linux-kernel - Re: [PATCH 2/4] KVM: x86/mmu: Defer "full" MMU setup until after vendor hardware

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YtBfPU4lhPbuDJ3y@google.com>
Date:   Thu, 14 Jul 2022 18:23:57 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] KVM: x86/mmu: Defer "full" MMU setup until after
 vendor hardware_setup()

On Tue, Jul 12, 2022, Peter Xu wrote:
> On Fri, Jun 24, 2022 at 11:27:33PM +0000, Sean Christopherson wrote:
> > @@ -11937,6 +11932,10 @@ int kvm_arch_hardware_setup(void *opaque)
> >  
> >  	kvm_ops_update(ops);
> >  
> > +	r = kvm_mmu_hardware_setup();
> > +	if (r)
> > +		goto out_unsetup;
> > +
> >  	kvm_register_perf_callbacks(ops->handle_intel_pt_intr);
> >  
> >  	if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
> > @@ -11960,12 +11959,18 @@ int kvm_arch_hardware_setup(void *opaque)
> >  	kvm_caps.default_tsc_scaling_ratio = 1ULL << kvm_caps.tsc_scaling_ratio_frac_bits;
> >  	kvm_init_msr_list();
> >  	return 0;
> > +
> > +out_unsetup:
> > +	static_call(kvm_x86_hardware_unsetup)();
> 
> Should this be kvm_mmu_hardware_unsetup()?  Or did I miss something?..

There is no kvm_mmu_hardware_unsetup().  This path is called if kvm_mmu_hardware_setup()
fails, i.e. the common code doesn't need to unwind anything.

The vendor call is not shown in the patch diff, but it's before this as:

	r = ops->hardware_setup();
	if (r != 0)
		return r

there's no existing error paths after that runs, which is why the vendor unsetup
call is new.