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Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt
From: |
Gerd Hoffmann |
Subject: |
Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking |
Date: |
Tue, 18 Dec 2012 12:03:25 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:10.0.11) Gecko/20121116 Thunderbird/10.0.11 |
Hi,
> Can qemu not handle an mmio range where writes are trapped, but reads are
> not? That would force the use of the shadow variable, but should otherwise
> provide a nice speedup.
No. vmexit is needed anyway btw, but the round-trip to qemu userspace
could be short-cutted in theory. It's non-trivial though. Alex had a
talk about it at kvm forum (covering ide).
First a simple read directly + write via qemu isn't that useful. You
need a policy per register.
For most reads it would work, but there are exceptions. Registers
holding timers for example. frindex is actually an example of that.
With async_stepdown active frindex updates are quite jumpy. We might
want to update the register on guest reads (and maybe also reset async
stepdown in that case).
Likewise the other way around: Not all register writes have some effect
which qemu must emulate, some are just storage (like ehci frame list
address).
Locking is an unsolved issue (in-kernel register reads/writes don't grab
the qemu lock and thus would race with iothread accessing the register
variables).
cheers,
Gerd
- [Qemu-devel] [PATCH 04/26] ehci: Move get / put_dwords upwards, (continued)
- [Qemu-devel] [PATCH 04/26] ehci: Move get / put_dwords upwards, Hans de Goede, 2012/12/14
- [Qemu-devel] [PATCH 08/26] ehci: Verify a queue's ep direction does not change, Hans de Goede, 2012/12/14
- [Qemu-devel] [PATCH 07/26] ehci: Add an ehci_get_pid helper function, Hans de Goede, 2012/12/14
- [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking, Hans de Goede, 2012/12/14
- Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking, Gerd Hoffmann, 2012/12/17
- Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking, Hans de Goede, 2012/12/17
- Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking, Gerd Hoffmann, 2012/12/17
- Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking, Hans de Goede, 2012/12/17
- Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking, Gerd Hoffmann, 2012/12/17
- Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking, Hans de Goede, 2012/12/18
- Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking,
Gerd Hoffmann <=
- Re: [Qemu-devel] [PATCH 09/26] ehci: Use uframe precision for interrupt threshold checking, Hans de Goede, 2012/12/18
[Qemu-devel] [PATCH 12/26] uhci: Fix 1 ms delay in interrupt reporting to the guest, Hans de Goede, 2012/12/14
[Qemu-devel] [PATCH 10/26] ehci: Further speedup rescanning if async schedule after raising an interrupt, Hans de Goede, 2012/12/14
[Qemu-devel] [PATCH 11/26] ehci: Don't call commit_irq after raising PCD, Hans de Goede, 2012/12/14
[Qemu-devel] [PATCH 13/26] uhci: Fix pending interrupts getting lost on migration, Hans de Goede, 2012/12/14
[Qemu-devel] [PATCH 14/26] uhci: Add a QH_VALID define, Hans de Goede, 2012/12/14
[Qemu-devel] [PATCH 17/26] hid: Change idle handling to use a timer, Hans de Goede, 2012/12/14
[Qemu-devel] [PATCH 15/26] uhci: Limit amount of frames processed in one go, Hans de Goede, 2012/12/14
[Qemu-devel] [PATCH 20/26] usbredir: Add an usbredir_stop_ep helper function, Hans de Goede, 2012/12/14
[Qemu-devel] [PATCH 19/26] usb: Add an usb_device_ep_stopped USBDevice method, Hans de Goede, 2012/12/14