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From: Wei Yang <richardw.yang@linux.intel.com>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: fam@euphon.net, mst@redhat.com, mark.cave-ayland@ilande.co.uk,
	qemu-devel@nongnu.org, kraxel@redhat.com, den@openvz.org,
	qemu-block@nongnu.org, quintela@redhat.com, armbru@redhat.com,
	pasic@linux.ibm.com, borntraeger@de.ibm.com,
	marcandre.lureau@redhat.com, ehabkost@redhat.com, sw@weilnetz.de,
	dgilbert@redhat.com, yuval.shaia@oracle.com,
	alex.williamson@redhat.com, stefanha@redhat.com,
	imammedo@redhat.com, david@gibson.dropbear.id.au,
	kwolf@redhat.com, cohuck@redhat.com, qemu-s390x@nongnu.org,
	mreitz@redhat.com, qemu-ppc@nongnu.org,
	Wei Yang <richardw.yang@linux.intel.com>,
	pbonzini@redhat.com
Subject: Re: [PATCH 1/2] cpu: use ROUND_UP() to define xxx_PAGE_ALIGN
Date: Mon, 14 Oct 2019 11:19:06 +0800
Message-ID: <20191014031906.GA10129@richard> (raw)
In-Reply-To: <4036820a-f357-9e67-7e58-cbb9186d0ef4@linaro.org>

On Sun, Oct 13, 2019 at 07:38:04PM -0700, Richard Henderson wrote:
>On 10/13/19 6:01 PM, Wei Yang wrote:
>>> No, please.
>>>
>>> (1) The compiler does not know that qemu_*host_page_size is a power of 2, and
>>> will generate a real division at runtime.  The same is true for
>>> TARGET_PAGE_SIZE when TARGET_PAGE_BITS_VARY.
>>>
>> 
>> Confused
>> 
>> The definition of ROUND_UP is:
>> 
>> #define ROUND_UP(n, d) (((n) + (d) - 1) & -(0 ? (n) : (d)))
>
>Ah, my bad, I did confuse this with QEMU_ALIGN_UP.
>
>Hmm.
>
>	lea	-1(n, size), t
>	neg	size
>	and	size, t
>
>vs
>
>	mov	mask, t
>	not	t
>	add	n, t
>	and	mask, t
>
>which is what I proposed here
>
>>> https://lists.gnu.org/archive/html/qemu-devel/2019-09/msg04526.html
>
>I'm ok with your version.
>
>Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>

Thanks for your clarification.

Have a nice day

>
>r~
>

-- 
Wei Yang
Help you, Help me


  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-13  2:11 [PATCH 0/2] cleanup on page size Wei Yang
2019-10-13  2:11 ` [PATCH 1/2] cpu: use ROUND_UP() to define xxx_PAGE_ALIGN Wei Yang
2019-10-13  6:34   ` Michael S. Tsirkin
2019-10-13  9:27   ` David Gibson
2019-10-13 15:56   ` Richard Henderson
2019-10-13 23:36     ` David Gibson
2019-10-14  1:01     ` Wei Yang
2019-10-14  2:38       ` Richard Henderson
2019-10-14  3:19         ` Wei Yang [this message]
2019-10-14 16:25   ` Juan Quintela
2019-10-13  2:11 ` [PATCH 2/2] core: replace getpagesize() with qemu_real_host_page_size Wei Yang
2019-10-13  6:35   ` Michael S. Tsirkin
2019-10-13  9:28   ` David Gibson
2019-10-16  1:25     ` Wei Yang
2019-10-13 16:03   ` Richard Henderson
2019-10-14  9:15   ` Dr. David Alan Gilbert
2019-10-14 21:36     ` Wei Yang
2019-10-14 23:12       ` Richard Henderson
2019-10-15 11:45   ` Yuval Shaia
2019-10-16  1:07     ` Wei Yang
2019-10-23  9:19   ` Paolo Bonzini
2019-10-13  6:36 ` [PATCH 0/2] cleanup on page size Michael S. Tsirkin
2019-10-14 21:59 ` Wei Yang

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