On 1/26/22 17:22, Sean Christopherson wrote:
I don't like preceeding, because that will likely lead to a crash and/or WARNs if
KVM call the helper at the right time but with the wrong VMCS loaded, i.e. if
vmcs01.shadow_vmcs is left NULL, as many paths assumes vmcs01 is allocated if they
are reached with VMCS shadowing enabled. At the very least, it will leak memory
because vmcs02.shadow_vmcs is never freed.
Maybe this to try and clarify things? Compile tested only...
Your patch is okay, just with an extra paragraph in the commit message:
The previous code WARNed but continued anyway with the allocation,
presumably in an attempt to avoid NULL pointer dereference.
However, alloc_vmcs (and hence alloc_shadow_vmcs) can fail, and
indeed the sole caller does:
if (enable_shadow_vmcs && !alloc_shadow_vmcs(vcpu))
goto out_shadow_vmcs;
which makes it not a useful attempt.
Paolo
