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Wed, 04 Jun 2025 05:32:12 -0700 (PDT) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250527180245.1413463-1-tabba@google.com> <20250527180245.1413463-10-tabba@google.com> In-Reply-To: From: Fuad Tabba Date: Wed, 4 Jun 2025 13:31:36 +0100 X-Gm-Features: AX0GCFtQkOaG8vC3W7Pt65KUSQEh4Kx0R_oAJds8qIizcawQAXuvpXqZaNOzgzg Message-ID: Subject: Re: [PATCH v10 09/16] KVM: guest_memfd: Track shared memory support in memslot To: David Hildenbrand Cc: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com Content-Type: text/plain; charset="UTF-8" On Wed, 4 Jun 2025 at 13:25, David Hildenbrand wrote: > > On 27.05.25 20:02, Fuad Tabba wrote: > > Track whether a guest_memfd-backed memslot supports shared memory within > > the memslot itself, using the flags field. The top half of memslot flags > > is reserved for internal use in KVM. Add a flag there to track shared > > memory support. > > > > This saves the caller from having to check the guest_memfd-backed file > > for this support, a potentially more expensive operation due to the need > > to get/put the file. > > > > Suggested-by: David Hildenbrand > > Signed-off-by: Fuad Tabba > > --- > > include/linux/kvm_host.h | 11 ++++++++++- > > virt/kvm/guest_memfd.c | 8 ++++++-- > > 2 files changed, 16 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index ba83547e62b0..edb3795a64b9 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -54,7 +54,8 @@ > > * used in kvm, other bits are visible for userspace which are defined in > > * include/uapi/linux/kvm.h. > > */ > > -#define KVM_MEMSLOT_INVALID (1UL << 16) > > +#define KVM_MEMSLOT_INVALID (1UL << 16) > > +#define KVM_MEMSLOT_SUPPORTS_SHARED (1UL << 17) > > Should there be a "GMEM" in there? I'll change it to KVM_MEMSLOT_SUPPORTS_GMEM_SHARED. I thought of adding _MEM as well, but it starts getting too long :) Thanks, /fuad > -- > Cheers, > > David / dhildenb >