linux-kernel - Re: [PATCH] mm: hugetlb: fix HVO crash on s390

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Message-ID: <20251028161426.35377Af6-hca@linux.ibm.com>
Date: Tue, 28 Oct 2025 17:14:26 +0100
From: Heiko Carstens <hca@...ux.ibm.com>
To: Joao Martins <joao.m.martins@...cle.com>
Cc: Luiz Capitulino <luizcap@...hat.com>, osalvador@...e.de,
        akpm@...ux-foundation.org, david@...hat.com, aneesh.kumar@...nel.org,
        borntraeger@...ux.ibm.com, mike.kravetz@...cle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH] mm: hugetlb: fix HVO crash on s390

On Tue, Oct 28, 2025 at 04:05:45PM +0000, Joao Martins wrote:
> > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > index ba0fb1b6a5a8..5819a3088850 100644
> > --- a/mm/hugetlb_vmemmap.c
> > +++ b/mm/hugetlb_vmemmap.c
> > @@ -48,6 +48,15 @@ struct vmemmap_remap_walk {
> >  	unsigned long		flags;
> >  };
> >  
> > +static inline void vmemmap_flush_tlb_all(void)
> > +{
> > +#ifdef CONFIG_S390
> > +	__tlb_flush_kernel();
> > +#else
> > +	flush_tlb_all();
> > +#endif
> > +}
> > +
> 
> Wouldn't a better fix be to implement flush_tlb_all() in
> s390/include/asm/tlbflush.h since that aliases to __tlb_flush_kernel()?

The question is rather what is flush_tlb_all() supposed to flush? Is
it supposed to flush only tlb entries corresponding to the kernel
address space, or should it flush just everything?

Within this context it looks like only tlb flushing for the kernel
address space is required(?)