linux-kernel - Re: [PATCH v3 1/3] arm64: errata: Assume that unknown CPUs _are

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: <CAD=FV=U6t42VNFSY3Jk1XUk+O=B8VnhioQxOHMv86ZH0BqLJQQ@mail.gmail.com>
Date: Mon, 6 Jan 2025 14:32:52 -0800
From: Doug Anderson <dianders@...omium.org>
To: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Mark Rutland <mark.rutland@....com>
Cc: Roxana Bradescu <roxabee@...gle.com>, Julius Werner <jwerner@...omium.org>, 
	bjorn.andersson@....qualcomm.com, linux-arm-kernel@...ts.infradead.org, 
	linux-arm-msm@...r.kernel.org, Jeffrey Hugo <quic_jhugo@...cinc.com>, 
	Trilok Soni <quic_tsoni@...cinc.com>, stable@...r.kernel.org, 
	James Morse <james.morse@....com>, Kent Overstreet <kent.overstreet@...ux.dev>, 
	Suren Baghdasaryan <surenb@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] arm64: errata: Assume that unknown CPUs _are_
 vulnerable to Spectre BHB

Hi,

On Thu, Dec 19, 2024 at 12:54 PM Douglas Anderson <dianders@...omium.org> wrote:
>
> @@ -916,9 +932,8 @@ static enum mitigation_state spectre_bhb_get_cpu_fw_mitigation_state(void)
>         }
>  }
>
> -static bool is_spectre_bhb_fw_affected(int scope)
> +static bool is_spectre_bhb_fw_affected(void)
>  {
> -       static bool system_affected;
>         enum mitigation_state fw_state;
>         bool has_smccc = arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_NONE;
>         static const struct midr_range spectre_bhb_firmware_mitigated_list[] = {
> @@ -929,16 +944,8 @@ static bool is_spectre_bhb_fw_affected(int scope)
>         bool cpu_in_list = is_midr_in_range_list(read_cpuid_id(),
>                                          spectre_bhb_firmware_mitigated_list);
>
> -       if (scope != SCOPE_LOCAL_CPU)
> -               return system_affected;
> -
>         fw_state = spectre_bhb_get_cpu_fw_mitigation_state();
> -       if (cpu_in_list || (has_smccc && fw_state == SPECTRE_MITIGATED)) {
> -               system_affected = true;
> -               return true;
> -       }
> -
> -       return false;
> +       return cpu_in_list || (has_smccc && fw_state == SPECTRE_MITIGATED);

Upon looking at this again, I realized that I can fully get rid of
`cpu_in_list` here and the whole `spectre_bhb_firmware_mitigated_list`
variable. After my patch there's only one caller to this function and
it only cares whether the firmware call can be used to mitigate, so I
can rename this function to has_spectre_bhb_fw_mitigation() and
simplify it and the caller.

I'll plan to spin this in the next day or two and also include the
proper loop value for Kryo-400 cores, since I've got that now.

I'll plan to keep Julius's review tag unless told not to.

-Doug