linux-kernel - Re: [PATCH v1 2/8] x86/xen: simplify xen_oldmem_pfn_is

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Date:   Tue, 28 Sep 2021 20:59:36 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...e.de>,
        Mike Rapoport <rppt@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, x86@...nel.org,
        xen-devel@...ts.xenproject.org,
        virtualization@...ts.linux-foundation.org,
        kexec@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v1 2/8] x86/xen: simplify xen_oldmem_pfn_is_ram()


On 9/28/21 2:22 PM, David Hildenbrand wrote:
> Let's simplify return handling.
>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/x86/xen/mmu_hvm.c | 11 ++---------
>  1 file changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/xen/mmu_hvm.c b/arch/x86/xen/mmu_hvm.c
> index b242d1f4b426..eb61622df75b 100644
> --- a/arch/x86/xen/mmu_hvm.c
> +++ b/arch/x86/xen/mmu_hvm.c
> @@ -21,23 +21,16 @@ static int xen_oldmem_pfn_is_ram(unsigned long pfn)
>  		.domid = DOMID_SELF,
>  		.pfn = pfn,
>  	};
> -	int ram;
>  
>  	if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a))
>  		return -ENXIO;
>  
>  	switch (a.mem_type) {
>  	case HVMMEM_mmio_dm:
> -		ram = 0;
> -		break;
> -	case HVMMEM_ram_rw:
> -	case HVMMEM_ram_ro:
> +		return 0;
>  	default:
> -		ram = 1;
> -		break;
> +		return 1;
>  	}
> -
> -	return ram;
>  }
>  #endif
>  


How about

    return a.mem_type != HVMMEM_mmio_dm;


Result should be promoted to int and this has added benefit of not requiring changes in patch 4.


-boris