docs/hypercall-abi: State that the hypercall page is optional

Xen doesn't care (and indeed, cannot feasibly tell) whether a hypercall was initiated using the hypercall page or not. For SEV-SNP/TDX encrypted VMs, use of a hypercall page would violate the integrity properties wanted. Explicitly state that the hypercall page is optional. Signed-off-by: Andrew Cooper <[email protected]> Reviewed-by: Stefano Stabellini <[email protected]>
xen-project · Apr 12, 2024 · c0f890c · c0f890c
1 parent cfb922b
commit c0f890c
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diff --git a/docs/guest-guide/x86/hypercall-abi.rst b/docs/guest-guide/x86/hypercall-abi.rst
@@ -79,7 +79,8 @@ Hypercall Page
 ==============
 
 The hypercall page is a page of guest RAM into which Xen will write suitable
-transfer stubs.
+transfer stubs.  It is intended as a convenience for guests, but use of the
+hypercall page is not mandatory for making hypercalls to Xen.
 
 Creating a hypercall page is an isolated operation from Xen's point of view.
 It is the guests responsibility to ensure that the hypercall page, once