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Tue, 10 Nov 2026 05:47:15 -0800 (PST) Received: from [192.168.50.100] ([114.252.97.9]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8baaae3e110sm867486b3a.36.2026.11.10.05.47.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Nov 2026 05:47:15 -0800 (PST) Message-ID: <42ce73bc-0fb5-46d9-bc45-34a5bef25cb2@gmail.com> Date: Tue, 10 Nov 2026 21:47:05 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v2 9/9] iommu/riscv: Add riscv_iommu_attach_dev_nested To: Jason Gunthorpe , Gong Shuai Cc: tanchi25@mails.ucas.ac.cn, alex@ghiti.fr, andrew.jones@oss.qualcomm.com, anup@brainfault.org, aou@eecs.berkeley.edu, atish.patra@linux.dev, fangyu.yu@linux.alibaba.com, iommu@lists.linux.dev, joro@8bytes.org, kevin.tian@intel.com, kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, palmer@dabbelt.com, pbonzini@redhat.com, pjw@kernel.org, robin.murphy@arm.com, seanjc@google.com, tomasz.jeznach@linux.dev, will@kernel.org, wu.fei9@sanechips.com.cn, zhao.qingye@sanechips.com.cn References: <20261105144944.10193-1-tanchi25@mails.ucas.ac.cn> <20261110115137.184160-1-gong.shuai@sanechips.com.cn> <20261110131658.GW663069@ziepe.ca> From: Gong Shuai In-Reply-To: <20261110131658.GW663069@ziepe.ca> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Jason, On 11/10/2026 9:16 PM, Jason Gunthorpe wrote: > On Tue, Nov 10, 2026 at 07:51:37PM +0800, Gong Shuai wrote: > >> 2. Use the guest PSCID directly, but allocate a separate host GSCID for >> each vIOMMU. > > This is the right model. The viommu should allocate the GSCID directly > and keep it for the lifetime of the VM. Thanks for the confirmation. The new version will use this scheme. > >> 3. Share the GSCID and maintain a per-vIOMMU mapping from each guest >> PSCID to a host-allocated PSCID. > > AMD is doing this because they don't have something like a GSCID. Understood. This approach makes sense. Thanks, Shuai > > Jason