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[34.78.140.88]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438b31c6fbasm21159875e9.33.2025.01.22.03.46.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Jan 2025 03:46:19 -0800 (PST) Date: Wed, 22 Jan 2025 11:46:14 +0000 From: Mostafa Saleh To: Jason Gunthorpe Cc: iommu@lists.linux.dev, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, robdclark@gmail.com, joro@8bytes.org, robin.murphy@arm.com, jean-philippe@linaro.org, nicolinc@nvidia.com, vdonnefort@google.com, qperret@google.com, tabba@google.com, danielmentz@google.com, tzukui@google.com Subject: Re: [RFC PATCH v2 00/58] KVM: Arm SMMUv3 driver for pKVM Message-ID: References: <20241212180423.1578358-1-smostafa@google.com> <20241212194119.GA4679@ziepe.ca> <20250102201614.GA26854@ziepe.ca> <20250116191952.GD674319@ziepe.ca> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250116191952.GD674319@ziepe.ca> On Thu, Jan 16, 2025 at 03:19:52PM -0400, Jason Gunthorpe wrote: > On Wed, Jan 08, 2025 at 12:09:53PM +0000, Mostafa Saleh wrote: > > > I am open to gradually upstream this as you mentioned where as a first > > step pKVM would establish DMA isolation without translation for host, > > that should be enough to have functional pKVM and run protected workloads. > > Personally I hate these giant patch series, you should strip it down > to small meaningful steps and try to stay below 20 per series. > > I think getting pkvm to own the SMMU HW is a great first step that > everything else can build on I plan to do that for v3, I think that also removes the out-of-tree dependencies, so the code applies directly on upstream. Thanks for the feedback! > > > But although that might be usable on some systems, I don’t think that’s > > practical in the long term as it limits the amount of HW that can run pKVM. > > I suspect you will end up doing everything. Old HW needs paravirt, new > HW will want nesting and its performance. Users other than mobile will > come. If we were to use pKVM on server workloads we need nesting for > performance. Yes, I guess that would be the case, as I mentioned in another reply it would be interesting to get the order of magnitude both, which I am looking into, I hope it'd help with which direction we should prioritize upstream. Thanks, Mostafa > > Jason