x86/mtrr: Check if fixed-range MTRRs exist in mtrr_save_fixed_ranges()

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[ Upstream commit 824c6384e8 ]

When suspending, save_processor_state() calls mtrr_save_fixed_ranges()
to save fixed-range MTRRs.

On platforms without fixed-range MTRRs like the ACRN hypervisor which
has removed fixed-range MTRR emulation, accessing these MSRs will
trigger an unchecked MSR access error. Make sure fixed-range MTRRs are
supported before access to prevent such error.

Since mtrr_state.have_fixed is only set when MTRRs are present and
enabled, checking the CPU feature flag in mtrr_save_fixed_ranges() is
unnecessary.

Fixes: 3ebad59056 ("[PATCH] x86: Save and restore the fixed-range MTRRs of the BSP when suspending")
Signed-off-by: Jiaqing Zhao <jiaqing.zhao@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250509170633.3411169-2-jiaqing.zhao@linux.intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Jiaqing Zhao 2025-05-09 17:06:33 +00:00 • committed by Greg Kroah-Hartman

parent f551f0e630

commit d3cc08bad4

1 changed files with 1 additions and 1 deletions

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

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