On 8/19/21 4:52 AM, Christoph Hellwig wrote:

On Fri, Aug 13, 2021 at 11:59:22AM -0500, Tom Lendacky wrote:

quoted

While the name suggests this is intended mainly for guests, it will
also be used for host memory encryption checks in place of sme_active().

Which suggest that the name is not good to start with.  Maybe protected
hardware, system or platform might be a better choice?

quoted

+static inline bool prot_guest_has(unsigned int attr)
+{
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+	if (sme_me_mask)
+		return amd_prot_guest_has(attr);
+#endif
+
+	return false;
+}

Shouldn't this be entirely out of line?

I did it as inline originally because the presence of the function will be
decided based on the ARCH_HAS_PROTECTED_GUEST config. For now, that is
only selected by the AMD memory encryption support, so if I went out of
line I could put in mem_encrypt.c. But with TDX wanting to also use it, it
would have to be in an always built file with some #ifdefs or in its own
file that is conditionally built based on the ARCH_HAS_PROTECTED_GUEST
setting (they've already tried building with ARCH_HAS_PROTECTED_GUEST=y
and AMD_MEM_ENCRYPT not set).

To take it out of line, I'm leaning towards the latter, creating a new
file that is built based on the ARCH_HAS_PROTECTED_GUEST setting.

quoted

+/* 0x800 - 0x8ff reserved for AMD */
+#define PATTR_SME			0x800
+#define PATTR_SEV			0x801
+#define PATTR_SEV_ES			0x802

Why do we need reservations for a purely in-kernel namespace?

And why are you overoading a brand new generic API with weird details
of a specific implementation like this?

There was some talk about this on the mailing list where TDX and SEV may
need to be differentiated, so we wanted to reserve a range of values per
technology. I guess I can remove them until they are actually needed.

Thanks,
Tom