linux-kernel - [PATCH 3/3] KVM: x86: Clean up documentation for KVM_X86_QUIRK_SLOT_ZAP

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Message-ID: <20241009192345.1148353-4-seanjc@google.com>
Date: Wed,  9 Oct 2024 12:23:45 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Yan Zhao <yan.y.zhao@...el.com>
Subject: [PATCH 3/3] KVM: x86: Clean up documentation for KVM_X86_QUIRK_SLOT_ZAP_ALL

Massage the documentation for KVM_X86_QUIRK_SLOT_ZAP_ALL to call out that
it applies to moved memslots as well as deleted memslots, to avoid KVM's
"fast zap" terminology (which has no meaning for userspace), and to reword
the documented targeted zap behavior to specifically say that KVM _may_
zap a subset of all SPTEs.  As evidenced by the fix to zap non-leafs SPTEs
with gPTEs, formally documenting KVM's exact internal behavior is risky
and unnecessary.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 Documentation/virt/kvm/api.rst | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index e32471977d0a..edc070c6e19b 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8098,13 +8098,15 @@ KVM_X86_QUIRK_MWAIT_NEVER_UD_FAULTS By default, KVM emulates MONITOR/MWAIT (if
                                     KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT is
                                     disabled.
 
-KVM_X86_QUIRK_SLOT_ZAP_ALL          By default, KVM invalidates all SPTEs in
-                                    fast way for memslot deletion when VM type
-                                    is KVM_X86_DEFAULT_VM.
-                                    When this quirk is disabled or when VM type
-                                    is other than KVM_X86_DEFAULT_VM, KVM zaps
-                                    only leaf SPTEs that are within the range of
-                                    the memslot being deleted.
+KVM_X86_QUIRK_SLOT_ZAP_ALL          By default, for KVM_X86_DEFAULT_VM VMs, KVM
+                                    invalidates all SPTEs in all memslots and
+                                    address spaces when a memslot is deleted or
+                                    moved.  When this quirk is disabled (or the
+                                    VM type isn't KVM_X86_DEFAULT_VM), KVM only
+                                    ensures the backing memory of the deleted
+                                    or moved memslot isn't reachable, i.e KVM
+                                    _may_ invalidate only SPTEs related to the
+                                    memslot.
 =================================== ============================================
 
 7.32 KVM_CAP_MAX_VCPU_ID
-- 
2.47.0.rc1.288.g06298d1525-goog