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Date: Sun, 14 Feb 2021 11:19:54 +0200
From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
Message-ID: <20210214091954.GM242749@kernel.org>
References: <YCJMDBss8Qhha7g9@dhcp22.suse.cz>
 <20210209090938.GP299309@linux.ibm.com>
 <YCKLVzBR62+NtvyF@dhcp22.suse.cz>
 <20210211071319.GF242749@kernel.org>
 <YCTtSrCEvuBug2ap@dhcp22.suse.cz>
 <0d66baec-1898-987b-7eaf-68a015c027ff@redhat.com>
 <20210211112702.GI242749@kernel.org>
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CC: Michal Hocko <mhocko@suse.com>, Mike Rapoport <rppt@linux.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>, Catalin Marinas <catalin.marinas@arm.com>, Christopher Lameter <cl@linux.com>, Dave Hansen <dave.hansen@linux.intel.com>, Elena Reshetova <elena.reshetova@intel.com>, "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>, James Bottomley <jejb@linux.ibm.com>, "Kirill A. Shutemov" <kirill@shutemov.name>, Matthew Wilcox <willy@infradead.org>, Mark Rutland <mark.rutland@arm.com>, Michael Kerrisk <mtk.manpages@gmail.com>, Palmer Dabbelt <palmer@dabbelt.com>, Paul Walmsley <paul.walmsley@sifive.com>, Peter Zijlstra <peterz@infradead.org>, Rick Edgecombe <rick.p.edgecombe@intel.com>, Roman Gushchin <guro@fb.com>, Shakeel Butt <shakeelb@google.com>, Shuah Khan <shuah@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Tycho Anders
 en <tycho@tycho.ws>, Will Deacon <will@kernel.org>, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org, Hagen Paul Pfeifer <hagen@jauu.net>, Palmer Dabbelt <palmerdabbelt@google.com>
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On Fri, Feb 12, 2021 at 10:18:19AM +0100, David Hildenbrand wrote:
> On 12.02.21 00:09, Mike Rapoport wrote:
> > On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote:
> > > On 11.02.21 12:27, Mike Rapoport wrote:
> > > > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote:
> > > 
> > > So let's talk about the main user-visible differences to other memfd files
> > > (especially, other purely virtual files like hugetlbfs). With secretmem:
> > > 
> > > - File content can only be read/written via memory mappings.
> > > - File content cannot be swapped out.
> > > 
> > > I think there are still valid ways to modify file content using syscalls:
> > > e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just
> > > fine.
> > These work perfectly with any file, so maybe we should have added
> > memfd_create as a flag to open(2) back then and now the secretmem file
> > descriptors?
> 
> I think open() vs memfd_create() makes sense: for open, the path specifies
> main properties (tmpfs, hugetlbfs, filesystem). On memfd, there is no such
> path and the "type" has to be specified differently.
> 
> Also, open() might open existing files - memfd always creates new files.

Yes, but still open() returns a handle to a file and memfd_create() returns
a handle to a file. The differences may be well hidden by e.g. O_MEMORY and
than features unique to memfd files will have their set of O_SOMETHING
flags.

It's the same logic that says "we already have an interface that's close
enough and it's fine to add a bunch of new flags there".
 
And here we come to the question "what are the differences that justify a
new system call?" and the answer to this is very subjective. And as such we
can continue bikeshedding forever.

-- 
Sincerely yours,
Mike.
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
To unsubscribe send an email to linux-nvdimm-leave@lists.01.org

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Date:   Sun, 14 Feb 2021 11:19:54 +0200
From:   Mike Rapoport <rppt@kernel.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     Michal Hocko <mhocko@suse.com>, Mike Rapoport <rppt@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Christopher Lameter <cl@linux.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Elena Reshetova <elena.reshetova@intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        James Bottomley <jejb@linux.ibm.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Matthew Wilcox <willy@infradead.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Roman Gushchin <guro@fb.com>,
        Shakeel Butt <shakeelb@google.com>,
        Shuah Khan <shuah@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tycho Andersen <tycho@tycho.ws>, Will Deacon <will@kernel.org>,
        linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org,
        x86@kernel.org, Hagen Paul Pfeifer <hagen@jauu.net>,
        Palmer Dabbelt <palmerdabbelt@google.com>
Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
Message-ID: <20210214091954.GM242749@kernel.org>
References: <YCJMDBss8Qhha7g9@dhcp22.suse.cz>
 <20210209090938.GP299309@linux.ibm.com>
 <YCKLVzBR62+NtvyF@dhcp22.suse.cz>
 <20210211071319.GF242749@kernel.org>
 <YCTtSrCEvuBug2ap@dhcp22.suse.cz>
 <0d66baec-1898-987b-7eaf-68a015c027ff@redhat.com>
 <20210211112702.GI242749@kernel.org>
 <05082284-bd85-579f-2b3e-9b1af663eb6f@redhat.com>
 <20210211230910.GL242749@kernel.org>
 <a903338e-3d56-ff0a-4f4f-0f23db7ec0da@redhat.com>
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On Fri, Feb 12, 2021 at 10:18:19AM +0100, David Hildenbrand wrote:
> On 12.02.21 00:09, Mike Rapoport wrote:
> > On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote:
> > > On 11.02.21 12:27, Mike Rapoport wrote:
> > > > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote:
> > > 
> > > So let's talk about the main user-visible differences to other memfd files
> > > (especially, other purely virtual files like hugetlbfs). With secretmem:
> > > 
> > > - File content can only be read/written via memory mappings.
> > > - File content cannot be swapped out.
> > > 
> > > I think there are still valid ways to modify file content using syscalls:
> > > e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just
> > > fine.
> > These work perfectly with any file, so maybe we should have added
> > memfd_create as a flag to open(2) back then and now the secretmem file
> > descriptors?
> 
> I think open() vs memfd_create() makes sense: for open, the path specifies
> main properties (tmpfs, hugetlbfs, filesystem). On memfd, there is no such
> path and the "type" has to be specified differently.
> 
> Also, open() might open existing files - memfd always creates new files.

Yes, but still open() returns a handle to a file and memfd_create() returns
a handle to a file. The differences may be well hidden by e.g. O_MEMORY and
than features unique to memfd files will have their set of O_SOMETHING
flags.

It's the same logic that says "we already have an interface that's close
enough and it's fine to add a bunch of new flags there".
 
And here we come to the question "what are the differences that justify a
new system call?" and the answer to this is very subjective. And as such we
can continue bikeshedding forever.

-- 
Sincerely yours,
Mike.

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Sun, 14 Feb 2021 11:19:54 +0200
From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
Message-ID: <20210214091954.GM242749@kernel.org>
References: <YCJMDBss8Qhha7g9@dhcp22.suse.cz>
 <20210209090938.GP299309@linux.ibm.com>
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 <YCTtSrCEvuBug2ap@dhcp22.suse.cz>
 <0d66baec-1898-987b-7eaf-68a015c027ff@redhat.com>
 <20210211112702.GI242749@kernel.org>
 <05082284-bd85-579f-2b3e-9b1af663eb6f@redhat.com>
 <20210211230910.GL242749@kernel.org>
 <a903338e-3d56-ff0a-4f4f-0f23db7ec0da@redhat.com>
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Cc: Mark Rutland <mark.rutland@arm.com>, Michal Hocko <mhocko@suse.com>,
 Peter Zijlstra <peterz@infradead.org>,
 Catalin Marinas <catalin.marinas@arm.com>,
 Dave Hansen <dave.hansen@linux.intel.com>, linux-mm@kvack.org,
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 Christopher Lameter <cl@linux.com>, Shuah Khan <shuah@kernel.org>,
 Thomas Gleixner <tglx@linutronix.de>,
 Elena Reshetova <elena.reshetova@intel.com>, linux-arch@vger.kernel.org,
 Tycho Andersen <tycho@tycho.ws>, linux-nvdimm@lists.01.org,
 Will Deacon <will@kernel.org>, x86@kernel.org,
 Matthew Wilcox <willy@infradead.org>, Mike Rapoport <rppt@linux.ibm.com>,
 Ingo Molnar <mingo@redhat.com>, Michael Kerrisk <mtk.manpages@gmail.com>,
 Palmer Dabbelt <palmerdabbelt@google.com>, Arnd Bergmann <arnd@arndb.de>,
 James Bottomley <jejb@linux.ibm.com>, Hagen Paul Pfeifer <hagen@jauu.net>,
 Borislav Petkov <bp@alien8.de>, Alexander Viro <viro@zeniv.linux.org.uk>,
 Andy Lutomirski <luto@kernel.org>, Paul Walmsley <paul.walmsley@sifive.com>,
 "Kirill A. Shutemov" <kirill@shutemov.name>,
 Dan Williams <dan.j.williams@intel.com>, linux-arm-kernel@lists.infradead.org,
 linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
 linux-riscv@lists.infradead.org, Palmer Dabbelt <palmer@dabbelt.com>,
 linux-fsdevel@vger.kernel.org, Shakeel Butt <shakeelb@google.com>,
 Andrew Morton <akpm@linux-foundation.org>,
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On Fri, Feb 12, 2021 at 10:18:19AM +0100, David Hildenbrand wrote:
> On 12.02.21 00:09, Mike Rapoport wrote:
> > On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote:
> > > On 11.02.21 12:27, Mike Rapoport wrote:
> > > > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote:
> > > 
> > > So let's talk about the main user-visible differences to other memfd files
> > > (especially, other purely virtual files like hugetlbfs). With secretmem:
> > > 
> > > - File content can only be read/written via memory mappings.
> > > - File content cannot be swapped out.
> > > 
> > > I think there are still valid ways to modify file content using syscalls:
> > > e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just
> > > fine.
> > These work perfectly with any file, so maybe we should have added
> > memfd_create as a flag to open(2) back then and now the secretmem file
> > descriptors?
> 
> I think open() vs memfd_create() makes sense: for open, the path specifies
> main properties (tmpfs, hugetlbfs, filesystem). On memfd, there is no such
> path and the "type" has to be specified differently.
> 
> Also, open() might open existing files - memfd always creates new files.

Yes, but still open() returns a handle to a file and memfd_create() returns
a handle to a file. The differences may be well hidden by e.g. O_MEMORY and
than features unique to memfd files will have their set of O_SOMETHING
flags.

It's the same logic that says "we already have an interface that's close
enough and it's fine to add a bunch of new flags there".
 
And here we come to the question "what are the differences that justify a
new system call?" and the answer to this is very subjective. And as such we
can continue bikeshedding forever.

-- 
Sincerely yours,
Mike.

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

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Date: Sun, 14 Feb 2021 11:19:54 +0200
From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
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Cc: Mark Rutland <mark.rutland@arm.com>, Michal Hocko <mhocko@suse.com>,
 Peter Zijlstra <peterz@infradead.org>,
 Catalin Marinas <catalin.marinas@arm.com>,
 Dave Hansen <dave.hansen@linux.intel.com>, linux-mm@kvack.org,
 linux-kselftest@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
 Christopher Lameter <cl@linux.com>, Shuah Khan <shuah@kernel.org>,
 Thomas Gleixner <tglx@linutronix.de>,
 Elena Reshetova <elena.reshetova@intel.com>, linux-arch@vger.kernel.org,
 Tycho Andersen <tycho@tycho.ws>, linux-nvdimm@lists.01.org,
 Will Deacon <will@kernel.org>, x86@kernel.org,
 Matthew Wilcox <willy@infradead.org>, Mike Rapoport <rppt@linux.ibm.com>,
 Ingo Molnar <mingo@redhat.com>, Michael Kerrisk <mtk.manpages@gmail.com>,
 Palmer Dabbelt <palmerdabbelt@google.com>, Arnd Bergmann <arnd@arndb.de>,
 James Bottomley <jejb@linux.ibm.com>, Hagen Paul Pfeifer <hagen@jauu.net>,
 Borislav Petkov <bp@alien8.de>, Alexander Viro <viro@zeniv.linux.org.uk>,
 Andy Lutomirski <luto@kernel.org>, Paul Walmsley <paul.walmsley@sifive.com>,
 "Kirill A. Shutemov" <kirill@shutemov.name>,
 Dan Williams <dan.j.williams@intel.com>, linux-arm-kernel@lists.infradead.org,
 linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
 linux-riscv@lists.infradead.org, Palmer Dabbelt <palmer@dabbelt.com>,
 linux-fsdevel@vger.kernel.org, Shakeel Butt <shakeelb@google.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 Rick Edgecombe <rick.p.edgecombe@intel.com>, Roman Gushchin <guro@fb.com>
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Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org

On Fri, Feb 12, 2021 at 10:18:19AM +0100, David Hildenbrand wrote:
> On 12.02.21 00:09, Mike Rapoport wrote:
> > On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote:
> > > On 11.02.21 12:27, Mike Rapoport wrote:
> > > > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote:
> > > 
> > > So let's talk about the main user-visible differences to other memfd files
> > > (especially, other purely virtual files like hugetlbfs). With secretmem:
> > > 
> > > - File content can only be read/written via memory mappings.
> > > - File content cannot be swapped out.
> > > 
> > > I think there are still valid ways to modify file content using syscalls:
> > > e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just
> > > fine.
> > These work perfectly with any file, so maybe we should have added
> > memfd_create as a flag to open(2) back then and now the secretmem file
> > descriptors?
> 
> I think open() vs memfd_create() makes sense: for open, the path specifies
> main properties (tmpfs, hugetlbfs, filesystem). On memfd, there is no such
> path and the "type" has to be specified differently.
> 
> Also, open() might open existing files - memfd always creates new files.

Yes, but still open() returns a handle to a file and memfd_create() returns
a handle to a file. The differences may be well hidden by e.g. O_MEMORY and
than features unique to memfd files will have their set of O_SOMETHING
flags.

It's the same logic that says "we already have an interface that's close
enough and it's fine to add a bunch of new flags there".
 
And here we come to the question "what are the differences that justify a
new system call?" and the answer to this is very subjective. And as such we
can continue bikeshedding forever.

-- 
Sincerely yours,
Mike.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel