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bh=ZFnNkL3gAOH3Set42pPIr6QBedDLQIpiu7ddBCaA7LI=; b=gYKuUYiuLAos2CQzp6ejIIOtGkrfYo3RhmFnHSoPseXDJb6TblDHNXT4W15uugK02icL0p +tHh9+E2sq99QSAw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 826BB3EA63; Tue, 16 Dec 2025 13:53:07 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id YNAfD0NkQWnjKQAAD6G6ig (envelope-from ); Tue, 16 Dec 2025 13:53:07 +0000 From: Fabiano Rosas To: Peter Xu , qemu-devel@nongnu.org Cc: Juraj Marcin , David Hildenbrand , Paolo Bonzini , Chenyi Qiang , peterx@redhat.com, Alexey Kardashevskiy , Li Xiaoyao Subject: Re: [PATCH v3 01/12] kvm: Decouple memory attribute check from kvm_guest_memfd_supported In-Reply-To: <20251215205203.1185099-2-peterx@redhat.com> References: <20251215205203.1185099-1-peterx@redhat.com> <20251215205203.1185099-2-peterx@redhat.com> Date: Tue, 16 Dec 2025 10:53:04 -0300 Message-ID: <87345a354v.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 153195BCD6 X-Spamd-Result: default: False [-5.51 / 50.00]; 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envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Xu writes: > From: Xiaoyao Li > > With the mmap support of guest memfd, KVM allows usersapce to create > guest memfd serving as normal non-private memory for X86 DEFEAULT VM. > However, KVM doesn't support private memory attriute for X86 DEFAULT > VM. > > Make kvm_guest_memfd_supported not rely on KVM_MEMORY_ATTRIBUTE_PRIVATE > and check KVM_MEMORY_ATTRIBUTE_PRIVATE separately when the machine > requires guest_memfd to serve as private memory. > > This allows QMEU to create guest memfd with mmap to serve as the memory > backend for X86 DEFAULT VM. > > Signed-off-by: Xiaoyao Li > Signed-off-by: Peter Xu > --- > include/system/kvm.h | 1 + > accel/kvm/kvm-all.c | 8 ++++++-- > accel/stubs/kvm-stub.c | 5 +++++ > system/physmem.c | 8 ++++++++ > 4 files changed, 20 insertions(+), 2 deletions(-) > > diff --git a/include/system/kvm.h b/include/system/kvm.h > index 8f9eecf044..b5811c90f1 100644 > --- a/include/system/kvm.h > +++ b/include/system/kvm.h > @@ -561,6 +561,7 @@ int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp); > > int kvm_set_memory_attributes_private(hwaddr start, uint64_t size); > int kvm_set_memory_attributes_shared(hwaddr start, uint64_t size); > +bool kvm_private_memory_attribute_supported(void); > > int kvm_convert_memory(hwaddr start, hwaddr size, bool to_private); > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index 28006d73c5..59836ebdff 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -1501,6 +1501,11 @@ int kvm_set_memory_attributes_shared(hwaddr start, uint64_t size) > return kvm_set_memory_attributes(start, size, 0); > } > > +bool kvm_private_memory_attribute_supported(void) > +{ > + return !!(kvm_supported_memory_attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE); > +} > + > /* Called with KVMMemoryListener.slots_lock held */ > static void kvm_set_phys_mem(KVMMemoryListener *kml, > MemoryRegionSection *section, bool add) > @@ -2781,8 +2786,7 @@ static int kvm_init(AccelState *as, MachineState *ms) > kvm_supported_memory_attributes = kvm_vm_check_extension(s, KVM_CAP_MEMORY_ATTRIBUTES); > kvm_guest_memfd_supported = > kvm_vm_check_extension(s, KVM_CAP_GUEST_MEMFD) && > - kvm_vm_check_extension(s, KVM_CAP_USER_MEMORY2) && > - (kvm_supported_memory_attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE); > + kvm_vm_check_extension(s, KVM_CAP_USER_MEMORY2); > kvm_pre_fault_memory_supported = kvm_vm_check_extension(s, KVM_CAP_PRE_FAULT_MEMORY); > > if (s->kernel_irqchip_split == ON_OFF_AUTO_AUTO) { > diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c > index 68cd33ba97..73f04eb589 100644 > --- a/accel/stubs/kvm-stub.c > +++ b/accel/stubs/kvm-stub.c > @@ -125,3 +125,8 @@ int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp) > { > return -ENOSYS; > } > + > +bool kvm_private_memory_attribute_supported(void) > +{ > + return false; > +} > diff --git a/system/physmem.c b/system/physmem.c > index c9869e4049..3555d2f6f7 100644 > --- a/system/physmem.c > +++ b/system/physmem.c > @@ -2211,6 +2211,14 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) > object_get_typename(OBJECT(current_machine->cgs))); > goto out_free; > } > + > + if (!kvm_private_memory_attribute_supported()) { > + error_setg(errp, "cannot set up private guest memory for %s: " > + " KVM does not support private memory attribute", > + object_get_typename(OBJECT(current_machine->cgs))); > + goto out_free; > + } Hm, it took me a while to understand why this is under (new_block->flags & RAM_GUEST_MEMFD) but checking for private memory support. If it's at all feasible I would just squash all those patches doing s/guest_memfd/guest_memfd_private/ to avoid having intermediate patches where the terminology is not aligned. Anyway, up to you. For this one: Reviewed-by: Fabiano Rosas