¿IBRS o Reptoline?

[Krovikan]

Hola:


En Phoronix (aquí) hablan de cómo openSUSE utiliza IBRS para mitigar Spectre v2 lo que hace bajar el rendimiento del Sistema un 23%.

Si en lugar de IBRS se usará Reptoline (como todas, o casi, las distribuciones) no se perdería ese 23% de rendimiento. Si no entendí mal, para usar Reptoline es añadir a la línea de parámetros del kernel (que imagino es la que pone splash, vga, etc etc) el parámetro:

spectre_v2=retpoline,generic

En esta lista de correo de openSUSE:

https://lists.opensuse.org/opensuse-.../msg00140.html

se habla del tema y hay un enlace que lleva a una comparativa entre un sistema mitigado con IBRS (1ª columna) y el mismo sistema pero mitigado con Reptoline (2ª columna). El aumento de rendimiento es considerable.


No entiendo en qué consiste uno y otro. Tampoco me queda claro (como dicen en la lista de openSUSE) si tengo la opción o no de elegir entre ambos modos (y sus ventajas e inconvenientes aparte del 23% de rendimiento).

Mi búsqueda en Internet no me aclara nada (demasiado técnico para mi) de qué es una cosa y qué es otra. Mi CPU es Skylake (i5 6600K).


Saludos

[DiabloRojo]

No conocía esa opción, pero si lo quieres tenerlo tendrás que compilar tu mismo el kernel.
Lo que no entiendo es porque usa IBRS en TW.

[Krovikan]

Leap también usa IBRS.

krovikan@linux:~/Descargas> sudo sh spectre-meltdown-checker.sh 
[sudo] password for root: 
Spectre and Meltdown mitigation detection tool v0.40

Checking for vulnerabilities on current system
Kernel is Linux 5.0.6-1.gdff56e4-default #1 SMP Thu Apr 4 04:40:16 UTC 2019 (dff56e4) x86_64
CPU is Intel(R) Core(TM) i5-6600K CPU @ 3.50GHz

Hardware check
* Hardware support (CPU microcode) for mitigation techniques
  * Indirect Branch Restricted Speculation (IBRS)
    * SPEC_CTRL MSR is available:  YES 
    * CPU indicates IBRS capability:  YES  (SPEC_CTRL feature bit)
  * Indirect Branch Prediction Barrier (IBPB)
    * PRED_CMD MSR is available:  YES 
    * CPU indicates IBPB capability:  YES  (SPEC_CTRL feature bit)
  * Single Thread Indirect Branch Predictors (STIBP)
    * SPEC_CTRL MSR is available:  YES 
    * CPU indicates STIBP capability:  YES  (Intel STIBP feature bit)
  * Speculative Store Bypass Disable (SSBD)
    * CPU indicates SSBD capability:  YES  (Intel SSBD)
  * L1 data cache invalidation
    * FLUSH_CMD MSR is available:  YES 
    * CPU indicates L1D flush capability:  YES  (L1D flush feature bit)
  * Enhanced IBRS (IBRS_ALL)
    * CPU indicates ARCH_CAPABILITIES MSR availability:  NO 
    * ARCH_CAPABILITIES MSR advertises IBRS_ALL capability:  NO 
  * CPU explicitly indicates not being vulnerable to Meltdown (RDCL_NO):  NO 
  * CPU explicitly indicates not being vulnerable to Variant 4 (SSB_NO):  NO 
  * CPU/Hypervisor indicates L1D flushing is not necessary on this system:  NO 
  * Hypervisor indicates host CPU might be vulnerable to RSB underflow (RSBA):  NO 
  * CPU supports Software Guard Extensions (SGX):  YES 
  * CPU microcode is known to cause stability problems:  NO  (model 0x5e family 0x6 stepping 0x3 ucode 0xc6 cpuid 0x506e3)
  * CPU microcode is the latest known available version:  YES  (latest version is 0xc6 dated 2018/04/17 according to builtin MCExtractor DB v96 - 2019/01/15)
* CPU vulnerability to the speculative execution attack variants
  * Vulnerable to CVE-2017-5753 (Spectre Variant 1, bounds check bypass):  YES 
  * Vulnerable to CVE-2017-5715 (Spectre Variant 2, branch target injection):  YES 
  * Vulnerable to CVE-2017-5754 (Variant 3, Meltdown, rogue data cache load):  YES 
  * Vulnerable to CVE-2018-3640 (Variant 3a, rogue system register read):  YES 
  * Vulnerable to CVE-2018-3639 (Variant 4, speculative store bypass):  YES 
  * Vulnerable to CVE-2018-3615 (Foreshadow (SGX), L1 terminal fault):  YES 
  * Vulnerable to CVE-2018-3620 (Foreshadow-NG (OS), L1 terminal fault):  YES 
  * Vulnerable to CVE-2018-3646 (Foreshadow-NG (VMM), L1 terminal fault):  YES 

CVE-2017-5753 aka 'Spectre Variant 1, bounds check bypass'
* Mitigated according to the /sys interface:  YES  (Mitigation: __user pointer sanitization)
* Kernel has array_index_mask_nospec:  YES  (1 occurrence(s) found of x86 64 bits array_index_mask_nospec())
* Kernel has the Red Hat/Ubuntu patch:  NO 
* Kernel has mask_nospec64 (arm64):  NO 
> STATUS:  NOT VULNERABLE  (Mitigation: __user pointer sanitization)

CVE-2017-5715 aka 'Spectre Variant 2, branch target injection'
* Mitigated according to the /sys interface:  YES  (Mitigation: Indirect Branch Restricted Speculation, IBPB: conditional, IBRS_FW, STIBP: disabled, RSB filling)
* Mitigation 1
  * Kernel is compiled with IBRS support:  YES 
    * IBRS enabled and active:  YES  (for kernel and firmware code)
  * Kernel is compiled with IBPB support:  YES 
    * IBPB enabled and active:  YES 
* Mitigation 2
  * Kernel has branch predictor hardening (arm):  NO 
  * Kernel compiled with retpoline option:  YES 
  * Kernel supports RSB filling:  YES 
> STATUS:  NOT VULNERABLE  (IBRS + IBPB are mitigating the vulnerability)

CVE-2017-5754 aka 'Variant 3, Meltdown, rogue data cache load'
* Mitigated according to the /sys interface:  YES  (Mitigation: PTI)
* Kernel supports Page Table Isolation (PTI):  YES 
  * PTI enabled and active:  YES 
  * Reduced performance impact of PTI:  YES  (CPU supports INVPCID, performance impact of PTI will be greatly reduced)
* Running as a Xen PV DomU:  NO 
> STATUS:  NOT VULNERABLE  (Mitigation: PTI)

CVE-2018-3640 aka 'Variant 3a, rogue system register read'
* CPU microcode mitigates the vulnerability:  YES 
> STATUS:  NOT VULNERABLE  (your CPU microcode mitigates the vulnerability)

CVE-2018-3639 aka 'Variant 4, speculative store bypass'
* Mitigated according to the /sys interface:  YES  (Mitigation: Speculative Store Bypass disabled via prctl and seccomp)
* Kernel supports speculation store bypass:  YES  (found in /proc/self/status)
> STATUS:  NOT VULNERABLE  (Mitigation: Speculative Store Bypass disabled via prctl and seccomp)

CVE-2018-3615 aka 'Foreshadow (SGX), L1 terminal fault'
* CPU microcode mitigates the vulnerability:  YES 
> STATUS:  NOT VULNERABLE  (your CPU microcode mitigates the vulnerability)

CVE-2018-3620 aka 'Foreshadow-NG (OS), L1 terminal fault'
* Mitigated according to the /sys interface:  YES  (Mitigation: PTE Inversion)
* Kernel supports PTE inversion:  YES  (found in kernel image)
* PTE inversion enabled and active:  YES 
> STATUS:  NOT VULNERABLE  (Mitigation: PTE Inversion)

CVE-2018-3646 aka 'Foreshadow-NG (VMM), L1 terminal fault'
* Information from the /sys interface: VMX: conditional cache flushes, SMT disabled
* This system is a host running a hypervisor:  NO 
* Mitigation 1 (KVM)
  * EPT is disabled:  NO 
* Mitigation 2
  * L1D flush is supported by kernel:  YES  (found flush_l1d in /proc/cpuinfo)
  * L1D flush enabled:  YES  (conditional flushes)
  * Hardware-backed L1D flush supported:  YES  (performance impact of the mitigation will be greatly reduced)
  * Hyper-Threading (SMT) is enabled:  NO 
> STATUS:  NOT VULNERABLE  (this system is not running a hypervisor)

> SUMMARY: CVE-2017-5753:OK CVE-2017-5715:OK CVE-2017-5754:OK CVE-2018-3640:OK CVE-2018-3639:OK CVE-2018-3615:OK CVE-2018-3620:OK CVE-2018-3646:OK

Saludos

[DiabloRojo]

Pues debe ser que viene de la casa matriz, supongo.