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Mon, 3 Aug 2026 17:39:17 -0500 (CDT) Received: from vali.starlink.edu (localhost [127.0.0.1]) by mail.rptsys.com (Postfix) with ESMTP id 8C90077926B6 for ; Mon, 3 Aug 2026 17:39:17 -0500 (CDT) Date: Mon, 3 Aug 2026 17:39:14 -0500 (CDT) From: Timothy Pearson To: linuxppc-dev Message-ID: <334689093.41938.1785796754275.JavaMail.zimbra@raptorengineeringinc.com> Subject: [BUG] VFIO on POWER9 / QEMU fails to allocate 32-bit DMA 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; charset=utf-8 Content-Transfer-Encoding: 7bit X-Mailer: Zimbra 8.5.0_GA_3042 (ZimbraWebClient - GC151 (Linux)/8.5.0_GA_3042) Thread-Index: 9LxrnSw+cEMdPsRCafYWajf8BqSmeQ== Thread-Topic: VFIO on POWER9 / QEMU fails to allocate 32-bit DMA On Linux 6.18, and potentially earlier Linux versions, attempting to pass through any PCI device via VFIO that requires 32-bit DMA results in the following error in the guest VM: [ 11.705413] cx23885 0000:00:02.0: Warning: IOMMU offset too big for device mask [ 11.709245] cx23885 0000:00:02.0: mask: 0xffffffff, table offset: 0x800000000000000 The same devices work correctly on the host kernel. It appears that somehow 32-bit DMA is not available within a pSeries guest on a PowerNV host.