linux-kernel - Re: [PATCH v3 13/21] KVM:VMX: Emulate reads and writes to CET MSRs

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: <30c89021-5b82-c676-bb58-1b572e57436a@linux.intel.com>
Date:   Tue, 23 May 2023 16:21:27 +0800
From:   Binbin Wu <binbin.wu@...ux.intel.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     seanjc@...gle.com, pbonzini@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        rppt@...nel.org, rick.p.edgecombe@...el.com, john.allen@....com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v3 13/21] KVM:VMX: Emulate reads and writes to CET MSRs



On 5/11/2023 12:08 PM, Yang Weijiang wrote:
> Add support for emulating read and write accesses to CET MSRs.
> CET MSRs are universally "special" as they are either context switched
> via dedicated VMCS fields or via XSAVES, i.e. no additional in-memory
> tracking is needed, but emulated reads/writes are more expensive.
>
> Co-developed-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
> ---
>   arch/x86/kernel/fpu/core.c |  1 +
>   arch/x86/kvm/vmx/vmx.c     | 18 ++++++++++++++++++
>   arch/x86/kvm/x86.c         | 20 ++++++++++++++++++++
>   arch/x86/kvm/x86.h         | 31 +++++++++++++++++++++++++++++++
>   4 files changed, 70 insertions(+)
>
...
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b6eec9143129..2e3a39c9297c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -13630,6 +13630,26 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
>   }
>   EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);
>   
> +bool kvm_cet_is_msr_accessible(struct kvm_vcpu *vcpu, struct msr_data *msr)
> +{
> +	if (!kvm_cet_user_supported())
> +		return false;
> +
> +	if (msr->host_initiated)
> +		return true;
> +
> +	if (!guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) &&
> +	    !guest_cpuid_has(vcpu, X86_FEATURE_IBT))
> +		return false;
> +
> +	if (msr->index == MSR_IA32_PL3_SSP &&
> +	    !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK))
> +		return false;
It may be better to merge the two if statements into one to avoid 
calling guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) twice.

e.g,

     if (!guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) &&
         (!guest_cpuid_has(vcpu, X86_FEATURE_IBT) || msr->index == 
MSR_IA32_PL3_SSP))
         return false;


> +
> +	return true;
> +}
> +EXPORT_SYMBOL_GPL(kvm_cet_is_msr_accessible);
> +
>   EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry);
>   EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
>   EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
>
...