Re: [PATCH] arm: flush: check if the folio is reserved for IMO addresses

[Kefeng Wang]

On 2024/2/22 22:38, Russell King (Oracle) wrote:
> On Thu, Feb 22, 2024 at 10:06:04PM +0800, Kefeng Wang wrote:
> > On 2024/2/22 22:01, Yongqiang Liu wrote:
> > > Since commit a4d5613c4dc6 ("arm: extend pfn_valid to take into account
> > > freed memory map alignment") changes the semantics of pfn_valid() to check
> > > presence of the memory map for a PFN. A valid page for an address which
> > > is reserved but not mapped by the kernel[1].In Some uio case we will get
> > > a crash on a system with the following memory layout:
> > >
> > >    node   0: [mem 0x00000000c0a00000-0x00000000cc8fffff]
> > >    node   0: [mem 0x00000000d0000000-0x00000000da1fffff]
> > >    the uio layout is：0xc0900000, 0x100000
> > >
> > > the crash backtrace like:
> > >
> > >     Unable to handle kernel paging request at virtual address bff00000
> > >     [...]
> > >     CPU: 1 PID: 465 Comm: startapp.bin Tainted: G           O      5.10.0 #1
> > >     Hardware name: Generic DT based system
> > >     PC is at b15_flush_kern_dcache_area+0x24/0x3c
> > >     LR is at __sync_icache_dcache+0x6c/0x98
> > >     [...]
> > >      (b15_flush_kern_dcache_area) from (__sync_icache_dcache+0x6c/0x98)
> > >      (__sync_icache_dcache) from (set_pte_at+0x28/0x54)
> > >      (set_pte_at) from (remap_pfn_range+0x1a0/0x274)
> > >      (remap_pfn_range) from (uio_mmap+0x184/0x1b8 [uio])
> > >      (uio_mmap [uio]) from (__mmap_region+0x264/0x5f4)
> > >      (__mmap_region) from (__do_mmap_mm+0x3ec/0x440)
> > >      (__do_mmap_mm) from (do_mmap+0x50/0x58)
> > >      (do_mmap) from (vm_mmap_pgoff+0xfc/0x188)
> > >      (vm_mmap_pgoff) from (ksys_mmap_pgoff+0xac/0xc4)
> > >      (ksys_mmap_pgoff) from (ret_fast_syscall+0x0/0x5c)
> > >     Code: e0801001 e2423001 e1c00003 f57ff04f (ee070f3e)
> > >     ---[ end trace 09cf0734c3805d52 ]---
> > >     Kernel panic - not syncing: Fatal exception
> > >
> > > So check if PG_reserved was set to solve this issue.
> > >
> > > [1]: https://lore.kernel.org/lkml/Zbtdue57RO0QScJM@xxxxxxxxxxxxx/
> > >
> > > Fixes: a4d5613c4dc6 ("arm: extend pfn_valid to take into account freed memory map alignment")
> > > Suggested-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> > > Signed-off-by: Yongqiang Liu <liuyongqiang13@xxxxxxxxxx>
> > > ---
> > >    arch/arm/mm/flush.c | 4 ++++
> > >    1 file changed, 4 insertions(+)
> > >
> > > diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
> > > index d19d140a10c7..f2b99223a0ab 100644
> > > --- a/arch/arm/mm/flush.c
> > > +++ b/arch/arm/mm/flush.c
> > > @@ -15,6 +15,7 @@
> > >    #include <asm/smp_plat.h>
> > >    #include <asm/tlbflush.h>
> > >    #include <linux/hugetlb.h>
> > > +#include <linux/memblock.h>
> > 这个删掉吧然后发出去
>
> Speak English so that everyone knows what you are saying. You are
> participating in an international community where English is the
> language that we use to communicate between ourselves.
Sorry, I mistake for a internal mail

To Yongqiang, please drop the unnecessary include and as Matthew said,
please consider to use folio helper.

> Thanks.