Re: [PATCH v5 16/16] x86/tdx: Add cmdline option to force use of ioremap_host_shared | virtualization

(off-list ancestor, not in this archive)

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: <int>
			2: use 2nd APIC table, if available
			1,0: use 1st APIC table
			default: 0

So what is expected after the "=" sign?...

thanks.
-- 
~Randy
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