From: Baoquan He <bhe@redhat.com>
To: Chao Fan <fanc.fnst@cn.fujitsu.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
x86@kernel.org, linux-kernel@vger.kernel.org,
keescook@chromium.org, n-horiguchi@ah.jp.nec.com,
indou.takao@jp.fujitsu.com, caoj.fnst@cn.fujitsu.com,
douly.fnst@cn.fujitsu.com
Subject: Re: [PATCH v5 4/4] x86/boot/KASLR: Limit kaslr to choosing the immovable memory
Date: Mon, 27 Aug 2018 15:01:09 +0800 [thread overview]
Message-ID: <20180827070109.GD1748@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20180827062854.GD6769@localhost.localdomain>
On 08/27/18 at 02:28pm, Chao Fan wrote:
> >Is it possible to take num_immovable_mem definition out from #ifdef
> >CONFIG_MEMORY_HOTREMOVE block and check it here like below? This way,
> >one level of indentation can be reduced in the for loop, and code is
> >more readable.
> >
>
> I think there is a mistake.
>
> The logical is:
> if (#ifdef CONFIG_MEMORY_HOTREMOVE) && (num_immovable_mem > 0)
> then A;
> else
> then B;
>
> But below is:
> if (num_immovable_mem > 0)
> then B;
> else if (#ifdef CONFIG_MEMORY_HOTREMOVE)
> then A;
> else
> nothing;
>
> The precondition of the loop is (num_immovable_mem > 0), because
> there is only one condition that we need go the A code:
> CONFIG_MEMORY_HOTREMOVE is defined, and memory information in srat
> found.
Yes, we are saying the same thing. if num_immovable_mem == 0, it covers
all the cases you listed at below. Here I assume you have taken
num_immovable_mem definition out.
#ifdef CONFIG_MEMORY_HOTREMOVE
/* Store the immovable memory regions */
static struct mem_vector immovable_mem[MAX_NUMNODES*2];
#endif
/* Store the amount of immovable memory regions */
static int num_immovable_mem;
>
> But there is many conditions we go the B code:
> 1. CONFIG_MEMORY_HOTREMOVE is not defined.
> 2. CONFIG_MEMORY_HOTREMOVE defined, but we didn't get the right acpi tables
> 3. CONFIG_MEMORY_HOTREMOVE defined, or there is only one node in this machine.
>
> Yes, the code is hard to read, but you have changed the logical, there
> is a compromise method, I don't know whether is better:
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> if (num_immovable_mem == 0)
> goto B;
>
> for (i = 0; i < num_immovable_mem; i++) {
> ...
> }
> #endif
>
> B:
> slots_count(region, minimum, image_size);
>
> if (slot_area_index == MAX_SLOT_AREA) {
> debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
> return 1;
> }
> return 0;
>
>
> >
> >static bool process_mem_region(struct mem_vector *region,
> > unsigned long long minimum,
> > unsigned long long image_size)
> >{
> >
> > /*
> > * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
> > * walk all the regions, so use region directely.
> > */
> > if (num_immovable_mem > 0) {
> > slots_count(region, minimum, image_size);
> >
> > if (slot_area_index == MAX_SLOT_AREA) {
> > debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
> > return 1;
> > }
> > return 0;
> > }
> >
> >#ifdef CONFIG_MEMORY_HOTREMOVE
> > for (i = 0; i < num_immovable_mem; i++) {
> > ...
> > }
> >#endif
> >}
> >
>
>
next prev parent reply other threads:[~2018-08-27 7:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-07 6:49 [PATCH v5 0/4] x86/boot/KASLR: Parse ACPI table and limit kaslr in immovable memory Chao Fan
2018-08-07 6:49 ` [PATCH v5 1/4] x86/boot: Add acpitb.h to help parse acpi tables Chao Fan
2018-08-07 6:49 ` [PATCH v5 2/4] x86/boot: Add acpitb.c to " Chao Fan
2018-08-27 9:32 ` Baoquan He
2018-08-07 6:49 ` [PATCH v5 3/4] x86/boot/KASLR: Walk srat tables to filter immovable memory Chao Fan
2018-08-23 7:25 ` Baoquan He
2018-08-23 7:30 ` Chao Fan
2018-08-27 2:13 ` Baoquan He
2018-08-27 2:56 ` Chao Fan
2018-08-27 3:07 ` Baoquan He
2018-08-07 6:50 ` [PATCH v5 4/4] x86/boot/KASLR: Limit kaslr to choosing the " Chao Fan
2018-08-27 5:35 ` Baoquan He
2018-08-27 6:04 ` Baoquan He
2018-08-27 5:56 ` Baoquan He
2018-08-27 6:28 ` Chao Fan
2018-08-27 6:31 ` Chao Fan
2018-08-27 7:01 ` Baoquan He [this message]
2018-08-27 7:10 ` Baoquan He
2018-08-23 1:37 ` [PATCH v5 0/4] x86/boot/KASLR: Parse ACPI table and limit kaslr in " Chao Fan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180827070109.GD1748@MiWiFi-R3L-srv \
--to=bhe@redhat.com \
--cc=caoj.fnst@cn.fujitsu.com \
--cc=douly.fnst@cn.fujitsu.com \
--cc=fanc.fnst@cn.fujitsu.com \
--cc=hpa@zytor.com \
--cc=indou.takao@jp.fujitsu.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=n-horiguchi@ah.jp.nec.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).