Re: [Xen-devel] [PATCH] ns16550: Re-order the serial port address checking

From: Julien Grall <julien@xen.org>
To: Wei Xu <xuwei5@hisilicon.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	"Zengtao \(B\)" <prime.zeng@hisilicon.com>, Wei Liu <wl@xen.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	Linuxarm <linuxarm@huawei.com>,
	Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
	Jan Beulich <jbeulich@suse.com>
Subject: Re: [Xen-devel] [PATCH] ns16550: Re-order the serial port address checking
Date: Mon, 24 Feb 2020 22:03:39 +0000	[thread overview]
Message-ID: <8bb7d100-0ca4-c0f9-b294-f2e7a173e1c9@xen.org> (raw)
In-Reply-To: <5E53B3E3.6070304@hisilicon.com>

Hi Wei,

Thank you for sending a follow-up.

On 24/02/2020 11:30, Wei Xu wrote:
> Check the serial port address space before checking the address.

Could you explain in a sentence why you want to re-order?

Cheers,

> 
> Signed-off-by: Wei Xu <xuwei5@hisilicon.com>
> ---
>   xen/drivers/char/ns16550.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
> index dc8ac4c..425e044 100644
> --- a/xen/drivers/char/ns16550.c
> +++ b/xen/drivers/char/ns16550.c
> @@ -1644,6 +1644,12 @@ static int __init ns16550_acpi_uart_init(const void *data)
> 
>       spcr = container_of(table, struct acpi_table_spcr, header);
> 
> +    if ( unlikely(spcr->serial_port.space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) )
> +    {
> +        printk("ns16550: Address space type is not mmio\n");
> +        return -EINVAL;
> +    }
> +
>       /*
>        * The serial port address may be 0 for example
>        * if the console redirection is disabled.
> @@ -1654,12 +1660,6 @@ static int __init ns16550_acpi_uart_init(const void *data)
>           return -EINVAL;
>       }
> 
> -    if ( unlikely(spcr->serial_port.space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) )
> -    {
> -        printk("ns16550: Address space type is not mmio\n");
> -        return -EINVAL;
> -    }
> -
>       ns16550_init_common(uart);
> 
>       /*
> 

-- 
Julien Grall

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