vmm: linux: Do not use guest_memfd outside of TEE builds (fixes #478) #479
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…iners#478) aarch64 KVM has recently introduced guest_memfd support, but since there are no VM TEEs with upstream support on that arch, it returns EINVAL when we try to create a non-mappable memfd (which is what flags==0 implies). Then.. even if we make it mappable and skip setting the private flag, we get a 100% CPU busy loop in the guest. Same happens in QEMU though so that's not a libkrun bug. Still, let's avoid *all* of that by not trying to use guest_memfd for protecting the VM's memory outside of platforms where that's explicitly supported (SEV/TDX). Signed-off-by: Val Packett <val@invisiblethingslab.com>
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tylerfanelli
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tylerfanelli
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Dec 1, 2025
| .map_err(Error::SetUserMemoryRegion)?; | ||
| }; | ||
| } else { | ||
| if !self.fd.check_extension(GuestMemfd) { |
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Can this be made an else if to avoid unnecessary nesting?
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If this was made into an else if, we would need another conditional branch to return Error::KvmCap(GuestMemfd). It's better as it is here.
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aarch64 KVM has recently introduced guest_memfd support, but since there are no VM TEEs with upstream support on that arch, it returns EINVAL when we try to create a non-mappable memfd (which is what flags==0 implies).
Then.. even if we make it mappable and skip setting the private flag, we get a 100% CPU busy loop in the guest. Same happens in QEMU though so that's not a libkrun bug. Still, let's avoid all of that by not trying to use guest_memfd for protecting the VM's memory outside of platforms where that's explicitly supported (SEV/TDX).