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

From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Mike Rapoport <rppt@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Andy Lutomirski <luto@kernel.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Borislav Petkov <bp@alien8.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Christoph Lameter <cl@linux.com>,
	"David S. Miller" <davem@davemloft.net>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	David Hildenbrand <david@redhat.com>,
	David Rientjes <rientjes@google.com>,
	"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Ingo Molnar <mingo@redhat.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Len Brown <len.brown@intel.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Mackerras <paulus@samba.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Pavel Machek <pavel@ucw.cz>, Pekka Enberg <penberg@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vasily Gorbik <gor@linux.ibm.com>, Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-pm@vger.kernel.org, linux-riscv@lists.infradead.org,
	linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	sparclinux@vger.kernel.org, x86@kernel.org,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Subject: Re: [PATCH v3 2/4] PM: hibernate: make direct map manipulations more explicit
Date: Tue, 3 Nov 2020 17:39:16 +0300	[thread overview]
Message-ID: <20201103143916.otz2o4h2dlmewn3h@box> (raw)
In-Reply-To: <20201103121350.GI4879@kernel.org>

On Tue, Nov 03, 2020 at 02:13:50PM +0200, Mike Rapoport wrote:
> 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.

pr_warn_once()? :P

-- 
 Kirill A. Shutemov