From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CEC6D4A33F2 for ; Tue, 12 May 2026 10:07:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778580465; cv=none; b=WqAhmT0ay0DeVoOe8TiVnqFOeEnTqjyynWSZcAgApKHhYHXfDSjThFMl5iLGDzam4zM2IfJKLZ3HVi+JkP2T/69bAUYXiVo3h8o3jmS6a61pVS97tei0wCYZIpPvp5X1XAMhQ6o7oimqg6hzLABOAy0LxvdrnX1umlvaduEAi/E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778580465; c=relaxed/simple; bh=UZuNloMwiW+tHrGQ6MZ2lLA+dVPzlHThABVURqhAJtI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=eQrVbTqkKMtHqClys2f7hIFyFwMBivIuQPwdLgTJenxgrjO+byrBB2Vzw9/91TnFz/sFkJtPMQMFnRtBLrYGAr8uYBPtoJcsidFx90yPk79fQUM8/qutM08c7/eiVe8EvAEyLesApfW8GlBF2suz/LBhEey7kfauRmtaw4M8VRA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--joonwonkang.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Rcfggobm; arc=none smtp.client-ip=209.85.214.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--joonwonkang.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Rcfggobm" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2b4678c6171so56077565ad.1 for ; Tue, 12 May 2026 03:07:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1778580464; x=1779185264; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=4BRCH8Q+sSIoCslEFIamY+nsMlk/tKqIeqWpZmZWSTw=; b=RcfggobmCayLBWKeYlSb+0qBGCM3ynb8EQ1wIbZGGoQHZ4Yvh9bbHS6fuMIZUYU+vO 1lzDTbaTjGAfRwD/hIb+fuzDT+KnQ2T1Er5DJkl3IJ3053D/z7WCPFp7EZ7dgrhsJF5I I56Hf8ANnzKXbTXtYjKpxKVJun/PiFzVXEvjdfWEQPlKDQEtpJenPWNn9q2sTr178Ufg SJqxZVdb9p9O9fZX8uo8DtzqYJElXIQn3jN+XeMzPk+CfbIJV7icdrQUM363DHwTUdKL rbZmxDl5Q7A9XTRJMOUCoIsWOnGB6eHb3f1uU/sM/UHuILLsK9xmIubY+1sz92ZuXRpB eO1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778580464; x=1779185264; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=4BRCH8Q+sSIoCslEFIamY+nsMlk/tKqIeqWpZmZWSTw=; b=mx6nDKZsupb84DUIYo/Oooa/uP/6xfTPezditQf/nDqNRTtpKsQvKj/+21ZtjGeuBh 9GTwHFqWwSTHhFo6irhwbWRNAiXX6D1ycSjcWZkpXzMsELpp/Hb//x13EvWtwq33v5n2 jcbZ1wGpCwdy1ELxlobeN1AiAZIdmqKygcm4fVpz7nONZ7xQqkr6IEb/4GKYbaNuxow9 r0hoXyoHj55yr5lACyVI1U/PmBQ2vYgxiIkz+Rvv6f4hM+S8Vrkn00c3f3m4cBh43LL5 xQH2UAswv3en2LvvduJMlLWczp7rUy8+rN7qRvLGQeS6LGmTBGgNZ3PEpGAJ6Jrezslm aoHg== X-Forwarded-Encrypted: i=1; AFNElJ++o0kPmzotfnweggIRzgy+Tyb0nZYlioyMV1LCvPzUJ7+0fZsTuGNoXYM+fFq5utdX5rGZT99Op3NadVo=@vger.kernel.org X-Gm-Message-State: AOJu0Yzbyyc8IQtxe9be9B5+lgqPBOsap6XjUUjX3qFyj+XTOK1IDWls ECrLx4ROPFoQXqYNPciUFHSLoPqHFHBiHP84uwC6+SKXTWI9dRBdB1dMWSJV0jGmTPk6Iazxix0 SouT0FaO+nl1oLTDsvPPYlbdzZA== X-Received: from plqu15.prod.google.com ([2002:a17:902:a60f:b0:2ae:c329:bddd]) (user=joonwonkang job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:1ac3:b0:2bd:7ca:e67d with SMTP id d9443c01a7336-2bd07caea66mr18092335ad.29.1778580463897; Tue, 12 May 2026 03:07:43 -0700 (PDT) Date: Tue, 12 May 2026 10:07:42 +0000 In-Reply-To: <20260509171013.GF9285@ziepe.ca> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260509171013.GF9285@ziepe.ca> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260512100742.2522825-1-joonwonkang@google.com> Subject: Re: [PATCH RFC] iommu: Enable per-device SSID space for SVA From: Joonwon Kang To: jgg@ziepe.ca Cc: Alexander.Grest@microsoft.com, amhetre@nvidia.com, baolu.lu@linux.intel.com, easwar.hariharan@linux.microsoft.com, iommu@lists.linux.dev, jacob.jun.pan@linux.intel.com, joonwonkang@google.com, joro@8bytes.org, jpb@kernel.org, kees@kernel.org, kevin.tian@intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, nicolinc@nvidia.com, praan@google.com, robin.murphy@arm.com, smostafa@google.com, will@kernel.org Content-Type: text/plain; charset="UTF-8" > > We have multiple processes and a single device, those processes want to > > do SVA with the same device, and only one process will do SVA with the > > device at a time. Though, the problem occurs even when irrelevant > > processes allocate the PASIDs from the global PASID space for their own > > irrelevant purposes. > > The only way to allocate a PASID from the global PASID space is to > establish another SVA, so you have multiple devices doing SVA? Another way is via iommu_alloc_global_pasid() [1] and it does not require SVA. No, we currently do not have multiple devices doing SVA. But, the problem is that it is out of our control when any device is to allocate a PASID or do SVA for its own purpose. [1] https://lore.kernel.org/all/20230802212427.1497170-3-jacob.jun.pan@linux.intel.com/ Thanks, Joonwon Kang