linux-kernel - Re: [PATCH v4 15/19] KVM: x86: Allow FRED/LKGS to be advertised to guests

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] [day] [month] [year] [list]

Message-ID: <aFw_-8aDtO4wat8M@google.com>
Date: Wed, 25 Jun 2025 11:29:15 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Xin Li <xin@...or.com>
Cc: pbonzini@...hat.com, kvm@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, corbet@....net, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org, 
	hpa@...or.com, andrew.cooper3@...rix.com, luto@...nel.org, 
	peterz@...radead.org, chao.gao@...el.com, xin3.li@...el.com
Subject: Re: [PATCH v4 15/19] KVM: x86: Allow FRED/LKGS to be advertised to guests

On Wed, Jun 25, 2025, Xin Li wrote:
> On 6/24/2025 9:38 AM, Sean Christopherson wrote:
> > > ---
> > >   arch/x86/kvm/cpuid.c | 2 ++
> > >   1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > > index 5e4d4934c0d3..8f290273aee1 100644
> > > --- a/arch/x86/kvm/cpuid.c
> > > +++ b/arch/x86/kvm/cpuid.c
> > > @@ -992,6 +992,8 @@ void kvm_set_cpu_caps(void)
> > >   		F(FZRM),
> > >   		F(FSRS),
> > >   		F(FSRC),
> > > +		F(FRED),
> > > +		F(LKGS),
> > 
> > These need to be X86_64_F, no?
> 
> Yes.  Both LKGS and FRED are 64-bit only features.
> 
> However I assume KVM is 64-bit only now, so X86_64_F is essentially F,
> right?

Nope, KVM still supports 32-bit builds.  There are plans/efforts to kill off 32-bit
KVM x86, but we're not quite there yet.