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

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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: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20230502120931.20719-15-jgross@suse.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
This commit is contained in:
Juergen Gross 2023-05-02 14:09:29 +02:00 • committed by Borislav Petkov (AMD)
parent 8227f40ade
commit 973df19420
3 changed files with 10 additions and 7 deletions
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7
arch/x86/include/asm/mtrr.h
View file

@ -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)

6
arch/x86/include/uapi/asm/mtrr.h
View file

@ -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

4
arch/x86/kernel/cpu/mtrr/generic.c
View file

@ -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. */