linux-kernel - Re: [PATCH v2 3/6] KVM: x86/mmu: only zap EPT when guest MTRR changes

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: <ZFxTfaWRCfswMzMv@yzhao56-desk.sh.intel.com>
Date:   Thu, 11 May 2023 10:31:25 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     "Huang, Kai" <kai.huang@...el.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH v2 3/6] KVM: x86/mmu: only zap EPT when guest MTRR changes

On Thu, May 11, 2023 at 10:42:13AM +0800, Huang, Kai wrote:
> > > 
> > 
> > I agree shadow_memtype_mask is the right value to check but it's indeed
> > internal to kvm mmu.
> > Including "mmu/spte.h" will further include "mmu/mmu_internal.h"
> > 
> > What about introduce kvm_mmu_memtye_effective() instead as below?
> > 
> 
> [...]
> 
> >  
> > +bool kvm_mmu_memtye_effective(struct kvm *kvm)
> > +{
> > +       return shadow_memtype_mask;
> > +}
> 
> I don't think it's a good name.  shadow_memtype_mask doesn't mean any actual
> effective memtype, but just represent those bits that KVM can manipulate to get
> an effective memtype for the guest access.
> 
> Instead, it should represent the hardware capability to be able to emulate
> guest's MTRR independent from host's MTRR.  So, perhaps something like:
> 
> 	bool kvm_mmu_guest_mtrr_emulatable();

What about kvm_mmu_cap_effective_guest_mtrr()?
Guest MTRR is always emulated with vMTRR.

> 
> It's better if Sean can provide input here.
>
> (Btw, off this topic, I think it's even more reasonable to make
> shadow_memtype_mask only be meaningful when tdp_enabled is true, because the
> capability to override host MTRR and emulate guest MTRR should be only available
> when secondary MMU is turned on).
>