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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
	Greg Kurz <gkurz@linux.vnet.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] mmap-alloc: use same backend for all	mappings
Date: Tue, 01 Dec 2015 16:23:11 +0530	[thread overview]
Message-ID: <878u5eqw2w.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <20151130185328-mutt-send-email-mst@redhat.com>

"Michael S. Tsirkin" <mst@redhat.com> writes:

> On Mon, Nov 30, 2015 at 02:46:31PM +0100, Greg Kurz wrote:
>> On Mon, 30 Nov 2015 15:06:33 +0200
>> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>> 


....
>> 
>> On ppc64, the address space is divided in 256MB-sized segments where all pages
>> have the same size. This is a hw limitation IIUC. I don't know if it can be
>> fixed and I'll let Ben comment on it.
>
> But it's anonymous memory with PROT_NONE.  There should be no pages there:
> just a chunk of virtual memory reserved.
>

ppc64 use page size (called as base page size) to find the hash slot in
which we find the virtual address to real address translation. All the
pages in a segment should have same base page size. Hugetlb pages have a
base page size of 16M whereas a regular linux page have 64K. mmap will
fail to map a hugetlb mapping in a segment that already have regular
pages mapped.

-aneesh

  parent reply	other threads:[~2015-12-01 10:53 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-30 10:51 [Qemu-devel] [PATCH] mmap-alloc: use same backend for all mappings Greg Kurz
2015-11-30 10:53 ` Paolo Bonzini
2015-11-30 13:12   ` Michael S. Tsirkin
2015-12-01 10:42     ` Greg Kurz
2015-12-01 10:52       ` Michael S. Tsirkin
2015-11-30 13:06 ` Michael S. Tsirkin
2015-11-30 13:46   ` Greg Kurz
2015-11-30 16:59     ` Michael S. Tsirkin
2015-12-01 10:37       ` Greg Kurz
2015-12-01 10:53       ` Aneesh Kumar K.V [this message]
2015-12-01 10:57         ` Michael S. Tsirkin
2015-12-01 12:15           ` Aneesh Kumar K.V
2015-12-01 14:25             ` Michael S. Tsirkin
2015-12-01 13:31           ` Greg Kurz
2015-12-01 14:19             ` Michael S. Tsirkin

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