linux-kernel - Re: [PATCH v3 0/7] arm64: add system vulnerability sysfs entries

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Date:   Fri, 18 Jan 2019 16:22:16 -0600
From:   Jeremy Linton <jeremy.linton@....com>
To:     Stefan Wahren <stefan.wahren@...e.com>, marc.zyngier@....com
Cc:     mlangsdo@...hat.com, suzuki.poulose@....com,
        linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
        julien.thierry@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org, steven.price@....com,
        ykaukab@...e.de, dave.martin@....com, shankerd@...eaurora.org
Subject: Re: [PATCH v3 0/7] arm64: add system vulnerability sysfs entries

On 01/18/2019 12:05 PM, Stefan Wahren wrote:
> Hi,
> 
>> Jeremy Linton <jeremy.linton@....com> hat am 15. Januar 2019 um 22:21 geschrieben:
>>
>>
>> Hi,
>>
>> On 01/15/2019 01:50 PM, Stefan Wahren wrote:
>>> Hi Jeremy,
>>>
>>>> Jeremy Linton <jeremy.linton@....com> hat am 10. Januar 2019 um 00:55 geschrieben:
>>>>
>>>>
>>>> Arm64 machines should be displaying a human readable
>>>> vulnerability status to speculative execution attacks in
>>>> /sys/devices/system/cpu/vulnerabilities
>>>>
>>>> This series enables that behavior by providing the expected
>>>> functions. Those functions expose the cpu errata and feature
>>>> states, as well as whether firmware is responding appropriately
>>>> to display the overall machine status. This means that in a
>>>> heterogeneous machine we will only claim the machine is mitigated
>>>> or safe if we are confident all booted cores are safe or
>>>> mitigated.
>>>>
>>>
>>> i applied this v3 series and Marc's v2 series.
>>>
>>> Now i'm getting the following on a Raspberry Pi 3 B+ :
>>>
>>> meltdown:Not affected
>>> spec_store_bypass:Not affected
>>> spectre_v1:Mitigation: __user pointer sanitization
>>>
>>> So the entries l1tf and spectre_v2 disappeared.
>>
>> Yes, the l1tf entry should be gone.
>>
>> I believe there is a problem with the "1/2 advertise.." patch in that
>> the 'arm64_requested_vuln_attrs |=' line needs to be hoisted  to the top
>> of check_branch_predictor() and the '__spectrev2_safe = false' line
>> needs to be hoisted 6 lines immediately above "/* Fallback to firmware
>> detection*/"
> 
> a snippet or a new version would be nice

Sure, I've got another version, to be posted soon (probably Tue of next 
week).

In the meantime, Marc's tree should work with the following fix:

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index b44f87e7360d..7cfd34b2c0e5 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -286,11 +286,15 @@ static int detect_harden_bp_fw(void)
  }
  #endif /* CONFIG_HARDEN_BRANCH_PREDICTOR */

+#if defined(CONFIG_ARM64_SSBD) || \
+       defined(CONFIG_GENERIC_CPU_VULNERABILITIES)
+static bool __ssb_safe = true;
+#endif
+
  #ifdef CONFIG_ARM64_SSBD
  DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);

  int ssbd_state __read_mostly = ARM64_SSBD_KERNEL;
-static bool __ssb_safe = true;

  static const struct ssbd_options {
         const char      *str;
@@ -569,6 +573,8 @@ check_branch_predictor(const struct 
arm64_cpu_capabilities *entry, int scope)

         WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());

+       arm64_requested_vuln_attrs |= VULN_SPECTREV2;
+
         /* If the CPU has CSV2 set, we're safe */
         if 
(cpuid_feature_extract_unsigned_field(read_cpuid(ID_AA64PFR0_EL1),
                                                  ID_AA64PFR0_CSV2_SHIFT))
@@ -578,17 +584,17 @@ check_branch_predictor(const struct 
arm64_cpu_capabilities *entry, int scope)
         if (is_midr_in_range_list(read_cpuid_id(), spectre_v2_safe_list))
                 return false;

+       __spectrev2_safe = false;
+
         /* Fallback to firmware detection */
         need_wa = detect_harden_bp_fw();
         if (!need_wa)
                 return false;

-       __spectrev2_safe = false;
-
         if (need_wa < 0)
                 pr_warn_once("ARM_SMCCC_ARCH_WORKAROUND_1 missing from 
firmware\n");

-       arm64_requested_vuln_attrs |= VULN_SPECTREV2;
+

         return (need_wa > 0);
  }