> Each supported hypervisor in x86 implements a struct x86_hyper_init to
> define the init functions for the hypervisor.  Define a new init_heki()
> entry point in struct x86_hyper_init.  Hypervisors that support Heki
> must define this init_heki() function.  Call init_heki() of the chosen
> hypervisor in init_hypervisor_platform().
> 
> Create a heki_hypervisor structure that each hypervisor can fill
> with its data and functions. This will allow the Heki feature to work
> in a hypervisor agnostic way.
> 
> Declare and initialize a "heki_hypervisor" structure for KVM so KVM can
> support Heki.  Define the init_heki() function for KVM.  In init_heki(),
> set the hypervisor field in the generic "heki" structure to the KVM
> "heki_hypervisor".  After this point, generic Heki code can access the
> KVM Heki data and functions.
> 
[...]
> +static void kvm_init_heki(void)
> +{
> +	long err;
> +
> +	if (!kvm_para_available())
> +		/* Cannot make KVM hypercalls. */
> +		return;
> +
> +	err = kvm_hypercall3(KVM_HC_LOCK_MEM_PAGE_RANGES, -1, -1, -1);

Why not do a proper version check or capability check here? If the ABI
or supported features ever change then we have something to rely on?

Thanks,
Wei.