[RFC PATCH v1 10/37] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs
STALE242d
From: Ackerley Tng <hidden>
Date: 2025-10-17 20:12:46
Also in:
cgroups, kvm, linux-doc, linux-fsdevel, linux-kselftest, linux-mm, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Sean Christopherson <seanjc@google.com> Now that guest_memfd supports tracking private vs. shared within gmem itself, allow userspace to specify INIT_SHARED on a guest_memfd instance for x86 Confidential Computing (CoCo) VMs, so long as per-VM attributes are disabled, i.e. when it's actually possible for a guest_memfd instance to contain shared memory. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/x86.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5e38c4c9cf63c..4ad451982380e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c@@ -13941,14 +13941,13 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) } #ifdef CONFIG_KVM_GUEST_MEMFD -/* - * KVM doesn't yet support initializing guest_memfd memory as shared for VMs - * with private memory (the private vs. shared tracking needs to be moved into - * guest_memfd). - */ bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm) { - return !kvm_arch_has_private_mem(kvm); + /* + * INIT_SHARED isn't supported if the memory attributes are per-VM, + * in which case guest_memfd can _only_ be used for private memory. + */ + return !vm_memory_attributes || !kvm_arch_has_private_mem(kvm); } #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE
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2.51.0.858.gf9c4a03a3a-goog