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Mon, 31 Mar 2025 22:57:45 -0700 (PDT) Message-ID: <7ed9418b-db12-4678-bf7a-634daf66282d@suse.com> Date: Tue, 1 Apr 2025 08:57:44 +0300 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/ioremap: Maintain consistent IORES_MAP_ENCRYPTED for BIOS data To: Dan Williams , dave.hansen@linux.intel.com Cc: x86@kernel.org, Vishal Annapurve , Kirill Shutemov , stable@vger.kernel.org, linux-coco@lists.linux.dev References: <174346288005.2166708.14425674491111625620.stgit@dwillia2-xfh.jf.intel.com> Content-Language: en-US From: Nikolay Borisov In-Reply-To: <174346288005.2166708.14425674491111625620.stgit@dwillia2-xfh.jf.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 1.04.25 г. 2:14 ч., Dan Williams wrote: > Nikolay reports [1] that accessing BIOS data (first 1MB of the physical > address space) via /dev/mem results in an SEPT violation. > > The cause is ioremap() (via xlate_dev_mem_ptr()) establishing an > unencrypted mapping where the kernel had established an encrypted > mapping previously. > > Teach __ioremap_check_other() that this address space shall always be > mapped as encrypted as historically it is memory resident data, not MMIO > with side-effects. > > Cc: > Cc: Vishal Annapurve > Cc: Kirill Shutemov > Reported-by: Nikolay Borisov > Closes: http://lore.kernel.org/20250318113604.297726-1-nik.borisov@suse.com [1] > Tested-by: Nikolay Borisov > Fixes: 9aa6ea69852c ("x86/tdx: Make pages shared in ioremap()") > Cc: > Signed-off-by: Dan Williams Reviewed-by: Nikolay Borisov > --- > arch/x86/mm/ioremap.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c > index 42c90b420773..9e81286a631e 100644 > --- a/arch/x86/mm/ioremap.c > +++ b/arch/x86/mm/ioremap.c > @@ -122,6 +122,10 @@ static void __ioremap_check_other(resource_size_t addr, struct ioremap_desc *des > return; > } > > + /* Ensure BIOS data (see devmem_is_allowed()) is consistently mapped */ > + if (PHYS_PFN(addr) < 256) > + desc->flags |= IORES_MAP_ENCRYPTED; Side question: Is it guaranteed that this region will be mapped with 4k pages and not some larger size? I.e should the 256 constant be dependent on the current page size? > + > if (!IS_ENABLED(CONFIG_EFI)) > return; > >