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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Rs747sjIOcgl2qwE3tjiruNHopsRa+DcsP84kNNdDKLx282s3t+/nTq5bUrs5Gdam JUnZTH1YCedeLjbIy9v+2TS9ZVA/6rxs6PKqu/Q4IgtUXggk6RGDltHBfm3ERRZGuB hol4cScDo2puAko1FMN0q9pNmlmTbnCPOk6ibMzQ2CzS7FgKwrZBUylFkgemtaQXDu d4O1Q/8FcpgJTkvyoyXaa8YQ773+Muhkyw4Fb9uixpv89l7MwqTYXJTIybu3wnFye3 w7axg9S9JnrZ6YmPddUSJJlhzOoxrFEN99k4SgNX66rzB8EnnClIjRpatQZt2aQ3rL iI+4dC2T4F4WA== Message-ID: <0f8a5e47-58e8-4adb-a796-f31f8d35f487@zytor.com> Date: Sun, 7 Jul 2024 10:42:16 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/4] x86/fred: Parse cmdline param "fred=" in cpu_parse_early_param() To: Nikolay Borisov , linux-kernel@vger.kernel.org Cc: hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, houwenlong.hwl@antgroup.com References: <20240703085426.274801-1-xin@zytor.com> <20240703085426.274801-2-xin@zytor.com> <48e5f704-c683-43ca-bb5e-0fb691eab4d5@suse.com> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 7/4/2024 4:20 AM, Nikolay Borisov wrote: > > > On 3.07.24 г. 11:54 ч., Xin Li (Intel) wrote: >> Depending on whether FRED will be used, sysvec_install() installs >> a system interrupt handler into FRED system vector dispatch table >> or IDT.  However FRED can be disabled later in trap_init(), after >> sysvec_install() is called.  E.g., the HYPERVISOR_CALLBACK_VECTOR >> handler is registered with sysvec_install() in kvm_guest_init(), >> which is called in setup_arch() but way before trap_init().  IOW, >> there is a gap between FRED is available and available but disabled. >> As a result, when FRED is available but disabled, its IDT handler >> is not installed thus spurious_interrupt() will be invoked. >> >> Fix it by parsing cmdline param "fred=" in cpu_parse_early_param() >> to minimize the gap between FRED is available and available but >> disabled. >> >> Fixes: 3810da12710a ("x86/fred: Add a fred= cmdline param") >> Reported-by: Hou Wenlong >> Suggested-by: Thomas Gleixner >> Signed-off-by: Xin Li (Intel) >> --- >>   arch/x86/kernel/cpu/common.c |  5 +++++ >>   arch/x86/kernel/traps.c      | 26 -------------------------- >>   2 files changed, 5 insertions(+), 26 deletions(-) >> >> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c >> index d4e539d4e158..9a904fe7c829 100644 >> --- a/arch/x86/kernel/cpu/common.c >> +++ b/arch/x86/kernel/cpu/common.c >> @@ -1510,6 +1510,11 @@ static void __init cpu_parse_early_param(void) >>       if (cmdline_find_option_bool(boot_command_line, "nousershstk")) >>           setup_clear_cpu_cap(X86_FEATURE_USER_SHSTK); >> +    /* Minimize the gap between FRED is available and available but >> disabled. */ >> +    arglen = cmdline_find_option(boot_command_line, "fred", arg, >> sizeof(arg)); >> +    if (arglen != strlen("on") || strcmp(arg, "on")) > > > Just make this check : > > ret = cmdline_find_option(...) > if (ret < 0 || strcmp())) > > A lot more straightforward > I'd do if (arglen != 2 || strncmp(arg, "on", 2)) If arglen is 2, strncmp(arg, "on", 2) is essentially strcmp(arg, "on"), but I should've kept using strncmp.