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Message-ID: <58bde8b7-018c-5f4c-282d-629cfb42515f@suse.com>
Date: Sat, 29 Jul 2023 10:24:54 +0300
From: Nikolay Borisov <nik.borisov@...e.com>
To: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Cc: x86@...nel.org, bp@...en8.de, tglx@...utronix.de,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/cpu/amd: Report zenbleed in sysfs
On 29.07.23 г. 2:14 ч., Pawan Gupta wrote:
> On Thu, Jul 27, 2023 at 10:54:46AM +0300, Nikolay Borisov wrote:
>> Initial submission of Zenbleed fix omitted reporting the bug in sysfs.
>> There's no reason why it shouldn't be reported so let's add it among
>> the other vulnerabilities.
>>
>> Signed-off-by: Nikolay Borisov <nik.borisov@...e.com>
>> ---
>> .../ABI/testing/sysfs-devices-system-cpu | 1 +
>> arch/x86/kernel/cpu/amd.c | 15 +++++++++++++++
>> drivers/base/cpu.c | 8 ++++++++
>> include/linux/cpu.h | 2 ++
>> 4 files changed, 26 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
>> index ecd585ca2d50..30bb4196e451 100644
>> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
>> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
>> @@ -524,6 +524,7 @@ What: /sys/devices/system/cpu/vulnerabilities
>> /sys/devices/system/cpu/vulnerabilities/itlb_multihit
>> /sys/devices/system/cpu/vulnerabilities/mmio_stale_data
>> /sys/devices/system/cpu/vulnerabilities/retbleed
>> + /sys/devices/system/cpu/vulnerabilities/zenbleed
>> Date: January 2018
>> Contact: Linux kernel mailing list <linux-kernel@...r.kernel.org>
>> Description: Information about CPU vulnerabilities
>> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
>> index 26ad7ca423e7..3ab9745eafc5 100644
>> --- a/arch/x86/kernel/cpu/amd.c
>> +++ b/arch/x86/kernel/cpu/amd.c
>> @@ -1279,6 +1279,21 @@ u32 amd_get_highest_perf(void)
>> }
>> EXPORT_SYMBOL_GPL(amd_get_highest_perf);
>>
>> +ssize_t cpu_show_zenbleed(struct device *dev, struct device_attribute *attr, char *buf)
>> +{
>> +
>
> Extra newline.
>
>> + if (!cpu_has_amd_erratum(&boot_cpu_data, amd_zenbleed) ||
>> + !boot_cpu_has(X86_FEATURE_AVX) ||
>> + boot_cpu_has(X86_FEATURE_HYPERVISOR))
>> + return sysfs_emit(buf, "Not affected\n");
>> +
>> + if (!cpu_has_zenbleed_microcode()) {
>
> For readability this can check of microcode present case, and drop the
> NOT operator.
>
>> + return sysfs_emit(buf, "Mitigation: Chickenbit\n");
>
> Shouldn't this be checking if the chicken bit is set? And if its not set
> then report "Vulnerable".
>
> But, looking at zenbleed_check() it appear that the chicken bit for
> zenbleed will always be present, and it will always be set if microcode
> is not present.
Yeah, but based on feedback I got from Boris it seems this is not going
to be merged so it doesn't matter.
>
>> + } else {
>> + return sysfs_emit(buf, "Mitigation: Microcode\n");
>> + }
>> +}
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