From: BALATON Zoltan <balaton@eik.bme.hu>
To: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Huacai Chen" <chenhuacai@kernel.org>,
"Mark Cave-Ayland" <mark.cave-ayland@ilande.co.uk>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
"BALATON Zoltan via" <qemu-devel@nongnu.org>,
"Hervé Poussineau" <hpoussin@reactos.org>
Subject: Re: [PATCH v2 08/13] vt82c686: Move creation of ISA devices to the ISA bridge
Date: Mon, 11 Jan 2021 11:28:40 +0100 (CET) [thread overview]
Message-ID: <2e29d39-8622-3232-d6cd-80d77beb98@eik.bme.hu> (raw)
In-Reply-To: <f5466f0b-cc4f-4a71-8c06-7971198a7602@www.fastmail.com>
[-- Attachment #1: Type: text/plain, Size: 2027 bytes --]
On Mon, 11 Jan 2021, Jiaxun Yang wrote:
> On Mon, Jan 11, 2021, at 3:25 AM, BALATON Zoltan wrote:
>> On Sun, 10 Jan 2021, Philippe Mathieu-Daudé wrote:
>>> +PCI experts
>>>
>>> On 1/10/21 1:43 AM, BALATON Zoltan wrote:
>>>> On Sun, 10 Jan 2021, Philippe Mathieu-Daudé wrote:
>
> [...]
>
>>> I'm not a PCI expert but my understanding is PCI device functions are
>>> restricted to the PCI bus address space. The host bridge may map this
>>> space within the host.
>>>
>>> QEMU might be using get_system_memory() because for some host bridge
>>> the mapping is not implemented so it was easier this way?
>>
>> Maybe, also one less indirection which if not really needed is a good
>> thing for performance so unless it's found to be needed to use another
>> address space here I'm happy with this as it matches what other similar
>> devices do and it seems to work. Maybe a separate address space is only
>> really needed if we have an iommu?
>
> Hi Zoltan,
>
> It is possible for bonito to remap PCI address space so maybe it's essential for bonito.
I'm still not sure it's needed or how that would work. Maybe while it's
possible to remap these, all guests just map these one-to-one (otherwise
they may need to do some address translation which is much better avoided)
so in practice we don't need to emulate this. If we use a different memory
region maybe we also need some additional iommu code somewhere to connect
the two but I'm not sure, I haven't tried since most other isa bridges do
the same way using system_memory and this seems to work. I'm also a bit
concerned about additional overhead which we could avoid if possible. Just
to model something that's not really used I don't think it's worth the
additional complexity and possible performance loss unless it's found to
be needed to get some guests work.
> Appreciate for your work. I'm going to help with reviewing as well.
Thanks, I hope to get these in now before the freeze so testing and
reviewing is really appreciated.
Regards,
BALATON Zoltan
next prev parent reply other threads:[~2021-01-11 10:29 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-09 20:16 [PATCH v2 00/13] vt82c686b clean ups and vt8231 emulation BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 07/13] vt82c686: Simplify vt82c686b_realize() BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 04/13] vt82c686: Fix up power management io base and config BALATON Zoltan
2021-02-20 18:58 ` Philippe Mathieu-Daudé
2021-02-20 22:33 ` BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 11/13] vt82c686: QOM-ify superio related functionality BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 13/13] vt82c686: Add emulation of VT8231 south bridge BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 01/13] vt82c686: Move superio memory region to SuperIOConfig struct BALATON Zoltan
2021-01-10 0:06 ` Philippe Mathieu-Daudé
2021-01-13 2:26 ` Jiaxun Yang
2021-01-09 20:16 ` [PATCH v2 09/13] vt82c686: Fix superio_cfg_{read,write}() functions BALATON Zoltan
2021-02-20 19:24 ` Philippe Mathieu-Daudé
2021-02-20 22:00 ` BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 12/13] vt82c686: Add VT8231_SUPERIO based on VIA_SUPERIO BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 10/13] vt82c686: Implement control of serial port io ranges via config regs BALATON Zoltan
2021-02-20 19:30 ` Philippe Mathieu-Daudé
2021-02-20 22:53 ` BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 02/13] vt82c686: Reorganise code BALATON Zoltan
2021-01-09 20:16 ` [PATCH v2 05/13] vt82c686: Set user_creatable=false for VT82C686B_PM BALATON Zoltan
2021-01-09 23:41 ` Philippe Mathieu-Daudé
2021-01-13 2:27 ` Jiaxun Yang
2021-01-09 20:16 ` [PATCH v2 06/13] vt82c686: Make vt82c686b-pm an abstract base class and add vt8231-pm based on it BALATON Zoltan
2021-01-09 23:42 ` Philippe Mathieu-Daudé
2021-01-09 20:16 ` [PATCH v2 03/13] vt82c686: Fix SMBus IO base and configuration registers BALATON Zoltan
2021-01-12 12:54 ` Jiaxun Yang
2021-01-12 22:25 ` BALATON Zoltan
2021-01-13 2:24 ` Jiaxun Yang
2021-01-09 20:16 ` [PATCH v2 08/13] vt82c686: Move creation of ISA devices to the ISA bridge BALATON Zoltan
2021-01-10 0:21 ` Philippe Mathieu-Daudé
2021-01-10 0:43 ` BALATON Zoltan
2021-01-10 11:34 ` Philippe Mathieu-Daudé
2021-01-10 19:25 ` BALATON Zoltan
2021-01-11 1:38 ` Jiaxun Yang
2021-01-11 10:28 ` BALATON Zoltan [this message]
2021-01-25 17:57 ` Philippe Mathieu-Daudé
2021-02-01 20:04 ` BALATON Zoltan
2021-02-04 12:35 ` Jiaxun Yang
2021-02-04 13:10 ` BALATON Zoltan
2021-02-09 16:55 ` BALATON Zoltan
2021-02-17 20:36 ` BALATON Zoltan
2021-02-21 9:48 ` [PATCH v2 00/13] vt82c686b clean ups and vt8231 emulation Philippe Mathieu-Daudé
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