linux-kernel - Re: [PATCH RFC 3/7] kvm: x86: XSAVE state and XFD MSRs context switch

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]

Date:   Mon, 8 Feb 2021 11:25:07 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jing Liu <jing2.liu@...ux.intel.com>, seanjc@...gle.com,
        kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, jing2.liu@...el.com
Subject: Re: [PATCH RFC 3/7] kvm: x86: XSAVE state and XFD MSRs context switch

On 07/02/21 16:42, Jing Liu wrote:
> |In KVM, "guest_fpu" serves for any guest task working on this vcpu 
> during vmexit and vmenter. We provide a pre-allocated guest_fpu space 
> and entire "guest_fpu.state_mask" to avoid each dynamic features 
> detection on each vcpu task. Meanwhile, to ensure correctly 
> xsaves/xrstors guest state, set IA32_XFD as zero during vmexit and vmenter.|

Most guests will not need the whole xstate feature set.  So perhaps you 
  could set XFD to the host value | the guest value, trap #NM if the 
host XFD is zero, and possibly reflect the exception to the guest's XFD 
and XFD_ERR.

In addition, loading the guest XFD MSRs should use the MSR autoload 
feature (add_atomic_switch_msr).

Paolo