linux-kernel - RE: [PATCH v4 7/7] ACPI / x86: introduce acpi_os

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Date:	Thu, 24 Dec 2015 07:57:34 +0000
From:	"Chen, Yu C" <yu.c.chen@...el.com>
To:	Andy Lutomirski <luto@...capital.net>,
	"Zheng, Lv" <lv.zheng@...el.com>
CC:	"Moore, Robert" <robert.moore@...el.com>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	"Brown, Len" <len.brown@...el.com>,
	"Andy Lutomirski" <luto@...nel.org>, Lv Zheng <zetalog@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, "Borislav Petkov" <bp@...en8.de>
Subject: RE: [PATCH v4 7/7] ACPI / x86: introduce acpi_os_readable() support

Hi,Andy

> -----Original Message-----
> From: Andy Lutomirski [mailto:luto@...capital.net]
> Sent: Thursday, December 24, 2015 9:40 AM
> To: Zheng, Lv
> Cc: Chen, Yu C; Moore, Robert; Wysocki, Rafael J; Brown, Len; Andy
> Lutomirski; Lv Zheng; linux-kernel@...r.kernel.org; Linux ACPI; H. Peter
> Anvin; Borislav Petkov
> Subject: Re: [PATCH v4 7/7] ACPI / x86: introduce acpi_os_readable() support
> 
> On Tue, Dec 22, 2015 at 7:25 PM, Zheng, Lv <lv.zheng@...el.com> wrote:
[cut]
> 
> It seems a bit unfortunate to me that the ACPICA debugger lets userspace
> choose what address to dump rather than dumping by pathname, but given
> that constraint, I guess this function is needed.
> 
> Can you do something like checking virt_addr_valid and then using
> virt_to_pfn and page_is_ram?  If that's not enough (e.g. if it doesn't work for
> vmalloc addresses and you need those), you could try to do something like
> slow_virt_to_phys, but you'd need to do some extra checks to avoid the
> BUG in the function.
> 
[Yu] This is a  good method,  firstly virt_addr_valid can  exclude the vaddr of vmalloc/kmap
, then slow_virt_to_phys can check if this vaddr has a valid pte physical address, but I guess
we need another non-BUG_on version of slow_virt_to_phys,  I'll try to test with your suggestion,
thanks!
Yu