linux-kernel - [PATCH v2 2/7] KVM: x86: Invoke kvm_mmu_unload() directly on CR4.PCIDE change

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Message-Id: <20220225182248.3812651-3-seanjc@google.com>
Date:   Fri, 25 Feb 2022 18:22:43 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: [PATCH v2 2/7] KVM: x86: Invoke kvm_mmu_unload() directly on
 CR4.PCIDE change

Replace a KVM_REQ_MMU_RELOAD request with a direct kvm_mmu_unload() call
when the guest's CR4.PCIDE changes.  This will allow tweaking the logic
of KVM_REQ_MMU_RELOAD to free only obsolete/invalid roots, which is the
historical intent of KVM_REQ_MMU_RELOAD.  The recent PCIDE behavior is
the only user of KVM_REQ_MMU_RELOAD that doesn't mark affected roots as
obsolete, needs to unconditionally unload the entire MMU, _and_ affects
only the current vCPU.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2157284d05b0..579b26ffc124 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1077,7 +1077,7 @@ void kvm_post_set_cr4(struct kvm_vcpu *vcpu, unsigned long old_cr4, unsigned lon
 	 */
 	if (!tdp_enabled &&
 	    (cr4 & X86_CR4_PCIDE) && !(old_cr4 & X86_CR4_PCIDE))
-		kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
+		kvm_mmu_unload(vcpu);
 
 	/*
 	 * The TLB has to be flushed for all PCIDs if any of the following
-- 
2.35.1.574.g5d30c73bfb-goog