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Tue, 26 May 2026 05:46:47 -0700 (PDT) Date: Tue, 26 May 2026 12:46:45 +0000 In-Reply-To: <20260526123903.GF2487554@ziepe.ca> Mime-Version: 1.0 References: <20260526123903.GF2487554@ziepe.ca> X-Mailer: git-send-email 2.54.0.746.g67dd491aae-goog Message-ID: <20260526124645.2494330-1-joonwonkang@google.com> Subject: Re: [PATCH v2] iommu: Allow device driver to use its own PASID space for SVA From: Joonwon Kang To: jgg@ziepe.ca Cc: Alexander.Grest@microsoft.com, alexander.shishkin@linux.intel.com, amhetre@nvidia.com, baolu.lu@linux.intel.com, bp@alien8.de, dave.hansen@linux.intel.com, easwar.hariharan@linux.microsoft.com, hpa@zytor.com, iommu@lists.linux.dev, jacob.jun.pan@linux.intel.com, joonwonkang@google.com, joro@8bytes.org, jpb@kernel.org, kas@kernel.org, kees@kernel.org, kevin.tian@intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mingo@redhat.com, nicolinc@nvidia.com, peterz@infradead.org, praan@google.com, robin.murphy@arm.com, ryasuoka@redhat.com, smostafa@google.com, sohil.mehta@intel.com, tglx@kernel.org, will@kernel.org, x86@kernel.org, xin@zytor.com Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260526_054651_230652_82A67B74 X-CRM114-Status: GOOD ( 27.80 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org > On Tue, May 26, 2026 at 12:36:06PM +0000, Joonwon Kang wrote: > > > > From: Joonwon Kang > > > > Sent: Tuesday, May 26, 2026 2:58 PM > > > > > > > > > On Mon, May 25, 2026 at 03:29:24PM +0000, Joonwon Kang wrote: > > > > > > > > > > > Currently, the only known expected user of the new kAPI is our team. > > > > Since > > > > > > I test if the patch resolves our problem before sending it, I believe it > > > > > > should be good enough. Do you mean more than our team by > > > > "accompanied > > > > > > users"? > > > > > > > > > > He means you cannot send patches like this that only serve OOT drivers > > > > > to the mainline kernel. > > > > > > > > Hmm, it gets back to the chicken-and-egg problem. So, do you recommend > > > > deferring the patch submission until we find a new in-tree user of the > > > > new kAPI? I believe we will not make our module in-tree anytime soon. > > > > Or, is it like I still can send the patch and get it reviewed although we > > > > cannot merge it to the mainline? > > > > > > > > > > It's not chicken-and-egg problem. Just always send them together. > > > > > > so let's wait until your module is ready for in-tree review... > > > > Since adding a new kAPI has this limitation, what do you think about the > > idea of adding a new boot parameter to enforce disabling ENQCMD at EL0 and > > using the non-global PASID space in that case? This way, I guess we could > > resolve our issue without having to wait until we have new in-tree users. > > Do you think it should have the same limitation? > > No, you can't hack up the kernel for OOT drivers. Alright, thanks for the confirmation. Thanks, Joonwon Kang