linux-kernel - Re: [PATCH 3/3] arm64: kdump: defer the crashkernel reservation for platforms with no DMA memory zones

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Message-ID: <ZCBEQ12AYSrujUBn@MiWiFi-R3L-srv>
Date:   Sun, 26 Mar 2023 21:10:27 +0800
From:   Baoquan He <bhe@...hat.com>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
Cc:     linux-kernel@...r.kernel.org, catalin.marinas@....com,
        horms@...nel.org, John.p.donnelly@...cle.com, will@...nel.org,
        kexec@...ts.infradead.org, ardb@...nel.org, rppt@...nel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/3] arm64: kdump: defer the crashkernel reservation for
 platforms with no DMA memory zones

On 03/25/23 at 10:04am, Leizhen (ThunderTown) wrote:
> 
> 
> On 2023/3/24 21:18, Baoquan He wrote:
> > In commit 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
> > platforms with no DMA memory zones"), reserve_crashkernel() is called
> > much earlier in arm64_memblock_init() to avoid causing base apge
> > mapping on platforms with no DMA meomry zones.
> > 
> > With taking off protection on crashkernel memory region, no need to call
> > reserve_crashkernel() specially in advance. The deferred invocation of
> > reserve_crashkernel() in bootmem_init() can cover all cases.
> > 
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > ---
> >  arch/arm64/include/asm/memory.h | 5 -----
> >  arch/arm64/mm/init.c            | 6 +-----
> >  2 files changed, 1 insertion(+), 10 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> > index 78e5163836a0..efcd68154a3a 100644
> > --- a/arch/arm64/include/asm/memory.h
> > +++ b/arch/arm64/include/asm/memory.h
> > @@ -374,11 +374,6 @@ static inline void *phys_to_virt(phys_addr_t x)
> >  })
> >  
> >  void dump_mem_limit(void);
> > -
> > -static inline bool defer_reserve_crashkernel(void)
> > -{
> > -	return IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32);
> > -}
> >  #endif /* !ASSEMBLY */
> >  
> >  /*
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 58a0bb2c17f1..b888de59e0b7 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -408,9 +408,6 @@ void __init arm64_memblock_init(void)
> >  
> >  	early_init_fdt_scan_reserved_mem();
> >  
> > -	if (!defer_reserve_crashkernel())
> > -		reserve_crashkernel();
> > -
> >  	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
> >  }
> >  
> > @@ -457,8 +454,7 @@ void __init bootmem_init(void)
> >  	 * request_standard_resources() depends on crashkernel's memory being
> >  	 * reserved, so do it here.
> >  	 */
> > -	if (defer_reserve_crashkernel())
> > -		reserve_crashkernel();
> > +	reserve_crashkernel();
> >  
> >  	memblock_dump_all();
> >  }
> 
> Some comments also need to be deleted, above the definition of arm64_dma_phys_limit
> in arch/arm64/mm/init.c

Thanks, have posted v2 of patch 3 to remove the code comment, and move
back the arm64_dma_phys_limit assignmet as 'PHYS_MASK + 1;' into
zone_sizes_init(). These should be part of the reverting commit
031495635b46, I missed that.