linux-kernel - Re: [PATCH v3 2/4] PM: hibernate: make direct map manipulations more explicit

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Message-ID: <20201103121350.GI4879@kernel.org>
Date:   Tue, 3 Nov 2020 14:13:50 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andy Lutomirski <luto@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Christoph Lameter <cl@...ux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Len Brown <len.brown@...el.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Pavel Machek <pavel@....cz>, Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-pm@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
        x86@...nel.org, "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v3 2/4] PM: hibernate: make direct map manipulations more
 explicit

On Tue, Nov 03, 2020 at 02:08:16PM +0300, Kirill A. Shutemov wrote:
> On Sun, Nov 01, 2020 at 07:08:13PM +0200, Mike Rapoport wrote:
> > diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> > index 46b1804c1ddf..054c8cce4236 100644
> > --- a/kernel/power/snapshot.c
> > +++ b/kernel/power/snapshot.c
> > @@ -76,6 +76,32 @@ static inline void hibernate_restore_protect_page(void *page_address) {}
> >  static inline void hibernate_restore_unprotect_page(void *page_address) {}
> >  #endif /* CONFIG_STRICT_KERNEL_RWX  && CONFIG_ARCH_HAS_SET_MEMORY */
> >  
> > +static inline void hibernate_map_page(struct page *page, int enable)
> > +{
> > +	if (IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) {
> > +		unsigned long addr = (unsigned long)page_address(page);
> > +		int ret;
> > +
> > +		/*
> > +		 * This should not fail because remapping a page here means
> > +		 * that we only update protection bits in an existing PTE.
> > +		 * It is still worth to have WARN_ON() here if something
> > +		 * changes and this will no longer be the case.
> > +		 */
> > +		if (enable)
> > +			ret = set_direct_map_default_noflush(page);
> > +		else
> > +			ret = set_direct_map_invalid_noflush(page);
> > +
> > +		if (WARN_ON(ret))
> 
> _ONCE?

I've changed it to pr_warn() after David said people enable panic on
warn in production kernels.

> > +			return;
> > +
> > +		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
> > +	} else {
> > +		debug_pagealloc_map_pages(page, 1, enable);
> > +	}
> > +}
> > +
> >  static int swsusp_page_is_free(struct page *);
> >  static void swsusp_set_page_forbidden(struct page *);
> >  static void swsusp_unset_page_forbidden(struct page *);
> 
> -- 
>  Kirill A. Shutemov

-- 
Sincerely yours,
Mike.