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AJvYcCVApDeCUo0LaQIcQkSM0EMgvgI3Ci9xsG54G+1vD0kk4+VCt8YlJUIafjBw2nFWyIMkx3kXP1J1tg==@kvack.org X-Gm-Message-State: AOJu0YxUl+9E7viOsFRti84rUINkapxMjqfqI5291Tmyq+tdcnZKuhqe 2bcHPV3N8S26rnjSkCNHWqG96Hs8MiN6OWRzCQ0bcJL3L/B/8WOuq7P/tAi78J/d1tFCW2C5Uwg QLHja9JIVnf96yIAREvyzLIC/BZ37aYLq8+ib1j1T X-Gm-Gg: ASbGnctuRTWASjNcV1QUtx9/QftzttucxTMznwLbkD6Hj4c0ONAJCQDxtWX2kk8Pr3h t90i/4AgsQ9CACGKdVYo11gicB0QpOQ1KmyzA4GaJTnNPzp0hR3zwujqqY3b0d9yCJ2GBrd1GxA 6WPcZK4oec0XcOHzn1BmKH3LCBczNvZC6YTLLEMbsm/BiXWqQjFjGAd7VBGdXHKR+vNf20ViRMj kuZWpQEKQ1bi9+d4GIoQd0WmSt72/I3U9wFRvA= X-Google-Smtp-Source: AGHT+IFmDnj7+7K2+mnfOTNdR+Aw+YaytnwDDjpn3qAQ9yqrximLoYRf4l3rk/6s3TFG9z/SXMskhFKqUBehgiK3Wys= X-Received: by 2002:a17:902:e84a:b0:234:c37:85a with SMTP id d9443c01a7336-23e1ab85c7amr2901485ad.24.1752585621695; Tue, 15 Jul 2025 06:20:21 -0700 (PDT) MIME-Version: 1.0 References: <20250613005400.3694904-1-michael.roth@amd.com> <20250613005400.3694904-4-michael.roth@amd.com> In-Reply-To: <20250613005400.3694904-4-michael.roth@amd.com> From: Vishal Annapurve Date: Tue, 15 Jul 2025 06:20:09 -0700 X-Gm-Features: Ac12FXw0-WaLjY8qLo4gIdV3Uj1d2qvRKcayg-mqAaNlcSi7aOXIlvsa9VQBB5w Message-ID: Subject: Re: [PATCH RFC v1 3/5] KVM: guest_memfd: Call arch invalidation hooks when converting to shared To: Michael Roth Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@redhat.com, tabba@google.com, ackerleytng@google.com, ira.weiny@intel.com, thomas.lendacky@amd.com, pbonzini@redhat.com, seanjc@google.com, vbabka@suse.cz, joro@8bytes.org, pratikrajesh.sampat@amd.com, liam.merwick@oracle.com, yan.y.zhao@intel.com, aik@amd.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: n4migyp4wnaeauu3igzgifns3un58nu7 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 75B9C80002 X-Rspam-User: X-HE-Tag: 1752585623-759047 X-HE-Meta: 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 j+Zu07gd kqP+b+CuDo6HRixTFfuZX1tCZSs348RS+MRg/sOS3FQaAOPys2/aVTzcW2PUHQvux4bi9fXoseo54QRB8O6MucapLjULPmXSLLisP2HHou8XpS1XUVtdKEIt7UgD+KmFxEUtn0CWhMdHjuyQzgSMm3IdkyyOMexz2jNlAf4ho0wBG6SS+U8Lf9FLEPv8SRENC5IEP8phthAHrlwAbXCt6pevfgBUryXaFL7B+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 12, 2025 at 5:56=E2=80=AFPM Michael Roth = wrote: > > When guest_memfd is used for both shared/private memory, converting > pages to shared may require kvm_arch_gmem_invalidate() to be issued to > return the pages to an architecturally-defined "shared" state if the > pages were previously allocated and transitioned to a private state via > kvm_arch_gmem_prepare(). > > Handle this by issuing the appropriate kvm_arch_gmem_invalidate() calls > when converting ranges in the filemap to a shared state. > > Signed-off-by: Michael Roth > --- > virt/kvm/guest_memfd.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index b77cdccd340e..f27e1f3962bb 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -203,6 +203,28 @@ static int kvm_gmem_shareability_apply(struct inode = *inode, > struct maple_tree *mt; > > mt =3D &kvm_gmem_private(inode)->shareability; > + > + /* > + * If a folio has been allocated then it was possibly in a privat= e > + * state prior to conversion. Ensure arch invalidations are issue= d > + * to return the folio to a normal/shared state as defined by the > + * architecture before tracking it as shared in gmem. > + */ > + if (m =3D=3D SHAREABILITY_ALL) { > + pgoff_t idx; > + > + for (idx =3D work->start; idx < work->start + work->nr_pa= ges; idx++) { It is redundant to enter this loop for VM variants that don't need this loop e.g. for pKVM/TDX. I think KVM can dictate a set of rules (based on VM type) that guest_memfd will follow for memory management when it's created, e.g. something like: 1) needs pfn invalidation 2) needs zeroing on shared faults 3) needs zeroing on allocation > + struct folio *folio =3D filemap_lock_folio(inode-= >i_mapping, idx); > + > + if (!IS_ERR(folio)) { > + kvm_arch_gmem_invalidate(folio_pfn(folio)= , > + folio_pfn(folio)= + folio_nr_pages(folio)); > + folio_unlock(folio); > + folio_put(folio); > + } > + } > + } > + > return kvm_gmem_shareability_store(mt, work->start, work->nr_page= s, m); > } > > -- > 2.25.1 >