From: Paolo Bonzini <pbonzini@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
qemu-devel@nongnu.org, "Peter Maydell" <peter.maydell@linaro.org>,
"Alexey Kardashevskiy" <aik@ozlabs.ru>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Alex Williamson" <alex.williamson@redhat.com>
Subject: Re: [PATCH] memory: Do not allow subregion out of the parent region range
Date: Tue, 17 Dec 2019 11:51:39 +0100 [thread overview]
Message-ID: <4a07cc6f-8762-145e-2b54-c61b0e287f19@redhat.com> (raw)
In-Reply-To: <92bb8e12-3ece-9811-438b-8fa64d2bde66@redhat.com>
On 16/12/19 18:46, Philippe Mathieu-Daudé wrote:
>>>
>>
>> I think in some cases this could be intentional, for example if you have
>> different models with different BAR sizes and you organize this with the
>> same tree of MemoryRegion and different sizes for the parent.
>
> But if a child is outside of the parent range, it can't be reached,
> right? I'm confused, maybe AddressSpace can do that, but MemoryRegion
> shouldn't?
Yes, the idea is that you could have for one version of the device
parent 0x000-0x7ff
stuff 0x000-0x3ff
morestuff 0x400-0x7ff
and for another
parent 0x000-0x3ff
stuff 0x000-0x3ff
morestuff 0x400-0x7ff
where parent is the BAR, and you can share the code to generate the tree
underneath parent.
> In the PCI case, you will simply alias a subregion with
> memory_region_init_alias(..., size), and size has to be <= parent size.
> But you won't add the PCI region, you'll add the alias, so the assert
> won't fire.
Yes, this is a workaround though. You shouldn't need the alias.
I can see a case for your patch but I can also see one for the current
behavior...
Paolo
next prev parent reply other threads:[~2019-12-17 10:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-14 16:02 [PATCH] memory: Do not allow subregion out of the parent region range Philippe Mathieu-Daudé
2019-12-16 13:08 ` Paolo Bonzini
2019-12-16 17:46 ` Philippe Mathieu-Daudé
2019-12-17 10:51 ` Paolo Bonzini [this message]
2019-12-17 11:58 ` Christophe de Dinechin
2019-12-17 16:57 ` Richard Henderson
2019-12-17 18:17 ` Peter Maydell
2019-12-17 18:31 ` Paolo Bonzini
2019-12-17 18:52 ` Alex Williamson
2019-12-17 19:17 ` Philippe Mathieu-Daudé
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