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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: k4rtzcutua9fa4kw7dw1qm9rz1iienh7 X-Rspamd-Queue-Id: AC6F314000F X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1720679196-715179 X-HE-Meta: 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 1vcIksML YF3npbhzGK4hwtGYkj+sNzGH6SMke7Hkc/GRCkLaFO7mA6bYUgwxPPywVpVr7SQ4P8VRR8DmQJuU5r+GEn39okNvn3BSKWQNnlUkKqvZ1dZQKj3X2dSpkU1DPk8S6ex0HknoW4ykmjuXZXwk0A8Eh5xaIHoc/k1+ZR/r7fwMkyQeVQedpyVteJiz1LPEI9aZnVckvnQhK7bremS48CykbnpaVtNqi+AWdyA0784NFKzAB/60K0BeuULF+yajltYAMybqHhsdvCnwBNpVafzsvmuLLfHStfuakkZMPzPZ/jWXPqzbOozWHkOyuRrRtAgse6ZQ3KUGGyXKcOaEu4UllV2xbR+lCsJKIi/Q4hUOIbRAj3uxsF+RvNjzPJuR77zC7jOquLYMfVb0VtETTiXxACLLeBuWbKZ2GLIWAMVFezWYAgECwHNfmACRmzFfSNqvQbB0TsD62HDQUH6eDus9ctLjblg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000767, 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 7/9/24 15:20, Patrick Roy wrote: > If KVM_GMEM_NO_DIRECT_MAP is set, and KVM tries to internally access > guest-private memory inside kvm_{read,write}_guest, or via a > gfn_to_pfn_cache, temporarily restore the direct map entry. > > To avoid race conditions between two threads restoring or zapping direct > map entries for the same page and potentially interfering with each > other (e.g. unfortune interweavings of map->read->unmap in the form of > map(A)->map(B)->read(A)->unmap(A)->read(B) [BOOM]), the following > invariant is upheld in this patch: > > - Only a single gfn_to_pfn_cache can exist for any given pfn, and I think this is not ensured. You can however use set_page_private()/page_private() to count the number of references. Paolo > - All non-gfn_to_pfn_cache code paths that temporarily restore direct > map entries complete the entire map->access->unmap critical section > while holding the folio lock.