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[71.194.28.115]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50b36cb2e29sm35646841cf.1.2026.03.20.16.38.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Mar 2026 16:38:50 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-renesas-soc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 20 Mar 2026 18:38:47 -0500 Message-Id: Cc: "Peter Maydell" , "Auger Eric" , "Xiao Feng Ren" , "Arnd Bergmann" , "Alexander Graf" , "Magnus Damm" , "Laurent Pinchart" , "Wolfram Sang" , "Landon Clipp" , , , Subject: Re: [Qemu-arm] [PATCH/RFC 4/5] vfio: No-IOMMU mode support From: "Landon Clipp" To: "Alex Williamson" , "Geert Uytterhoeven" X-Mailer: aerc 0.21.0 References: <1518189456-2873-1-git-send-email-geert+renesas@glider.be> <1518189456-2873-5-git-send-email-geert+renesas@glider.be> <20180209085024.004b6f9e@w520.home> In-Reply-To: <20180209085024.004b6f9e@w520.home> On Fri Feb 9, 2018 at 9:50 AM CST, Alex Williamson wrote: > On Fri, 9 Feb 2018 16:17:35 +0100 > Geert Uytterhoeven wrote: > >> From: Xiao Feng Ren >>=20 >> Add qemu support for the newly introduced VFIO No-IOMMU driver. >>=20 >> We need to add special handling for: >> - Group character device is /dev/vfio/noiommu-$GROUP. >> - No-IOMMU does not rely on a memory listener. >> - No IOMMU will be set for its group, so no need to call >> vfio_kvm_device_add_group. >>=20 >> Signed-off-by: Xiao Feng Ren >> [geert: Rebase] >> Signed-off-by: Geert Uytterhoeven >> --- >> hw/vfio/common.c | 61 ++++++++++++++++++++++++++++++++++--= ------- >> include/hw/vfio/vfio-common.h | 2 ++ >> 2 files changed, 50 insertions(+), 13 deletions(-) > > NAK. I'm opposed to no-iommu support in QEMU in general, but accepting > vfio devices with no-iommu (which provide no DMA translation!!!) > transparently as if they might actually work like a regular vfio device > is absolutely unacceptable. Without DMA translation and isolation, you > might want to think about another interface, I'm not keen on the idea > of corrupting vfio support in order to blink some LEDs. Thanks, > > Alex > 8 years later, I was wondering if we could revisit this. I found myself in = a need to use enable_unsafe_noiommu_mode due to some systems I'm using not ha= ving a usable IOMMU. QEMU is being used as part of a single-tenant workload sandboxing environment, and given the specific circumstances, both the user= s and the administrators understand that enabling the noiommu mode is unsafe and cannot be used where security matters. Regardless, it's still something we = want. As the administrator of my system, it's under my control whether VFIO is pu= t into this mode, and if it is, I would expect the remaning software componen= ts to respect that decision. As is, the system is unusable because of a lack o= f support in QEMU. I'm happy to elucidate more of my use-case if it is helpful, but I first wa= nted to gauge your willingness to reconsider this under a different context. Regards, Landon (CoreWeave)