Re: [RFC PATCH 04/13] x86/fpu/xstate: Enumerate User Interrupts supervisor state

From: Thomas Gleixner <tglx@linutronix.de>
To: Sohil Mehta <sohil.mehta@intel.com>, x86@kernel.org
Cc: Sohil Mehta <sohil.mehta@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@kernel.org>, Jens Axboe <axboe@kernel.dk>,
	Christian Brauner <christian@brauner.io>,
	Peter Zijlstra <peterz@infradead.org>,
	Shuah Khan <shuah@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Jonathan Corbet <corbet@lwn.net>, Ashok Raj <ashok.raj@intel.com>,
	Jacob Pan <jacob.jun.pan@linux.intel.com>,
	Gayatri Kammela <gayatri.kammela@intel.com>,
	Zeng Guang <guang.zeng@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Randy E Witt <randy.e.witt@intel.com>,
	Ravi V Shankar <ravi.v.shankar@intel.com>,
	Ramesh Thomas <ramesh.thomas@intel.com>,
	linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [RFC PATCH 04/13] x86/fpu/xstate: Enumerate User Interrupts supervisor state
Date: Fri, 24 Sep 2021 00:34:04 +0200	[thread overview]
Message-ID: <87ilyqgbvn.ffs@tglx> (raw)
In-Reply-To: <20210913200132.3396598-5-sohil.mehta@intel.com>

On Mon, Sep 13 2021 at 13:01, Sohil Mehta wrote:
> Enable xstate supervisor support for User Interrupts by default.

What means enabled by default? It's enabled when available and not
disabled on the command line.

> The user interrupt state for a task consists of the MSR state and the
> User Interrupt Flag (UIF) value. XSAVES and XRSTORS handle saving and
> restoring both of these states.
>
> <The supervisor XSTATE code might be reworked based on issues reported
> in the past. The Uintr context switching code would also need rework and
> additional testing in that regard.>

What? Which issues were reported and if they have been reported then how
is the provided code correct?

> +/*
> + * State component 14 is supervisor state used for User Interrupts state.
> + * The size of this state is 48 bytes
> + */
> +struct uintr_state {
> +	u64 handler;
> +	u64 stack_adjust;
> +	u32 uitt_size;
> +	u8  uinv;
> +	u8  pad1;
> +	u8  pad2;
> +	u8  uif_pad3;		/* bit 7 - UIF, bits 6:0 - reserved */

Please do not use tail comments. Also what kind of name is uif_pad3?
Bitfields exist for a reason.

Aside of that please use tabs to seperate type and name.

> +	u64 upid_addr;
> +	u64 uirr;
> +	u64 uitt_addr;
> +} __packed;
> +

Thanks,

        tglx