On Wed, Jan 04, 2023 at 08:42:56PM -0600, Michael Roth wrote:
> Obviously I need to add some proper documentation for this, but a 1
> return basically means 'private_fault' pass-by-ref arg has been set
> with the appropriate value, whereas 0 means "there's no platform-specific
> handling for this, so if you have some generic way to determine this
> then use that instead".
Still binary, tho, and can be bool, right?
I.e., you can just as well do:
if (static_call(kvm_x86_fault_is_private)(kvm, gpa, err, &private_fault))
goto out;
at the call site.
> This is mainly to handle CONFIG_HAVE_KVM_PRIVATE_MEM_TESTING, which
> just parrots whatever kvm_mem_is_private() returns to support running
> KVM selftests without needed hardware/platform support. If we don't
> take care to skip this check where the above fault_is_private() hook
> returns 1, then it ends up breaking SNP in cases where the kernel has
> been compiled with CONFIG_HAVE_KVM_PRIVATE_MEM_TESTING, since SNP
> relies on the page fault flags to make this determination, not
> kvm_mem_is_private(), which normally only tracks the memory attributes
> set by userspace via KVM_SET_MEMORY_ATTRIBUTES ioctl.
Some of that explanation belongs into the commit message, which is a bit
lacking...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
