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From: Kai Huang <kai.huang@intel.com>
To: kvm@vger.kernel.org
Cc: pbonzini@redhat.com, bgardon@google.com, seanjc@google.com,
	vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com,
	joro@8bytes.org, Kai Huang <kai.huang@intel.com>
Subject: [PATCH v2 2/3] KVM: x86/mmu: Fix pf_fixed count in tdp_mmu_map_handle_target_level()
Date: Fri,  7 May 2021 11:34:01 +1200	[thread overview]
Message-ID: <76406bd7aad0cec458e832639c7a2de963e70990.1620343751.git.kai.huang@intel.com> (raw)
In-Reply-To: <cover.1620343751.git.kai.huang@intel.com>

Currently pf_fixed is not increased when prefault is true.  This is not
correct, since prefault here really means "async page fault completed".
In that case, the original page fault from the guest was morphed into as
async page fault and pf_fixed was not increased.  So when prefault
indicates async page fault is completed, pf_fixed should be increased.

Additionally, currently pf_fixed is also increased even when page fault
is spurious, while legacy MMU increases pf_fixed when page fault returns

To fix above two issues, change to increase pf_fixed when return value
is not RET_PF_SPURIOUS (RET_PF_RETRY has already been ruled out by
reaching here).

More information:

Fixes: bb18842e2111 ("kvm: x86/mmu: Add TDP MMU PF handler")
Signed-off-by: Kai Huang <kai.huang@intel.com>
 arch/x86/kvm/mmu/tdp_mmu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index ed85b09f0119..c389d20418e3 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -942,7 +942,11 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, int write,
-	if (!prefault)
+	/*
+	 * Increase pf_fixed in both RET_PF_EMULATE and RET_PF_FIXED to be
+	 * consistent with legacy MMU behavior.
+	 */
+	if (ret != RET_PF_SPURIOUS)
 	return ret;

  parent reply	other threads:[~2021-05-06 23:34 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-06 23:33 [PATCH v2 0/3] TDP MMU: several minor fixes or improvements Kai Huang
2021-05-06 23:34 ` [PATCH v2 1/3] KVM: x86/mmu: Fix return value in tdp_mmu_map_handle_target_level() Kai Huang
2021-05-06 23:34 ` Kai Huang [this message]
2021-05-07 17:23   ` [PATCH v2 2/3] KVM: x86/mmu: Fix pf_fixed count " Sean Christopherson
2021-05-06 23:34 ` [PATCH v2 3/3] KVM: x86/mmu: Fix TDP MMU page table level Kai Huang
2021-05-06 23:46   ` Kai Huang
2021-05-27  2:03 ` [PATCH v2 0/3] TDP MMU: several minor fixes or improvements Kai Huang

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