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Re: [PATCH v1 10/29] xen/asm-generic: introduce stub header iommu.h
- To: Oleksii <oleksii.kurochko@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 23 Oct 2023 12:47:15 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 23 Oct 2023 10:47:26 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 23.10.2023 12:43, Oleksii wrote:
> On Thu, 2023-10-19 at 11:44 +0200, Jan Beulich wrote:
>> On 14.09.2023 16:56, Oleksii Kurochko wrote:
>>> --- /dev/null
>>> +++ b/xen/include/asm-generic/iommu.h
>>> @@ -0,0 +1,17 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>> +#ifndef __ASM_GENERIC_IOMMU_H__
>>> +#define __ASM_GENERIC_IOMMU_H__
>>> +
>>> +struct arch_iommu {
>>> +};
>>> +
>>> +#endif /* __ASM_IOMMU_H__ */
>> This one's perhaps slightly more "interesting": Yes, we have a
>> HAS_PASSTHROUGH Kconfig option, which both Arm and x86 select. But it
>> is in principle possible to support guests without any kind of IOMMU
>> (permitting solely emulated and PV devices). In which case what's
>> (imo) needed here in addition is
>>
>> #ifdef CONFIG_HAS_PASSTHROUGH
>> # error
>> #endif
> I am not 100% sure but not all platform has support of IOMMU.
>
> And I thought that passthrough it is when a device is fully committed
> to a guest domain with all MMIO things. So it is a question of
> properly mapping MMIO to guest domain. Am I right?
Yes. And do you expect you will get away with such a stub implementation
when you actually start supporting pass-through on RISC-V?
Jan
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