linux-kernel - Re: the x86 sysret_rip test fails on the Intel FRED architecture

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Message-ID: <b6e36a5c-6f5e-eda6-54ad-a0c20eb00402@intel.com>
Date:   Sat, 21 Jan 2023 20:34:09 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Li, Xin3" <xin3.li@...el.com>, "H. Peter Anvin" <hpa@...or.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: the x86 sysret_rip test fails on the Intel FRED architecture

On 1/21/23 19:38, Li, Xin3 wrote:
>> However, it doesn't seem to make sense to do so to me. The current behavior is
>> much more of an artifact than desired behavior.
> We kind of have an agreement that %r11 = %flags after returning from the kernel.
> 
> And the question is, is it what we want?

Can the selftest just set r11=rflags before the syscall?  The old
syscall entry path will set r11=rflags.  The FRED path won't touch it.
Either case will pass an r11==rflags check.