From: Paolo Bonzini <pbonzini@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Yosry Ahmed <yosryahmed@google.com>,
Sean Christopherson <seanjc@google.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
michael.roth@amd.com, isaku.yamahata@intel.com,
thomas.lendacky@amd.com
Subject: Re: [PATCH 17/21] filemap: add FGP_CREAT_ONLY
Date: Wed, 28 Feb 2024 14:28:45 +0100 [thread overview]
Message-ID: <CABgObfZ9LFDrtLkMaT5LVwy0Z2QMk6SqJ104+D=w7o9i0gEu+g@mail.gmail.com> (raw)
In-Reply-To: <Zd8x3w2mwyAufKvm@casper.infradead.org>
On Wed, Feb 28, 2024 at 2:15 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Feb 27, 2024 at 06:17:34PM -0800, Yosry Ahmed wrote:
> > On Tue, Feb 27, 2024 at 6:15 PM Sean Christopherson <seanjc@google.com> wrote:
> > >
> > > On Tue, Feb 27, 2024, Paolo Bonzini wrote:
> > >
> > > This needs a changelog, and also needs to be Cc'd to someone(s) that can give it
> > > a thumbs up.
> >
> > +Matthew Wilcox
>
> If only there were an entry in MAINTAINERS for filemap.c ...
Not CCing you (or mm in general) was intentional because I first
wanted a review of the KVM APIs; of course I wouldn't have committed
it without an Acked-by. But yeah, not writing the changelog yet was
pure laziness.
Since you're here: KVM would like to add a ioctl to encrypt and
install a page into guest_memfd, in preparation for launching an
encrypted guest. For this API we want to rule out the possibility of
overwriting a page that is already in the guest_memfd's filemap,
therefore this API would pass FGP_CREAT_ONLY|FGP_CREAT
into__filemap_get_folio. Do you think this is bogus...
> This looks bogus to me, and if it's not bogus, it's incomplete.
... or if not, what incompleteness can you spot?
Thanks,
Paolo
> But it's hard to judge without a commit message that describes what it's
> supposed to mean.
>
> > >
> > > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > > > ---
> > > > include/linux/pagemap.h | 2 ++
> > > > mm/filemap.c | 4 ++++
> > > > 2 files changed, 6 insertions(+)
> > > >
> > > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> > > > index 2df35e65557d..e8ac0b32f84d 100644
> > > > --- a/include/linux/pagemap.h
> > > > +++ b/include/linux/pagemap.h
> > > > @@ -586,6 +586,7 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping,
> > > > * * %FGP_CREAT - If no folio is present then a new folio is allocated,
> > > > * added to the page cache and the VM's LRU list. The folio is
> > > > * returned locked.
> > > > + * * %FGP_CREAT_ONLY - Fail if a folio is not present
> > > > * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
> > > > * folio is already in cache. If the folio was allocated, unlock it
> > > > * before returning so the caller can do the same dance.
> > > > @@ -606,6 +607,7 @@ typedef unsigned int __bitwise fgf_t;
> > > > #define FGP_NOWAIT ((__force fgf_t)0x00000020)
> > > > #define FGP_FOR_MMAP ((__force fgf_t)0x00000040)
> > > > #define FGP_STABLE ((__force fgf_t)0x00000080)
> > > > +#define FGP_CREAT_ONLY ((__force fgf_t)0x00000100)
> > > > #define FGF_GET_ORDER(fgf) (((__force unsigned)fgf) >> 26) /* top 6 bits */
> > > >
> > > > #define FGP_WRITEBEGIN (FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE)
> > > > diff --git a/mm/filemap.c b/mm/filemap.c
> > > > index 750e779c23db..d5107bd0cd09 100644
> > > > --- a/mm/filemap.c
> > > > +++ b/mm/filemap.c
> > > > @@ -1854,6 +1854,10 @@ struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
> > > > folio = NULL;
> > > > if (!folio)
> > > > goto no_page;
> > > > + if (fgp_flags & FGP_CREAT_ONLY) {
> > > > + folio_put(folio);
> > > > + return ERR_PTR(-EEXIST);
> > > > + }
> > > >
> > > > if (fgp_flags & FGP_LOCK) {
> > > > if (fgp_flags & FGP_NOWAIT) {
> > > > --
> > > > 2.39.0
> > > >
> > > >
> > >
>
next prev parent reply other threads:[~2024-02-28 13:29 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-27 23:20 [PATCH 00/21] TDX/SNP part 1 of n, for 6.9 Paolo Bonzini
2024-02-27 23:20 ` [PATCH 01/21] KVM: x86: Split core of hypercall emulation to helper function Paolo Bonzini
2024-02-28 2:09 ` Xiaoyao Li
2024-03-05 6:24 ` Binbin Wu
2024-02-27 23:20 ` [PATCH 02/21] KVM: Allow page-sized MMU caches to be initialized with custom 64-bit values Paolo Bonzini
2024-02-29 13:46 ` Xiaoyao Li
2024-03-05 6:55 ` Binbin Wu
2024-03-26 15:56 ` Binbin Wu
2024-05-13 20:38 ` Isaku Yamahata
2024-05-13 20:51 ` Isaku Yamahata
2024-05-13 20:56 ` Sean Christopherson
2024-02-27 23:20 ` [PATCH 03/21] KVM: x86/mmu: Replace hardcoded value 0 for the initial value for SPTE Paolo Bonzini
2024-02-29 13:50 ` Xiaoyao Li
2024-03-05 7:09 ` Binbin Wu
2024-02-27 23:20 ` [PATCH 04/21] KVM: x86/mmu: Allow non-zero value for non-present SPTE and removed SPTE Paolo Bonzini
2024-02-29 7:00 ` Xu Yilun
2024-02-29 13:55 ` Xiaoyao Li
2024-03-11 23:26 ` Huang, Kai
2024-02-27 23:20 ` [PATCH 05/21] KVM: x86/mmu: Add Suppress VE bit to EPT shadow_mmio_mask/shadow_present_mask Paolo Bonzini
2024-03-01 7:26 ` Xiaoyao Li
2024-03-05 13:17 ` Binbin Wu
2024-02-27 23:20 ` [PATCH 06/21] KVM: x86/mmu: Track shadow MMIO value on a per-VM basis Paolo Bonzini
2024-03-01 7:44 ` Xiaoyao Li
2024-03-05 8:35 ` Binbin Wu
2024-03-12 1:21 ` Huang, Kai
2024-02-27 23:20 ` [PATCH 07/21] KVM: VMX: Introduce test mode related to EPT violation VE Paolo Bonzini
2024-02-28 1:56 ` Sean Christopherson
2024-03-12 1:35 ` Huang, Kai
2024-03-12 16:54 ` Sean Christopherson
2024-03-12 21:03 ` Huang, Kai
2024-02-27 23:20 ` [PATCH 08/21] KVM: VMX: Move out vmx_x86_ops to 'main.c' to dispatch VMX and TDX Paolo Bonzini
2024-02-27 23:20 ` [PATCH 09/21] KVM: VMX: Modify NMI and INTR handlers to take intr_info as function argument Paolo Bonzini
2024-03-04 8:09 ` Xiaoyao Li
2024-03-05 13:42 ` Binbin Wu
2024-03-12 1:43 ` Huang, Kai
2024-02-27 23:20 ` [PATCH 10/21] KVM: SEV: Use a VMSA physical address variable for populating VMCB Paolo Bonzini
2024-02-28 2:00 ` Sean Christopherson
2024-02-28 17:32 ` Paolo Bonzini
2024-02-29 16:02 ` Sean Christopherson
2024-02-27 23:20 ` [PATCH 11/21] KVM: x86/tdp_mmu: Init role member of struct kvm_mmu_page at allocation Paolo Bonzini
2024-03-03 4:47 ` Xu Yilun
2024-03-25 23:32 ` Edgecombe, Rick P
2024-02-27 23:20 ` [PATCH 12/21] KVM: x86/tdp_mmu: Sprinkle __must_check Paolo Bonzini
2024-03-04 8:29 ` Xiaoyao Li
2024-02-27 23:20 ` [PATCH 13/21] KVM: x86/mmu: Pass around full 64-bit error code for KVM page faults Paolo Bonzini
2024-03-04 8:56 ` Xiaoyao Li
2024-03-04 15:39 ` Sean Christopherson
2024-04-05 17:57 ` Paolo Bonzini
2024-02-27 23:20 ` [PATCH 14/21] KVM: x86/mmu: pass error code back to MMU when async pf is ready Paolo Bonzini
2024-02-28 2:03 ` Sean Christopherson
2024-02-28 13:13 ` Paolo Bonzini
2024-02-27 23:20 ` [PATCH 15/21] KVM: x86/mmu: Use PFERR_GUEST_ENC_MASK to indicate fault is private Paolo Bonzini
2024-02-27 23:20 ` [PATCH 16/21] KVM: guest_memfd: pass error up from filemap_grab_folio Paolo Bonzini
2024-03-03 14:41 ` Xu Yilun
2024-02-27 23:20 ` [PATCH 17/21] filemap: add FGP_CREAT_ONLY Paolo Bonzini
2024-02-28 2:14 ` Sean Christopherson
2024-02-28 2:17 ` Yosry Ahmed
2024-02-28 13:15 ` Matthew Wilcox
2024-02-28 13:28 ` Paolo Bonzini [this message]
2024-02-28 19:24 ` Matthew Wilcox
2024-02-28 20:17 ` Paolo Bonzini
2024-03-04 2:55 ` Xu Yilun
2024-02-27 23:20 ` [PATCH 18/21] KVM: x86: Add gmem hook for initializing memory Paolo Bonzini
2024-02-28 20:29 ` Isaku Yamahata
2024-02-27 23:20 ` [PATCH 19/21] KVM: guest_memfd: add API to undo kvm_gmem_get_uninit_pfn Paolo Bonzini
2024-03-04 4:44 ` Xu Yilun
2024-02-27 23:20 ` [PATCH 20/21] KVM: x86: Add gmem hook for invalidating memory Paolo Bonzini
2024-02-27 23:21 ` [PATCH 21/21] KVM: x86: Add gmem hook for determining max NPT mapping level Paolo Bonzini
2024-03-12 0:39 ` Binbin Wu
2024-03-12 0:48 ` Binbin Wu
2024-02-28 1:24 ` [PATCH 00/21] TDX/SNP part 1 of n, for 6.9 Sean Christopherson
2024-02-28 13:29 ` Paolo Bonzini
2024-02-28 16:39 ` Sean Christopherson
2024-02-28 17:20 ` Paolo Bonzini
2024-02-28 18:04 ` Sean Christopherson
2024-02-28 2:11 ` Sean Christopherson
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