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Message-ID: <bf1ad4c3-73eb-0f8f-e627-a7e0785fe903@citrix.com>
Date:   Fri, 24 Feb 2023 10:59:54 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.7.1
From:   andrew.cooper3@citrix.com
Subject: Re: [RFC PATCH v3 15/32] x86/fred: make unions for the cs and ss
 fields in struct pt_regs
Content-Language: en-GB
To:     Xin Li <xin3.li@intel.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, kvm@vger.kernel.org
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org,
        seanjc@google.com, pbonzini@redhat.com, ravi.v.shankar@intel.com
References: <20230224070145.3572-1-xin3.li@intel.com>
 <20230224070145.3572-16-xin3.li@intel.com>
In-Reply-To: <20230224070145.3572-16-xin3.li@intel.com>
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On 24/02/2023 7:01 am, Xin Li wrote:
> diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
> index f4db78b09c8f..341e44847cc1 100644
> --- a/arch/x86/include/asm/ptrace.h
> +++ b/arch/x86/include/asm/ptrace.h
> @@ -82,13 +82,41 @@ struct pt_regs {
>   * On hw interrupt, it's IRQ number:
>   */
>  	unsigned long orig_ax;
> -/* Return frame for iretq */
> +
> +	/* Return frame for iretq/eretu/erets */
>  	unsigned long ip;
> -	unsigned long cs;
> +	union {
> +		unsigned long  csl; /* CS + any fields above it */

I guess that CSL here is supposed to mean cs long, but CSL (Current
Stack Level) is a new term in the FRED spec which isn't this.

This causes changes such as the final hunk in patch 27 to read
incorrectly, despite being technically correct.

cs_slot would be much clearer in code, but tbh, even cs_l would be
better than the version without an underscore.

And obviously, whatever is done here should be mirrored for ss.

~Andrew