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From: Andrew Cooper <amc96@srcf.net>
To: Jan Beulich <jbeulich@suse.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>, "Wei Liu" <wl@xen.org>,
	Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 3/8] x86/boot: Fix data placement around __high_start()
Date: Thu, 2 Dec 2021 14:06:56 +0000	[thread overview]
Message-ID: <923d2203-e832-3fe3-a670-530622a39ab3@srcf.net> (raw)
In-Reply-To: <4615dde8-fe24-020d-0432-6935e9c0c9fa@suse.com>

On 02/12/2021 11:49, Jan Beulich wrote:
> On 30.11.2021 11:04, Andrew Cooper wrote:
>> multiboot_ptr should be in __initdata - it is only used on the BSP path.
>> Furthermore, the .align 8 then .long means that stack_start is misaligned.
>>
>> Move both into setup.c, which lets the compiler handle the details correctly,
>> as well as providling proper debug information for them.
>>
>> Declare stack_start in setup.h and avoid extern-ing it locally in smpboot.c.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Reviewed-by: Jan Beulich <jbeulich@suse.com>

Thanks.

> Nevertheless I'd like to state that defining a variable in C when all
> its uses are in assembly seems a little odd to me.

I don't see it as odd, although I admit that I did try to see if I could
remove multiboot_ptr entirely first.  Xen is after all a single
freestanding binary.

Having the debug information (well - at a minimum, ELF size info) is
important for livepatch binary diffing, and nothing in asm by default
gets any of that.

Letting the compiler do this all for us is physically shorter, and less
prone to errors.

~Andrew


  reply	other threads:[~2021-12-02 14:07 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-30 10:04 [PATCH 0/8] x86: Support for __ro_after_init Andrew Cooper
2021-11-30 10:04 ` [PATCH 1/8] x86/boot: Drop incorrect mapping at l2_xenmap[0] Andrew Cooper
2021-11-30 10:33   ` Jan Beulich
2021-11-30 11:14     ` Andrew Cooper
2021-11-30 11:22       ` Jan Beulich
2021-11-30 12:39         ` Andrew Cooper
2021-11-30 10:04 ` [PATCH 2/8] x86/boot: Better describe the pagetable relocation loops Andrew Cooper
2021-12-02 11:43   ` Jan Beulich
2021-11-30 10:04 ` [PATCH 3/8] x86/boot: Fix data placement around __high_start() Andrew Cooper
2021-12-02 11:49   ` Jan Beulich
2021-12-02 14:06     ` Andrew Cooper [this message]
2021-11-30 10:04 ` [PATCH 4/8] x86/mm: Drop bogus cacheability logic in update_xen_mappings() Andrew Cooper
2021-11-30 13:11   ` Andrew Cooper
2021-11-30 14:56     ` Andrew Cooper
2021-11-30 10:04 ` [PATCH 5/8] x86/boot: Drop xen_virt_end Andrew Cooper
2021-12-02 11:56   ` Jan Beulich
2021-12-02 14:07     ` Andrew Cooper
2021-11-30 10:04 ` [PATCH 6/8] x86/boot: Adjust .text/.rodata/etc permissions in one place Andrew Cooper
2021-12-02 12:15   ` Jan Beulich
2021-11-30 10:04 ` [PATCH 7/8] x86/boot: Support __ro_after_init Andrew Cooper
2021-12-02 13:10   ` Jan Beulich
2021-11-30 10:04 ` [PATCH RFC 8/8] x86/boot: Check that permission restrictions have taken effect Andrew Cooper
2021-12-02 13:33   ` Jan Beulich
2021-12-06 18:12     ` Andrew Cooper

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