On Thu, Apr 25, 2024, Xiaoyao Li wrote:
> On 4/24/2024 12:53 AM, Sean Christopherson wrote:
> > Fix a goof where KVM fails to re-initialize the set of supported VM types,
> > resulting in KVM overreporting the set of supported types when a vendor
> > module is reloaded with incompatible settings. E.g. unload kvm-intel.ko,
> > reload with ept=0, and KVM will incorrectly treat SW_PROTECTED_VM as
> > supported.
>
> Hah, this reminds me of the bug of msrs_to_save[] and etc.
>
> 7a5ee6edb42e ("KVM: X86: Fix initialization of MSR lists")
Yeah, and we had the same bug with allow_smaller_maxphyaddr
88213da23514 ("kvm: x86: disable the narrow guest module parameter on unload")
If the side effects of linking kvm.ko into kvm-{amd,intel}.ko weren't so painful
for userspace, I would more seriously consider pursuing that in advance of
multi-KVM[*]. Because having KVM be fully self-contained has some *really* nice
properties, e.g. eliminates this entire class of bugs, eliminates a huge pile of
exports, etc.
: > Since the symbols in the new module are invisible outside, I recommend:
: > new kvm_intel.ko = kvm_intel.ko + kvm.ko
: > new kvm_amd.ko = kvm_amd.ko + kvm.ko
:
: Yeah, Paolo also suggested this at LPC.
[*] https://lore.kernel.org/all/ZWYtDGH5p4RpGYBw@xxxxxxxxxx
