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From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Yang Weijiang <weijiang.yang@intel.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	jmattson@google.com, yu.c.zhang@linux.intel.com
Subject: Re: [PATCH v14 00/13] Introduce support for guest CET feature
Date: Thu, 28 Jan 2021 10:24:55 -0800	[thread overview]
Message-ID: <YBMBd1qxvQh47zcB@google.com> (raw)
In-Reply-To: <32c9cdf7-7432-1212-2fe4-fe35ad27105a@redhat.com>

On Thu, Jan 28, 2021, Paolo Bonzini wrote:
> On 28/01/21 19:04, Sean Christopherson wrote:
> > On Thu, Jan 28, 2021, Paolo Bonzini wrote:
> > > On 06/11/20 02:16, Yang Weijiang wrote:
> > > > Control-flow Enforcement Technology (CET) provides protection against
> > > > Return/Jump-Oriented Programming (ROP/JOP) attack. There're two CET
> > > > sub-features: Shadow Stack (SHSTK) and Indirect Branch Tracking (IBT).
> > > > SHSTK is to prevent ROP programming and IBT is to prevent JOP programming.
> > 
> > ...
> > 
> > > I reviewed the patch and it is mostly okay.  However, if I understand it
> > > correctly, it will not do anything until host support materializes, because
> > > otherwise XSS will be 0.
> > 
> > IIRC, it won't even compile due to the X86_FEATURE_SHSTK and X86_FEATURE_IBT
> > dependencies.
> 
> Of course, but if that was the only issue I would sort it out with Boris as
> usual.  OTOH if it is dead code I won't push it to Linus.

Yes, at best it's dead code.  At worst, if it somehow became undead, the guest
state would bleed into the host and wouldn't be migrated as the kernel wouldn't
touch CET state when doing XSAVES/XRSTORS.

I floated the idea of pulling in just enough of the kernel bits to enable KVM,
but that didn't go anywhere.

https://lkml.kernel.org/r/20200723162531.GF21891@linux.intel.com

      reply	other threads:[~2021-01-28 18:29 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-06  1:16 [PATCH v14 00/13] Introduce support for guest CET feature Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 01/13] KVM: x86: Report XSS as an MSR to be saved if there are supported features Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 02/13] KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 03/13] KVM: x86: Add #CP support in guest exception dispatch Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 04/13] KVM: VMX: Introduce CET VMCS fields and flags Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 05/13] KVM: x86: Add fault checks for CR4.CET Yang Weijiang
2020-11-09 10:44   ` kernel test robot
2020-11-06  1:16 ` [PATCH v14 06/13] KVM: x86: Load guest fpu state when accessing MSRs managed by XSAVES Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 07/13] KVM: VMX: Emulate reads and writes to CET MSRs Yang Weijiang
2021-01-28 17:45   ` Paolo Bonzini
2021-01-29  8:07     ` Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 08/13] KVM: VMX: Add a synthetic MSR to allow userspace VMM to access GUEST_SSP Yang Weijiang
2021-01-28 17:41   ` Paolo Bonzini
2021-01-28 17:42   ` Paolo Bonzini
2020-11-06  1:16 ` [PATCH v14 09/13] KVM: x86: Report CET MSRs as to-be-saved if CET is supported Yang Weijiang
2020-11-09  6:17   ` kernel test robot
2021-01-28 17:46   ` Paolo Bonzini
2021-01-29  8:08     ` Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 10/13] KVM: x86: Enable CET virtualization for VMX and advertise CET to userspace Yang Weijiang
2020-11-09  7:23   ` kernel test robot
2021-01-28 17:53   ` Paolo Bonzini
     [not found]     ` <20210129112437.GA29715@local-michael-cet-test.sh.intel.com>
     [not found]       ` <68e288ee-6e09-36f1-a6c9-bed864eb7678@redhat.com>
     [not found]         ` <20210129121717.GA30243@local-michael-cet-test.sh.intel.com>
     [not found]           ` <1cf7e501-2c69-8b76-9332-42db1348ab08@redhat.com>
2021-01-30  6:32             ` Yang Weijiang
2021-02-01  4:56             ` Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 11/13] KVM: VMX: Pass through CET MSRs to the guest when supported Yang Weijiang
2021-01-28 17:54   ` Paolo Bonzini
2021-01-28 18:04     ` Paolo Bonzini
2020-11-06  1:16 ` [PATCH v14 12/13] KVM: nVMX: Add helper to check the vmcs01 MSR bitmap for MSR pass-through Yang Weijiang
2020-11-06  1:16 ` [PATCH v14 13/13] KVM: nVMX: Enable CET support for nested VMX Yang Weijiang
2021-01-28 17:57 ` [PATCH v14 00/13] Introduce support for guest CET feature Paolo Bonzini
2021-01-28 18:04   ` Sean Christopherson
2021-01-28 18:06     ` Paolo Bonzini
2021-01-28 18:24       ` Sean Christopherson [this message]

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