Improve HFENCE.GVMA commentary

See #793

1 files changed, 7 insertions, 6 deletions

diff --git a/src/hypervisor.tex b/src/hypervisor.tex
index b8c1994..13cb599 100644
--- a/src/hypervisor.tex
+++ b/src/hypervisor.tex
@@ -2009,12 +2009,13 @@ the latter cache that match the HFENCE.GVMA's address and VMID arguments.
 More commonly, implementations contain address-translation caches that map
 guest virtual addresses directly to supervisor physical addresses, removing
 a level of indirection.
-For such implementations, any entry that was populated using a G-stage
-translation that is ordered by an HFENCE.GVMA instruction must be flushed.
-Because it is often impractical to determine which such entries match the
-HFENCE.GVMA's address argument, a common technique is to flush all entries
-that match the HFENCE.GVMA's VMID argument, regardless of the address
-argument.
+For such implementations, any entry whose guest virtual address maps to
+a guest physical address that matches the HFENCE.GVMA's address and VMID
+arguments must be flushed.
+Selectively flushing entries in this fashion requires tagging them with
+the guest physical address, which is costly, and so a common technique is
+to flush all entries that match the HFENCE.GVMA's VMID argument, regardless
+of the address argument.
 \end{commentary}
 
 \begin{commentary}