From: Alexander Graf <agraf@suse.de>
To: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
Cc: linux-arch@vger.kernel.org, x86@kernel.org, arnd@arndb.de,
kvm@vger.kernel.org, kvm-ia64@vger.kernel.org,
fernando@oss.ntt.co.jp, mtosatti@redhat.com,
linux-kernel@vger.kernel.org, kvm-ppc@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 7/12 not tested yet] PPC: introduce __set_bit() like function for bitmaps in user space
Date: Tue, 11 May 2010 18:00:42 +0200 [thread overview]
Message-ID: <4BE97F2A.5080900@suse.de> (raw)
In-Reply-To: <20100504220418.083929bc.takuya.yoshikawa@gmail.com>
Takuya Yoshikawa wrote:
> During the work of KVM's dirty page logging optimization, we encountered
> the need of manipulating bitmaps in user space efficiantly. To achive this,
> we introduce a uaccess function for setting a bit in user space following
> Avi's suggestion.
>
> KVM is now using dirty bitmaps for live-migration and VGA. Although we need
> to update them from kernel side, copying them every time for updating the
> dirty log is a big bottleneck. Especially, we tested that zero-copy bitmap
> manipulation improves responses of GUI manipulations a lot.
>
> We also found one similar need in drivers/vhost/vhost.c in which the author
> implemented set_bit_to_user() locally using inefficient functions: see TODO
> at the top of that.
>
> Probably, this kind of need would be common for virtualization area.
>
> So we introduce a function set_bit_user_non_atomic().
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
> CC: Alexander Graf <agraf@suse.de>
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> ---
> arch/powerpc/include/asm/uaccess.h | 19 +++++++++++++++++++
> 1 files changed, 19 insertions(+), 0 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 3a01ce8..f878326 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -321,6 +321,25 @@ do { \
> __gu_err; \
> })
>
> +static inline int set_bit_user_non_atomic(int nr, void __user *addr)
> +{
> + u8 __user *p;
> + u8 val;
> +
> + p = (u8 __user *)((unsigned long)addr + nr / BITS_PER_BYTE);
>
Does C do the + or the / first? Either way, I'd like to see brackets here :)
Alex
next prev parent reply other threads:[~2010-05-11 16:00 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 [this message]
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
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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