From: Anthony Liguori <anthony@codemonkey.ws> To: Avi Kivity <avi@qumranet.com> Cc: Arjan van de Ven <arjan@infradead.org>, kvm-devel@lists.sourceforge.net, akpm@osdl.org, Pavel Machek <pavel@ucw.cz>, linux-kernel@vger.kernel.org Subject: Re: [kvm-devel] [PATCH 10/13] KVM: Wire up hypercall handlers to a central arch-independent location Date: Fri, 23 Feb 2007 08:55:48 -0600 [thread overview] Message-ID: <45DF0074.9050506@codemonkey.ws> (raw) In-Reply-To: <45DDA6CB.4020603@qumranet.com> Avi Kivity wrote: > Arjan van de Ven wrote: > >>> Can't it be done by a helper function using a timer and a signal (or >>> whatever mechanism we use to wake up vcpus)? >>> >>> >> one could do that but it's not optimal; if the process DOES get waken up >> earlier, it should take the interrupt then immediately, so that it >> doesn't have to wake up again when the timer fires. >> >> (in fact it would be nice if the guest could somehow poll at the irq >> mask at waking from idle, so that it wouldn't need a vmexit/entry for >> every such interrupt, but just do the right thing for all pending work) >> >> In addition, yes it'll be a helper function, but since all drivers will >> want the functionality its probably best off in the generic code >> >> >> > > That's what Xen does (I'm not sure about the timer, but they do avoid > unnecessary interrupts). As you can have memory shared between the > guest and host, it's quite simple: > > 0. host puts data in ring > 1. host sets interrupt timer > 2. guest wakes up for unrelated reasons > 3. guest sees data in ring, consumes it, and bumps the consumer pointer > 4. timer fires, host sees consumer == producer, no need to issue interrupt > It's not quite a timer. It's an asynchronous notification mechanism. Guest sets a bit in the appropriate domain's shared_info and when the domain gets scheduled again, it checks it's bits. An easy way to simulate this in KVM would be to have the guest set a bit in the paravirt page and then on the next trip down to userspace, we check the bits and dispatch appropriately. We know we'll get down to userspace at least for the next EINTR. > They have that code abstracted out and reusable by multiple drivers. > Why don't we see how many drivers we get first. I have my doubts that a paravirt disk driver will significantly out perform scsi emulation. Regards, Anthony Liguori
WARNING: multiple messages have this Message-ID (diff)
From: Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org> To: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org> Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, akpm-3NddpPZAyC0@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Pavel Machek <pavel-+ZI9xUNit7I@public.gmane.org> Subject: Re: [PATCH 10/13] KVM: Wire up hypercall handlers to a central arch-independent location Date: Fri, 23 Feb 2007 08:55:48 -0600 [thread overview] Message-ID: <45DF0074.9050506@codemonkey.ws> (raw) In-Reply-To: <45DDA6CB.4020603-atKUWr5tajBWk0Htik3J/w@public.gmane.org> Avi Kivity wrote: > Arjan van de Ven wrote: > >>> Can't it be done by a helper function using a timer and a signal (or >>> whatever mechanism we use to wake up vcpus)? >>> >>> >> one could do that but it's not optimal; if the process DOES get waken up >> earlier, it should take the interrupt then immediately, so that it >> doesn't have to wake up again when the timer fires. >> >> (in fact it would be nice if the guest could somehow poll at the irq >> mask at waking from idle, so that it wouldn't need a vmexit/entry for >> every such interrupt, but just do the right thing for all pending work) >> >> In addition, yes it'll be a helper function, but since all drivers will >> want the functionality its probably best off in the generic code >> >> >> > > That's what Xen does (I'm not sure about the timer, but they do avoid > unnecessary interrupts). As you can have memory shared between the > guest and host, it's quite simple: > > 0. host puts data in ring > 1. host sets interrupt timer > 2. guest wakes up for unrelated reasons > 3. guest sees data in ring, consumes it, and bumps the consumer pointer > 4. timer fires, host sees consumer == producer, no need to issue interrupt > It's not quite a timer. It's an asynchronous notification mechanism. Guest sets a bit in the appropriate domain's shared_info and when the domain gets scheduled again, it checks it's bits. An easy way to simulate this in KVM would be to have the guest set a bit in the paravirt page and then on the next trip down to userspace, we check the bits and dispatch appropriately. We know we'll get down to userspace at least for the next EINTR. > They have that code abstracted out and reusable by multiple drivers. > Why don't we see how many drivers we get first. I have my doubts that a paravirt disk driver will significantly out perform scsi emulation. Regards, Anthony Liguori ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
next prev parent reply other threads:[~2007-02-23 14:55 UTC|newest] Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-02-19 10:20 [PATCH 0/13] kvm updates for 2.6.21 Avi Kivity 2007-02-19 10:20 ` Avi Kivity 2007-02-19 10:21 ` [PATCH 1/13] KVM: mmu: add missing dirty page tracking cases Avi Kivity 2007-02-19 10:21 ` Avi Kivity 2007-02-19 10:22 ` [PATCH 2/13] KVM: Move virtualization deactivation from CPU_DEAD state to CPU_DOWN_PREPARE Avi Kivity 2007-02-19 10:22 ` Avi Kivity 2007-02-19 10:23 ` [PATCH 3/13] KVM: Cosmetics Avi Kivity 2007-02-19 10:23 ` Avi Kivity 2007-02-19 10:24 ` [PATCH 4/13] KVM: vmx: hack set_cr0_no_modeswitch() to actually do modeswitch Avi Kivity 2007-02-19 10:24 ` Avi Kivity 2007-02-19 10:25 ` [PATCH 5/13] KVM: Use ARRAY_SIZE macro instead of manual calculation Avi Kivity 2007-02-19 10:25 ` Avi Kivity 2007-02-19 10:26 ` [PATCH 6/13] KVM: Use page_private()/set_page_private() apis Avi Kivity 2007-02-19 10:26 ` Avi Kivity 2007-02-19 10:27 ` [PATCH 7/13] KVM: add MSR based hypercall API Avi Kivity 2007-02-19 10:27 ` Avi Kivity 2007-02-19 10:28 ` [PATCH 8/13] KVM: Add host hypercall support for vmx Avi Kivity 2007-02-19 10:28 ` Avi Kivity 2007-02-19 10:29 ` [PATCH 9/13] KVM: Add hypercall host support for svm Avi Kivity 2007-02-19 10:29 ` Avi Kivity 2007-02-19 10:30 ` [PATCH 10/13] KVM: Wire up hypercall handlers to a central arch-independent location Avi Kivity 2007-02-19 10:30 ` Avi Kivity 2007-02-21 10:37 ` Pavel Machek 2007-02-21 10:37 ` Pavel Machek 2007-02-22 10:14 ` Avi Kivity 2007-02-22 10:14 ` Avi Kivity 2007-02-22 10:17 ` [kvm-devel] " Dor Laor 2007-02-22 10:17 ` Dor Laor 2007-02-22 10:22 ` [kvm-devel] " Joerg Roedel 2007-02-22 10:22 ` Joerg Roedel 2007-02-22 10:37 ` [kvm-devel] " Avi Kivity 2007-02-22 10:37 ` Avi Kivity 2007-02-22 10:34 ` [kvm-devel] " Arjan van de Ven 2007-02-22 10:34 ` Arjan van de Ven 2007-02-22 10:40 ` [kvm-devel] " Avi Kivity 2007-02-22 10:40 ` Avi Kivity 2007-02-22 11:01 ` [kvm-devel] " Arjan van de Ven 2007-02-22 11:01 ` Arjan van de Ven 2007-02-22 13:04 ` [kvm-devel] " Avi Kivity 2007-02-22 13:04 ` Avi Kivity 2007-02-22 13:12 ` [kvm-devel] " Arjan van de Ven 2007-02-22 13:29 ` Avi Kivity 2007-02-22 13:29 ` Avi Kivity 2007-02-22 14:09 ` [kvm-devel] " Arjan van de Ven 2007-02-22 14:09 ` Arjan van de Ven 2007-02-22 14:20 ` [kvm-devel] " Avi Kivity 2007-02-22 14:20 ` Avi Kivity 2007-02-23 14:55 ` Anthony Liguori [this message] 2007-02-23 14:55 ` Anthony Liguori 2007-02-22 13:31 ` [kvm-devel] [PATCH 10/13] KVM: Wire up hypercall handlers toa " Dor Laor 2007-02-22 13:31 ` Dor Laor [not found] ` <1172142081.3531.243.camel-NIQFrBLA1CpScpXdPBN83iCwEArCW2h5@public.gmane.org> 2007-02-23 21:14 ` Booting from PV disk driver (Was: Re: [PATCH 10/13] KVM: Wire up hypercall handler ..) Anthony Liguori [not found] ` <45DF5943.3090304-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org> 2007-02-23 22:33 ` Arjan van de Ven [not found] ` <1172269981.3241.57.camel-NIQFrBLA1CpScpXdPBN83iCwEArCW2h5@public.gmane.org> 2007-02-24 22:35 ` Booting from PV disk driver (Was: Re: [PATCH 10/13]KVM: " Dor Laor [not found] ` <64F9B87B6B770947A9F8391472E032160A91C385-yEcIvxbTEBqsx+V+t5oei8rau4O3wl8o3fe8/T/H7NteoWH0uzbU5w@public.gmane.org> 2007-02-25 5:20 ` Avi Kivity [not found] ` <45E11C8A.9070006-atKUWr5tajBWk0Htik3J/w@public.gmane.org> 2007-02-25 5:48 ` Avi Kivity 2007-02-25 5:17 ` Booting from PV disk driver (Was: Re: [PATCH 10/13] KVM: " Avi Kivity [not found] ` <45E11C00.2000602-atKUWr5tajBWk0Htik3J/w@public.gmane.org> 2007-02-25 6:31 ` Arjan van de Ven [not found] ` <1172385067.3265.1.camel-NIQFrBLA1CpScpXdPBN83iCwEArCW2h5@public.gmane.org> 2007-02-25 6:34 ` Avi Kivity [not found] ` <45E12E08.8040402-atKUWr5tajBWk0Htik3J/w@public.gmane.org> 2007-02-25 6:42 ` Arjan van de Ven [not found] ` <1172385720.3265.12.camel-NIQFrBLA1CpScpXdPBN83iCwEArCW2h5@public.gmane.org> 2007-02-25 6:52 ` Avi Kivity [not found] ` <45E13213.5070502-atKUWr5tajBWk0Htik3J/w@public.gmane.org> 2007-02-25 6:56 ` Arjan van de Ven 2007-02-19 10:31 ` [PATCH 11/13] KVM: svm: init cr0 with the wp bit set Avi Kivity 2007-02-19 10:31 ` Avi Kivity 2007-02-19 10:32 ` [PATCH 12/13] KVM: SVM: intercept SMI to handle it at host level Avi Kivity 2007-02-19 10:33 ` [PATCH 13/13] KVM: More 0 -> NULL conversions Avi Kivity 2007-02-19 10:33 ` Avi Kivity
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=45DF0074.9050506@codemonkey.ws \ --to=anthony@codemonkey.ws \ --cc=akpm@osdl.org \ --cc=arjan@infradead.org \ --cc=avi@qumranet.com \ --cc=kvm-devel@lists.sourceforge.net \ --cc=linux-kernel@vger.kernel.org \ --cc=pavel@ucw.cz \ /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: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.