linux-kernel - Re: [PATCH RFC 06/13] x86/irq: Unionize PID.PIR for 64bit access w/o casting

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Message-ID: <87lea7uvev.ffs@tglx>
Date:   Wed, 06 Dec 2023 17:51:04 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 Kernel <x86@...nel.org>,
        iommu@...ts.linux.dev, Lu Baolu <baolu.lu@...ux.intel.com>,
        kvm@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, maz@...nel.org,
        peterz@...radead.org, seanjc@...gle.com,
        Robin Murphy <robin.murphy@....com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH RFC 06/13] x86/irq: Unionize PID.PIR for 64bit access
 w/o casting

On Sat, Nov 11 2023 at 20:16, Jacob Pan wrote:
> Make PIR field into u64 such that atomic xchg64 can be used without ugly
> casting.

Make PIR field into... That's not a sentence.


> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>  arch/x86/include/asm/posted_intr.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/posted_intr.h b/arch/x86/include/asm/posted_intr.h
> index 2cd9ac1af835..3af00f5395e4 100644
> --- a/arch/x86/include/asm/posted_intr.h
> +++ b/arch/x86/include/asm/posted_intr.h
> @@ -9,7 +9,10 @@
>  
>  /* Posted-Interrupt Descriptor */
>  struct pi_desc {
> -	u32 pir[8];     /* Posted interrupt requested */
> +	union {
> +		u32 pir[8];     /* Posted interrupt requested */
> +		u64 pir_l[4];

pir_l is really not intuitive. What's wrong with spelling the type out
in the name: pir64[4] ?

> +	};
>  	union {
>  		struct {
>  				/* bit 256 - Outstanding Notification */