From: Arnd Bergmann <arnd@arndb.de>
To: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
Cc: linux-arch@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org,
kvm-ia64@vger.kernel.org, fernando@oss.ntt.co.jp,
mtosatti@redhat.com, agraf@suse.de, kvm-ppc@vger.kernel.org,
linux-kernel@vger.kernel.org, yoshikawa.takuya@oss.ntt.co.jp,
linuxppc-dev@ozlabs.org, mingo@redhat.com, paulus@samba.org,
avi@redhat.com, hpa@zytor.com, tglx@linutronix.de
Subject: Re: [RFC][PATCH resend 8/12] asm-generic: bitops: introduce le bit offset macro
Date: Tue, 4 May 2010 17:03:00 +0200 [thread overview]
Message-ID: <201005041703.00549.arnd@arndb.de> (raw)
In-Reply-To: <20100504220500.7695cd66.takuya.yoshikawa@gmail.com>
On Tuesday 04 May 2010, Takuya Yoshikawa wrote:
>
> Although we can use *_le_bit() helpers to treat bitmaps le arranged,
> having le bit offset calculation as a seperate macro gives us more freedom.
>
> For example, KVM has le arranged dirty bitmaps for VGA, live-migration
> and they are used in user space too. To avoid bitmap copies between kernel
> and user space, we want to update the bitmaps in user space directly.
> To achive this, le bit offset with *_user() functions help us a lot.
>
> So let us use the le bit offset calculation part by defining it as a new
> macro: generic_le_bit_offset() .
Does this work correctly if your user space is 32 bits (i.e. unsigned long
is different size in user space and kernel) in both big- and little-endian
systems?
I'm not sure about all the details, but I think you cannot in general share
bitmaps between user space and kernel because of this.
Arnd
next prev parent reply other threads:[~2010-05-04 15:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-04 12:56 [RFC][PATCH 0/12] KVM, x86, ppc, asm-generic: moving dirty bitmaps to user space Takuya Yoshikawa
2010-05-04 12:58 ` [RFC][PATCH 1/12 applied today] KVM: x86: avoid unnecessary bitmap allocation when memslot is clean Takuya Yoshikawa
2010-05-04 13:00 ` [RFC][PATCH 2/12] KVM: introduce slot level dirty state management Takuya Yoshikawa
2010-05-04 13:01 ` [RFC][PATCH 3/12] KVM: introduce wrapper functions to create and destroy dirty bitmaps Takuya Yoshikawa
2010-05-04 13:02 ` [RFC][PATCH 4/12] x86: introduce copy_in_user() for 32-bit Takuya Yoshikawa
2010-05-04 13:02 ` [RFC][PATCH 5/12] x86: introduce __set_bit() like function for bitmaps in user space Takuya Yoshikawa
2010-05-04 13:03 ` [RFC][PATCH 6/12 not tested yet] PPC: introduce copy_in_user() for 32-bit Takuya Yoshikawa
2010-05-04 13:04 ` [RFC][PATCH 7/12 not tested yet] PPC: introduce __set_bit() like function for bitmaps in user space Takuya Yoshikawa
2010-05-11 16:00 ` Alexander Graf
2010-05-12 9:25 ` Takuya Yoshikawa
2010-05-04 13:05 ` [RFC][PATCH resend 8/12] asm-generic: bitops: introduce le bit offset macro Takuya Yoshikawa
2010-05-04 15:03 ` Arnd Bergmann [this message]
2010-05-04 16:08 ` Avi Kivity
2010-05-05 2:59 ` Takuya Yoshikawa
2010-05-06 13:38 ` Arnd Bergmann
2010-05-10 11:46 ` Takuya Yoshikawa
2010-05-10 12:01 ` Avi Kivity
2010-05-10 12:01 ` Arnd Bergmann
2010-05-10 12:09 ` Takuya Yoshikawa
2010-05-04 13:06 ` [RFC][PATCH 9/12] KVM: introduce a wrapper function of set_bit_user_non_atomic() Takuya Yoshikawa
2010-05-04 13:07 ` [RFC][PATCH RFC 10/12] KVM: move dirty bitmaps to user space Takuya Yoshikawa
2010-05-11 3:28 ` Marcelo Tosatti
2010-05-12 6:27 ` Takuya Yoshikawa
2010-05-04 13:08 ` [RFC][PATCH 11/12] KVM: introduce new API for getting/switching dirty bitmaps Takuya Yoshikawa
2010-05-11 3:43 ` Marcelo Tosatti
2010-05-11 5:53 ` Takuya Yoshikawa
2010-05-11 14:07 ` Marcelo Tosatti
2010-05-12 6:03 ` Takuya Yoshikawa
2010-05-04 13:11 ` [RFC][PATCH 12/12 sample] qemu-kvm: use " Takuya Yoshikawa
2010-05-10 12:06 ` [RFC][PATCH 0/12] KVM, x86, ppc, asm-generic: moving dirty bitmaps to user space Avi Kivity
2010-05-10 12:26 ` Takuya Yoshikawa
2010-05-11 10:11 ` Takuya Yoshikawa
2010-05-13 11:47 ` Avi Kivity
2010-05-17 9:06 ` Takuya Yoshikawa
2010-05-11 15:55 ` Alexander Graf
2010-05-12 9:19 ` Takuya Yoshikawa
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