Re: [PATCH 5.10 11/14] arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 877ace9eab7de032f954533afd5d1ecd0cf62eaf

WARNING: Author mismatch between patch and upstream commit:
Backport author: Pu Lehui<pulehui@huaweicloud.com>
Commit author: Liu Song<liusong@linux.alibaba.com>

Status in newer kernel trees:
6.15.y | Present (exact SHA1)
6.14.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (exact SHA1)
6.1.y | Present (exact SHA1)
5.15.y | Not found

Note: The patch differs from the upstream commit:
---
1:  877ace9eab7de ! 1:  02dd583c7ea39 arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually
    @@ Metadata
      ## Commit message ##
         arm64: spectre: increase parameters that can be used to turn off bhb mitigation individually
     
    +    [ Upstream commit 877ace9eab7de032f954533afd5d1ecd0cf62eaf ]
    +
         In our environment, it was found that the mitigation BHB has a great
         impact on the benchmark performance. For example, in the lmbench test,
         the "process fork && exit" test performance drops by 20%.
    @@ Commit message
         Acked-by: Catalin Marinas <catalin.marinas@arm.com>
         Link: https://lore.kernel.org/r/1661514050-22263-1-git-send-email-liusong@linux.alibaba.com
         Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
    +    Signed-off-by: Pu Lehui <pulehui@huawei.com>
     
      ## Documentation/admin-guide/kernel-parameters.txt ##
     @@
    - 					       spectre_v2_user=off [X86]
      					       spec_store_bypass_disable=off [X86,PPC]
    + 					       spectre_v2_user=off [X86]
      					       ssbd=force-off [ARM64]
     +					       nospectre_bhb [ARM64]
    - 					       l1tf=off [X86]
    - 					       mds=off [X86]
      					       tsx_async_abort=off [X86]
    + 
    + 				Exceptions:
     @@
      			vulnerability. System may allow data leaks with this
      			option.
      
    -+	nospectre_bhb	[ARM64] Disable all mitigations for Spectre-BHB (branch
    ++	nospectre_bhb   [ARM64] Disable all mitigations for Spectre-BHB (branch
     +			history injection) vulnerability. System may allow data leaks
     +			with this option.
     +
    @@ Documentation/admin-guide/kernel-parameters.txt
      
     
      ## arch/arm64/kernel/proton-pack.c ##
    -@@ arch/arm64/kernel/proton-pack.c: static void this_cpu_set_vectors(enum arm64_bp_harden_el1_vectors slot)
    - 	isb();
    - }
    +@@ arch/arm64/kernel/proton-pack.c: static void kvm_setup_bhb_slot(const char *hyp_vecs_start) { }
    + #endif /* CONFIG_KVM */
      
    + static bool spectre_bhb_fw_mitigated;
     +static bool __read_mostly __nospectre_bhb;
     +static int __init parse_spectre_bhb_param(char *str)
     +{
    @@ arch/arm64/kernel/proton-pack.c: static void this_cpu_set_vectors(enum arm64_bp_
     +	return 0;
     +}
     +early_param("nospectre_bhb", parse_spectre_bhb_param);
    -+
    + 
      void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
      {
    - 	bp_hardening_cb_t cpu_cb;
     @@ arch/arm64/kernel/proton-pack.c: void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
      		/* No point mitigating Spectre-BHB alone. */
      	} else if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY)) {
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |