Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.32 as permitted sender) client-ip=23.128.96.32;
Date:   Mon, 9 Oct 2023 13:20:06 -0700
In-Reply-To: <20231009200608.GJ800259@ZenIV>
Mime-Version: 1.0
References: <20230928180651.1525674-1-pbonzini@redhat.com> <169595365500.1386813.6579237770749312873.b4-ty@google.com>
 <20231009022248.GD800259@ZenIV> <ZSQO4fHaAxDkbGyz@google.com> <20231009200608.GJ800259@ZenIV>
Message-ID: <ZSRgdgQe3fseEQpf@google.com>
Subject: Re: [PATCH gmem FIXUP] kvm: guestmem: do not use a file system
From:   Sean Christopherson <seanjc@google.com>
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Paolo Bonzini <pbonzini@redhat.com>
Content-Type: text/plain; charset="us-ascii"
Precedence: bulk

On Mon, Oct 09, 2023, Al Viro wrote:
> On Mon, Oct 09, 2023 at 07:32:48AM -0700, Sean Christopherson wrote:
> 
> > Yeah, we found that out the hard way.  Is using the "secure" variant to get a
> > per-file inode a sane approach, or is that abuse that's going to bite us too?
> > 
> > 	/*
> > 	 * Use the so called "secure" variant, which creates a unique inode
> > 	 * instead of reusing a single inode.  Each guest_memfd instance needs
> > 	 * its own inode to track the size, flags, etc.
> > 	 */
> > 	file = anon_inode_getfile_secure(anon_name, &kvm_gmem_fops, gmem,
> > 					 O_RDWR, NULL);
> 
> Umm...  Is there any chance that your call site will ever be in a module?
> If not, you are probably OK with that variant.

Yes, this code can be compiled as a module.  I assume there issues with the inode
outliving the module?