On Tue, Jun 24, 2025 at 02:01:48PM -0700, Dave Hansen wrote:
Changes from v1:
- Fix minor typos
- Use the more generic and standard ex_handler_default(). Had the original code used this helper, the bug would not have been there in the first place.
Doesn't this here typically go under the --- with the diffstat etc?
--
From: Dave Hansen dave.hansen@linux.intel.com
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().
Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Fixes: d5c8028b4788 ("x86/fpu: Reinitialize FPU registers if restoring FPU state fails") Acked-by: Alison Schofield alison.schofield@intel.com Cc: stable@vger.kernel.org Cc: Eric Biggers ebiggers@google.com Cc: Rik van Riel riel@redhat.com Cc: Borislav Petkov bp@alien8.de Cc: Chang S. Bae chang.seok.bae@intel.com
Acked-by: Peter Zijlstra (Intel) peterz@infradead.org