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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Bjorn Helgaas , Jaroslav Kysela , Takashi Iwai Cc: Han Gao , Vivian Wang , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, netdev@vger.kernel.org, linux-pci@vger.kernel.org, linux-sound@vger.kernel.org, linux-riscv@lists.infradead.org, sophgo@lists.linux.dev, Takashi Iwai Subject: Re: [PATCH v3 1/4] PCI/MSI: Conservatively generalize no_64bit_msi into msi_addr_mask In-Reply-To: <20260123-pci-msi-addr-mask-v3-1-9f9baa048524@iscas.ac.cn> References: <20260123-pci-msi-addr-mask-v3-0-9f9baa048524@iscas.ac.cn> <20260123-pci-msi-addr-mask-v3-1-9f9baa048524@iscas.ac.cn> Date: Tue, 27 Jan 2026 10:25:46 +0100 Message-ID: <87o6mfbe5h.ffs@tglx> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain On Fri, Jan 23 2026 at 14:07, Vivian Wang wrote: > Some PCI devices have PCI_MSI_FLAGS_64BIT in the MSI capability, but > implement less than 64 address bits. This breaks on platforms where such > a device is assigned an MSI address higher than what's reachable. > > Currently, we deal with this with a single no_64bit_msi flag, and we don't deal with anything. The code has a single bit limitation. Please use passive voice as documented. > (notably on powerpc) forces 32-bit MSI address for these devices. this is not a valid sentence. > However, on some platforms the MSI doorbell address is above 32-bit but > within device ability. > > As a first step to enabling MSI on those combinations of devices and > platforms, conservatively generalize the single-bit flag no_64bit_msi > into msi_addr_mask. (The name msi_addr_mask is chosen to avoid confusion > with msi_mask.) > > The translation is essentially: > > - no_64bit_msi = 1 -> msi_addr_mask = DMA_BIT_MASK(32) > - no_64bit_msi = 0 -> msi_addr_mask = DMA_BIT_MASK(64) > - if (no_64bit_msi) -> if (msi_addr_mask < DMA_BIT_MASK(64)) > > Since no values other than DMA_BIT_MASK(32) and DMA_BIT_MASK(64) is s/is/are/ > used, no functional change is intended. Future patches that make use of > intermediate values of msi_addr_mask will follow, allowing devices that > cannot use full 64-bit addresses for MSI to work on platforms with MSI > doorbell above 32-bit address space. > > Acked-by: Takashi Iwai > Signed-off-by: Vivian Wang Other than those nits: Reviewed-by: Thomas Gleixner