From: Gregory Haskins <ghaskins@novell.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, agraf@suse.de,
pmullaney@novell.com, pmorreale@novell.com,
anthony@codemonkey.ws, rusty@rustcorp.com.au,
netdev@vger.kernel.org, kvm@vger.kernel.org, avi@redhat.com,
bhutchings@solarflare.com, andi@firstfloor.org, gregkh@suse.de,
herber@gondor.apana.org.au, chrisw@sous-sol.org,
shemminger@vyatta.com
Subject: Re: [RFC PATCH v2 03/19] vbus: add connection-client helper infrastructure
Date: Thu, 04 Jun 2009 14:18:10 -0400 [thread overview]
Message-ID: <4A280FE2.2090101@novell.com> (raw)
In-Reply-To: <20090604180611.GA16387@redhat.com>
[-- Attachment #1: Type: text/plain, Size: 2301 bytes --]
Michael S. Tsirkin wrote:
> On Thu, Apr 09, 2009 at 12:30:57PM -0400, Gregory Haskins wrote:
>
>> +static unsigned long
>> +task_memctx_copy_to(struct vbus_memctx *ctx, void *dst, const void *src,
>> + unsigned long n)
>> +{
>> + struct task_memctx *tm = to_task_memctx(ctx);
>> + struct task_struct *p = tm->task;
>> +
>> + while (n) {
>> + unsigned long offset = ((unsigned long)dst)%PAGE_SIZE;
>> + unsigned long len = PAGE_SIZE - offset;
>> + int ret;
>> + struct page *pg;
>> + void *maddr;
>> +
>> + if (len > n)
>> + len = n;
>> +
>> + down_read(&p->mm->mmap_sem);
>> + ret = get_user_pages(p, p->mm,
>> + (unsigned long)dst, 1, 1, 0, &pg, NULL);
>> +
>> + if (ret != 1) {
>> + up_read(&p->mm->mmap_sem);
>> + break;
>> + }
>> +
>> + maddr = kmap_atomic(pg, KM_USER0);
>> + memcpy(maddr + offset, src, len);
>> + kunmap_atomic(maddr, KM_USER0);
>> + set_page_dirty_lock(pg);
>> + put_page(pg);
>> + up_read(&p->mm->mmap_sem);
>> +
>> + src += len;
>> + dst += len;
>> + n -= len;
>> + }
>> +
>> + return n;
>> +}
>>
>
> BTW, why did you decide to use get_user_pages?
> Would switch_mm + copy_to_user work as well
> avoiding page walk if all pages are present?
>
Well, basic c_t_u() won't work because its likely not "current" if you
are updating the ring from some other task, but I think you have already
figured that out based on the switch_mm suggestion. The simple truth is
I was not familiar with switch_mm at the time I wrote this (nor am I
now). If this is a superior method that allows you to acquire
c_t_u(some_other_ctx) like behavior, I see no problem in changing. I
will look into this, and thanks for the suggestion!
> Also - if we just had vmexit because a process executed
> io (or hypercall), can't we just do copy_to_user there?
> Avi, I think at some point you said that we can?
>
Right, and yes that will work I believe. We could always do a "if (p ==
current)" check to test for this. To date, I don't typically do
anything mem-ops related directly in vcpu context so this wasn't an
issue...but that doesn't mean someone wont try in the future.
Therefore, I agree we should strive to optimize it if we can.
>
>
Thanks Michael,
-Greg
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 266 bytes --]
next prev parent reply other threads:[~2009-06-04 18:18 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-09 16:30 [RFC PATCH v2 00/19] virtual-bus Gregory Haskins
2009-04-09 16:30 ` [RFC PATCH v2 01/19] shm-signal: shared-memory signals Gregory Haskins
2009-04-09 16:30 ` [RFC PATCH v2 02/19] vbus: add virtual-bus definitions Gregory Haskins
2009-04-09 16:30 ` [RFC PATCH v2 03/19] vbus: add connection-client helper infrastructure Gregory Haskins
2009-06-04 18:06 ` Michael S. Tsirkin
2009-06-04 18:18 ` Gregory Haskins [this message]
2009-06-04 18:24 ` Avi Kivity
2009-06-04 18:30 ` Gregory Haskins
2009-06-04 19:04 ` Avi Kivity
2009-06-04 18:23 ` Avi Kivity
2009-04-09 16:31 ` [RFC PATCH v2 04/19] vbus: add bus-registration notifiers Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 05/19] vbus: add a "vbus-proxy" bus model for vbus_driver objects Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 06/19] ioq: Add basic definitions for a shared-memory, lockless queue Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 07/19] ioq: add vbus helpers Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 08/19] venet: add the ABI definitions for an 802.x packet interface Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 09/19] net: Add vbus_enet driver Gregory Haskins
2009-04-09 16:37 ` Stephen Hemminger
2009-04-09 19:50 ` Greg KH
2009-04-09 16:31 ` [RFC PATCH v2 10/19] venet-tap: Adds a "venet" compatible "tap" device to VBUS Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 11/19] venet: add scatter-gather support Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 12/19] venettap: " Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 13/19] x86: allow the irq->vector translation to be determined outside of ioapic Gregory Haskins
2009-04-09 16:31 ` [RFC PATCH v2 14/19] kvm: add a reset capability Gregory Haskins
2009-04-11 16:56 ` Avi Kivity
2009-04-09 16:32 ` [RFC PATCH v2 15/19] kvm: add dynamic IRQ support Gregory Haskins
2009-04-11 17:01 ` Avi Kivity
2009-04-13 17:44 ` Gregory Haskins
2009-04-09 16:32 ` [RFC PATCH v2 16/19] kvm: Add VBUS support to the host Gregory Haskins
2009-04-09 16:32 ` [RFC PATCH v2 17/19] kvm: Add guest-side support for VBUS Gregory Haskins
2009-04-09 16:32 ` [RFC PATCH v2 18/19] vbus: add a userspace connector Gregory Haskins
2009-04-09 16:32 ` [RFC PATCH v2 19/19] virtio: add a vbus transport Gregory Haskins
2009-08-09 16:40 ` Anthony Liguori
2009-08-10 15:40 ` Gregory Haskins
2009-04-09 16:48 ` [RFC PATCH v2 00/19] virtual-bus Gregory Haskins
2009-04-11 16:45 ` Avi Kivity
2009-06-04 18:49 ` Gregory Haskins
2009-06-05 4:55 ` Rusty Russell
2009-06-05 5:30 ` Paul E. McKenney
2009-06-05 14:55 ` Rusty Russell
2009-06-05 16:25 ` Paul E. McKenney
2009-06-11 13:21 ` Rusty Russell
2009-06-11 15:48 ` Paul E. McKenney
2009-06-05 11:56 ` Gregory Haskins
2009-06-05 12:53 ` Avi Kivity
2009-06-05 12:54 ` Gregory Haskins
2009-06-05 14:35 ` Rusty Russell
2009-06-05 14:44 ` Gregory Haskins
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4A280FE2.2090101@novell.com \
--to=ghaskins@novell.com \
--cc=agraf@suse.de \
--cc=andi@firstfloor.org \
--cc=anthony@codemonkey.ws \
--cc=avi@redhat.com \
--cc=bhutchings@solarflare.com \
--cc=chrisw@sous-sol.org \
--cc=gregkh@suse.de \
--cc=herber@gondor.apana.org.au \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=pmorreale@novell.com \
--cc=pmullaney@novell.com \
--cc=rusty@rustcorp.com.au \
--cc=shemminger@vyatta.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).