The following commit has been merged into the x86/fpu branch of tip:

Commit-ID: 1cec9ac2d071cfd2da562241aab0ef701355762a Gitweb: https://git.kernel.org/tip/1cec9ac2d071cfd2da562241aab0ef701355762a Author: Dave Hansen dave.hansen@linux.intel.com AuthorDate: Tue, 24 Jun 2025 14:01:48 -07:00 Committer: Dave Hansen dave.hansen@linux.intel.com CommitterDate: Wed, 25 Jun 2025 16:28:06 -07:00

x86/fpu: Delay instruction pointer fixup until after warning

Right now, if XRSTOR fails a console message like this is be printed:

Bad FPU state detected at restore_fpregs_from_fpstate+0x9a/0x170, reinitializing FPU registers.

However, the text location (...+0x9a in this case) is the instruction *AFTER* the XRSTOR. The highlighted instruction in the "Code:" dump also points one instruction late.

The reason is that the "fixup" moves RIP up to pass the bad XRSTOR and keep on running after returning from the #GP handler. But it does this fixup before warning.

The resulting warning output is nonsensical because it looks like the non-FPU-related instruction is #GP'ing.

Do not fix up RIP until after printing the warning. Do this by using the more generic and standard ex_handler_default().

Fixes: d5c8028b4788 ("x86/fpu: Reinitialize FPU registers if restoring FPU state fails") Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Reviewed-by: Chao Gao chao.gao@intel.com Acked-by: Alison Schofield alison.schofield@intel.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc:stable@vger.kernel.org Link: https://lore.kernel.org/all/20250624210148.97126F9E%40davehans-spike.ostc.in... --- arch/x86/mm/extable.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c index bf8dab1..2fdc1f1 100644 --- a/arch/x86/mm/extable.c +++ b/arch/x86/mm/extable.c @@ -122,13 +122,12 @@ static bool ex_handler_sgx(const struct exception_table_entry *fixup, static bool ex_handler_fprestore(const struct exception_table_entry *fixup, struct pt_regs *regs) { - regs->ip = ex_fixup_addr(fixup); - WARN_ONCE(1, "Bad FPU state detected at %pB, reinitializing FPU registers.", (void *)instruction_pointer(regs));

fpu_reset_from_exception_fixup(); - return true; + + return ex_handler_default(fixup, regs); }

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