KVM: x86/mmu: Use enable_mmio_caching to track if MMIO caching is enabled

Clear enable_mmio_caching if hardware can't support MMIO caching and use
the dedicated flag to detect if MMIO caching is enabled instead of
assuming shadow_mmio_value==0 means MMIO caching is disabled.  TDX will
use a zero value even when caching is enabled, and is_mmio_spte() isn't
so hot that it needs to avoid an extra memory access, i.e. there's no
reason to be super clever.  And the clever approach may not even be more
performant, e.g. gcc-11 lands the extra check on a non-zero value inline,
but puts the enable_mmio_caching out-of-line, i.e. avoids the few extra
uops for non-MMIO SPTEs.

Cc: Isaku Yamahata <[email protected]>
Cc: Kai Huang <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

0 files changed, 0 insertions, 0 deletions