On Tue, Jan 08, 2019 at 11:24:43AM +0800, Miles Chen wrote: > On Mon, 2019-01-07 at 15:00 +0000, Mark Rutland wrote: > > On Mon, Jan 07, 2019 at 07:21:20PM +0800, Miles Chen wrote: > > > Current __virt_to_phys() only print warning messages for non-linear > > > addresses. It's hard to catch all warnings by those messages. > > > > Why? Are you seeing a large number of warnings somewhere? > > Official kernel works fine. I saw some cases in our internal branch and > we're fixing them. > > > > > > So add a VIRTUAL_BUG_ON() to trap all non-linear and non-symbol > > > addresses (e.g., stack addresses) > > > > > > Tested by pass stack addresses and symbol addresses to __pa(). Result: > > > stack addresses: kernel BUG() > > > > Either: > > > > * Stacks are vmap'd, and __is_lm_address(stack_addr) is false. We'll > > produce a WARNING() today (and return a junk physical address). > > > > * Stacks are linear mapped, and cannot be distinguished from other > > linear mapped addresses. The physical address will be valid. > > > > ... so I don't understand why you need to change this. > > For the first case: for vmap'd stack, __pa() returns a junk > physical address and it might be easier to debug this incorrect address > translation by a BUG() call instead of monitoring the warning log.
I think that's an argument for upgrading the existing WARN() to a BUG(), rather than adding a separate VIRTUAL_BUG_ON(). However, there are cases where the junk physical address is not used to perform an access, and the WARN() is more helpful. You can set panic_on_warn to get an immediate panic() when the WARN() fires. Is there some reason that approach doesn't work for you? Thanks, Mark.
