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X-CSE-ConnectionGUID: T+U8qq7TRuWrnmmGsl/GhA== X-CSE-MsgGUID: LZZBvK/kScK+W9MJN5bMvQ== X-IronPort-AV: E=McAfee;i="6800,10657,11778"; a="89785041" X-IronPort-AV: E=Sophos;i="6.23,221,1770624000"; d="scan'208";a="89785041" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2026 02:05:15 -0700 X-CSE-ConnectionGUID: 21NdPKWYTEK3fWqGKg/nUg== X-CSE-MsgGUID: zzXtSJlVSpW4mlIhk4zNPQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,221,1770624000"; d="scan'208";a="231865139" Received: from blu2-mobl.ccr.corp.intel.com (HELO [10.124.248.249]) ([10.124.248.249]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2026 02:05:10 -0700 Message-ID: Date: Thu, 7 May 2026 17:05:07 +0800 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: baolu.lu@linux.intel.com, Robin Murphy , Kevin Tian , Alex Williamson , Shuah Khan , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Saeed Mahameed , Adithya Jayachandran , Parav Pandit , Leon Romanovsky , William Tu , Pratyush Yadav , Pasha Tatashin , David Matlack , Andrew Morton , Chris Li , Pranjal Shrivastava , Vipin Sharma , YiFei Zhu Subject: Re: [PATCH v2 09/16] iommu/vt-d: Restore IOMMU state and reclaimed domain ids To: Samiullah Khawaja , David Woodhouse , Joerg Roedel , Will Deacon , Jason Gunthorpe References: <20260427175633.1978233-1-skhawaja@google.com> <20260427175633.1978233-10-skhawaja@google.com> Content-Language: en-US From: Baolu Lu In-Reply-To: <20260427175633.1978233-10-skhawaja@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/28/2026 1:56 AM, Samiullah Khawaja wrote: > During boot fetch the preserved state of IOMMU unit and if found then > restore the state. > > - Reuse the root_table that was preserved in the previous kernel. > - Reclaim the domain ids of the preserved domains for each preserved > devices so these are not acquired by another domain. > > Signed-off-by: Samiullah Khawaja > --- > drivers/iommu/intel/iommu.c | 55 ++++++++++++++++++++++-------- > drivers/iommu/intel/iommu.h | 7 ++++ > drivers/iommu/intel/liveupdate.c | 57 ++++++++++++++++++++++++++++++++ > 3 files changed, 105 insertions(+), 14 deletions(-) > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c > index 68fecd4e57fa..4118a0861f38 100644 > --- a/drivers/iommu/intel/iommu.c > +++ b/drivers/iommu/intel/iommu.c > @@ -670,10 +670,17 @@ void dmar_fault_dump_ptes(struct intel_iommu *iommu, u16 source_id, > #endif > > /* iommu handling */ > -static int iommu_alloc_root_entry(struct intel_iommu *iommu) > +static int iommu_alloc_root_entry(struct intel_iommu *iommu, > + struct iommu_hw_ser *iommu_ser) > { > struct root_entry *root; > > + if (iommu_ser) { > + intel_iommu_liveupdate_restore_root_table(iommu, iommu_ser); > + __iommu_flush_cache(iommu, iommu->root_entry, ROOT_SIZE); The root table is already active and being used by the hardware at this point, correct? Since the CPU should not be modifying an active table, the __iommu_flush_cache() call seems unnecessary and potentially risky. Furthermore, if the iommu state has been restored, is it necessary to call iommu_set_root_entry()? Calling it would essentially replace an active, in-use root table with an identical one, which appears redundant. > + return 0; > + } > + > root = iommu_alloc_pages_node_sz(iommu->node, GFP_ATOMIC, SZ_4K); > if (!root) { > pr_err("Allocating root entry for %s failed\n", Thanks, baolu