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[142.162.112.119]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8cbbf71ac86sm1260829385a.40.2026.03.02.15.57.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Mar 2026 15:57:16 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vxD8V-00000003wco-2EQO; Mon, 02 Mar 2026 19:57:15 -0400 Date: Mon, 2 Mar 2026 19:57:15 -0400 From: Jason Gunthorpe To: Ankit Soni Cc: iommu@lists.linux.dev, vasant.hegde@amd.com, suravee.suthikulpanit@amd.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] iommu/amd: Adhere to IVINFO[VASIZE] for address limits Message-ID: <20260302235715.GY44359@ziepe.ca> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Feb 27, 2026 at 04:58:04PM +0000, Ankit Soni wrote: > +static u8 ivinfo_vasize_bits(void) > +{ > + u8 vasize; > + > + vasize = FIELD_GET(IOMMU_IVINFO_VASIZE, amd_iommu_ivinfo); > + > + /* > + * IVINFO[VASIZE] encodes the log2 of the maximum virtual address > + * processed by the IOMMU. > + */ > + switch (vasize) { > + case 32: > + case 40: > + case 48: > + case 64: > + return vasize; > + default: > + pr_warn_once("IVRS: IVINFO[VASIZE]=0x%x is invalid, defaulting to 64‑bit VA\n", > + vasize); > + return 64; Why check and limit it like this? > - cfg.common.hw_max_vasz_lg2 = > - min(64, (amd_iommu_hpt_level - 1) * 9 + 21); > + cfg.common.hw_max_vasz_lg2 = amd_iommu_hpt_vasize; This has no restriction, you can send it whatever size you want. Shouldn't the v2 side respect this too? If there is some reason why not it would be good to include it in a comment. Jason