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Message-ID: <aBRA75V9l9WlI2Q3@archie.me>
Date: Fri, 2 May 2025 10:50:07 +0700
From: Bagas Sanjaya <bagasdotme@...il.com>
To: Nicolin Chen <nicolinc@...dia.com>, jgg@...dia.com,
kevin.tian@...el.com, corbet@....net, will@...nel.org
Cc: robin.murphy@....com, joro@...tes.org, thierry.reding@...il.com,
vdumpa@...dia.com, jonathanh@...dia.com, shuah@...nel.org,
jsnitsel@...hat.com, nathan@...nel.org, peterz@...radead.org,
yi.l.liu@...el.com, mshavit@...gle.com, praan@...gle.com,
zhangzekun11@...wei.com, iommu@...ts.linux.dev,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
linux-kselftest@...r.kernel.org, patches@...ts.linux.dev,
mochs@...dia.com, alok.a.tiwari@...cle.com, vasant.hegde@....com
Subject: Re: [PATCH v3 16/23] Documentation: userspace-api: iommufd: Update
vQUEUE
On Thu, May 01, 2025 at 04:01:22PM -0700, Nicolin Chen wrote:
> +- IOMMUFD_OBJ_VQUEUE, representing a hardware accelerated virtual queue, as a
> + subset of IOMMU's virtualization features, for the IOMMU HW to directly read
> + or write the virtual queue memory owned by a guest OS. This HW-acceleration
> + allows VM to work with the IOMMU HW directly without a VM Exit, i.e. reducing
> + overhead from the hypercalls. Along with this vQUEUE object, iommufd provides
> + user space an mmap interface for VMM to mmap a physical MMIO region from the
> + host physical address space to the guest physical address space, allowing the
> + guest OS to control the allocated vQUEUE HW. Thus, when allocating a vQUEUE,
> + the VMM must request a pair of VMA info (vm_pgoff/size) for an mmap syscall.
> + The length argument of an mmap syscall can be smaller than the given size for
> + a partial mmap, but the addr argument of the mmap syscall should never offset
> + from the returned vm_pgoff, which implies that an mmap will always start from
Did you mean never be offset from returned vm_pgoff?
> + the beginning of the physical MMIO region.
> +
Confused...
--
An old man doll... just what I always wanted! - Clara
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