Commit 973df194 authored by Juergen Gross's avatar Juergen Gross Committed by Borislav Petkov (AMD)
Browse files

x86/mtrr: Don't let mtrr_type_lookup() return MTRR_TYPE_INVALID 



mtrr_type_lookup() should always return a valid memory type. In case
there is no information available, it should return the default UC.

This will remove the last case where mtrr_type_lookup() can return
MTRR_TYPE_INVALID, so adjust the comment in include/uapi/asm/mtrr.h.

Note that removing the MTRR_TYPE_INVALID #define from that header
could break user code, so it has to stay.

At the same time the mtrr_type_lookup() stub for the !CONFIG_MTRR
case should set uniform to 1, as if the memory range would be
covered by no MTRR at all.

Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Tested-by: default avatarMichael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20230502120931.20719-15-jgross@suse.com


Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
parent 8227f40a

arch/x86/include/asm/mtrr.h

+5 −2
Original line number Diff line number Diff line
@@ -86,9 +86,12 @@ static inline void mtrr_overwrite_state(struct mtrr_var_range *var, 
static inline u8 mtrr_type_lookup(u64 addr, u64 end, u8 *uniform)

{

	/*

	 * Return no-MTRRs:

	 * Return the default MTRR type, without any known other types in

	 * that range.

	 */

	return MTRR_TYPE_INVALID;

	*uniform = 1;



	return MTRR_TYPE_UNCACHABLE;

}

#define mtrr_save_fixed_ranges(arg) do {} while (0)

#define mtrr_save_state() do {} while (0)

arch/x86/include/uapi/asm/mtrr.h

+3 −3
Original line number Diff line number Diff line
@@ -107,9 +107,9 @@ typedef __u8 mtrr_type; 
#define MTRR_NUM_TYPES       7



/*

 * Invalid MTRR memory type.  mtrr_type_lookup() returns this value when

 * MTRRs are disabled.  Note, this value is allocated from the reserved

 * values (0x7-0xff) of the MTRR memory types.

 * Invalid MTRR memory type.  No longer used outside of MTRR code.

 * Note, this value is allocated from the reserved values (0x7-0xff) of

 * the MTRR memory types.

 */

#define MTRR_TYPE_INVALID    0xff

arch/x86/kernel/cpu/mtrr/generic.c

+2 −2
Original line number Diff line number Diff line
@@ -508,13 +508,13 @@ u8 mtrr_type_lookup(u64 start, u64 end, u8 *uniform) 
	if (!mtrr_state_set) {

		/* Uniformity is unknown. */

		*uniform = 0;

		return MTRR_TYPE_INVALID;

		return MTRR_TYPE_UNCACHABLE;

	}



	*uniform = 1;



	if (!(mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED))

		return MTRR_TYPE_INVALID;

		return MTRR_TYPE_UNCACHABLE;



	for (i = 0; i < cache_map_n && start < end; i++) {

		/* Region after current map entry? -> continue with next one. */