x86/coco: Add API to handle encryption mask

AMD SME/SEV uses a bit in the page table entries to indicate that the
page is encrypted and not accessible to the VMM.

TDX uses a similar approach, but the polarity of the mask is opposite to
AMD: if the bit is set the page is accessible to VMM.

Provide vendor-neutral API to deal with the mask: cc_mkenc() and
cc_mkdec() modify given address to make it encrypted/decrypted. It can
be applied to phys_addr_t, pgprotval_t or page table entry value.

pgprot_encrypted() and pgprot_decrypted() reimplemented using new
helpers.

The implementation will be extended to cover TDX.

pgprot_decrypted() is used by drivers (i915, virtio_gpu, vfio).
cc_mkdec() called by pgprot_decrypted(). Export cc_mkdec().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20220222185740.26228-5-kirill.shutemov@linux.intel.com

1 files changed, 27 insertions, 0 deletions

diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index 476dcd198af5..fc1365dd927e 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -14,6 +14,7 @@
 #include <asm/processor.h>
 
 static enum cc_vendor vendor __ro_after_init;
+static u64 cc_mask __ro_after_init;
 
 static bool intel_cc_platform_has(enum cc_attr attr)
 {
@@ -84,7 +85,33 @@ bool cc_platform_has(enum cc_attr attr)
 }
 EXPORT_SYMBOL_GPL(cc_platform_has);
 
+u64 cc_mkenc(u64 val)
+{
+	switch (vendor) {
+	case CC_VENDOR_AMD:
+		return val | cc_mask;
+	default:
+		return val;
+	}
+}
+
+u64 cc_mkdec(u64 val)
+{
+	switch (vendor) {
+	case CC_VENDOR_AMD:
+		return val & ~cc_mask;
+	default:
+		return val;
+	}
+}
+EXPORT_SYMBOL_GPL(cc_mkdec);
+
 __init void cc_set_vendor(enum cc_vendor v)
 {
 	vendor = v;
 }
+
+__init void cc_set_mask(u64 mask)
+{
+	cc_mask = mask;
+}