On Sun, May 30, 2021 at 11:06:18AM -0400, Tianyu Lan wrote:

+	if (ms_hyperv.ghcb_base) {
+		rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
+
+		ghcb_va = ioremap_cache(ghcb_gpa, HV_HYP_PAGE_SIZE);
+		if (!ghcb_va)
+			return -ENOMEM;

Can you explain this a bit more?  We've very much deprecated
ioremap_cache in favor of memremap.  Why yo you need a __iomem address
here?  Why do we need the remap here at all?

Does the data structure at this address not have any types that we
could use a struct for?

+
+		rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
+		ghcb_va = ioremap_cache(ghcb_gpa, HV_HYP_PAGE_SIZE);
+		if (!ghcb_va) {

This seems to duplicate the above code.

+bool hv_isolation_type_snp(void)
+{
+	return static_branch_unlikely(&isolation_type_snp);
+}
+EXPORT_SYMBOL_GPL(hv_isolation_type_snp);

This probably wants a kerneldoc explaining when it should be used.