From mboxrd@z Thu Jan 1 00:00:00 1970 From: Randy Dunlap Subject: Re: [PATCH v5 16/16] x86/tdx: Add cmdline option to force use of ioremap_host_shared Date: Fri, 8 Oct 2021 18:45:26 -0700 Message-ID: <7b4c3e3e-09e4-3bf8-6e23-77892fb6df02@infradead.org> References: <20211009003711.1390019-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20211009003711.1390019-17-sathyanarayanan.kuppuswamy@linux.intel.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To: Subject:Sender:Reply-To:Content-ID:Content-Description; bh=8Yhlfpn88xGUZ0D2UsU9ZR1KIwe5CGURq7DLgR1hrBY=; b=1Z6zSdy4U1cnEgkDHFifc+XY8Y GlewY7KjyFBbKH64naXeI41ZeCK2wzbxmLYn8tQReOLUCKAfWokngJdgXzG2kZqfZuukHe0LzGSem /fWn4TtGInc4xujKU9lhTWQmbcOyZPdRobBXzgyYqQiz2V+LCqXMtthT6T+ZQAyQo3oPf9aPdoOkJ XKCfcDJy3GwQcs5wemBALdUGapmhhOQ0Ws+MHquNKSKXMDSnM/RxQhR8WlIXhEXmTBWm/wLd+hHF0 AGJlpBT1b3CurBjVkXBwVF3uizzCjn8R7aZLHlbBj649FMdFXEGzDXcQrpB78Kj/tCgGw8zSXNsVA Vnnceg4Q==; In-Reply-To: <20211009003711.1390019-17-sathyanarayanan.kuppuswamy@linux.intel.com> Content-Language: en-US List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Kuppuswamy Sathyanarayanan , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , Bjorn Helgaas , Richard Henderson , Thomas Bogendoerfer , James E J Bottomley , Helge Deller , "David S . Miller" , Arnd Bergmann , Jonathan Corbet , "Michael S . Tsirkin" , Paolo Bonzini , David Hildenbrand , Andrea Arcangeli , Josh Poimboeuf Cc: Peter H Anvin , Dave Hansen , Tony Luck , Dan Williams , Andi Kleen , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , x86@kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, virtualization@lists.linux-foundation.org On 10/8/21 5:37 PM, Kuppuswamy Sathyanarayanan wrote: > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 91ba391f9b32..0af19cb1a28c 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2076,6 +2076,18 @@ > 1 - Bypass the IOMMU for DMA. > unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. > > + ioremap_force_shared= [X86_64, CCG] > + Force the kernel to use shared memory mappings which do > + not use ioremap_host_shared/pcimap_host_shared to opt-in > + to shared mappings with the host. This feature is mainly > + used by a confidential guest when enabling new drivers > + without proper shared memory related changes. Please note > + that this option might also allow other non explicitly > + enabled drivers to interact with the host in confidential > + guest, which could cause other security risks. This option > + will also cause BIOS data structures to be shared with the > + host, which might open security holes. Hi, This cmdline option text should have a little bit more info. Just as an example/template: acpi_apic_instance= [ACPI, IOAPIC] Format: 2: use 2nd APIC table, if available 1,0: use 1st APIC table default: 0 So what is expected after the "=" sign?... thanks. -- ~Randy