linux-kernel - [PATCH 2/5] KVM: e500: use shadow TLB entry as witness for writability

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Message-ID: <20250109133817.314401-3-pbonzini@redhat.com>
Date: Thu,  9 Jan 2025 14:38:14 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: oliver.upton@...ux.dev,
	Will Deacon <will@...nel.org>,
	Anup Patel <apatel@...tanamicro.com>,
	Andrew Jones <ajones@...tanamicro.com>,
	seanjc@...gle.com,
	linuxppc-dev@...ts.ozlabs.org,
	regressions@...ts.linux.dev
Subject: [PATCH 2/5] KVM: e500: use shadow TLB entry as witness for writability

kvmppc_e500_ref_setup is returning whether the guest TLB entry is writable,
which is than passed to kvm_release_faultin_page.  This makes little sense
for two reasons: first, because the function sets up the private data for
the page and the return value feels like it has been bolted on the side;
second, because what really matters is whether the _shadow_ TLB entry is
writable.  If it is not writable, the page can be released as non-dirty.
Shift from using tlbe_is_writable(gtlbe) to doing the same check on
the shadow TLB entry.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/powerpc/kvm/e500_mmu_host.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index 732335444d68..06e23c625be0 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -242,7 +242,7 @@ static inline int tlbe_is_writable(struct kvm_book3e_206_tlb_entry *tlbe)
 	return tlbe->mas7_3 & (MAS3_SW|MAS3_UW);
 }
 
-static inline bool kvmppc_e500_ref_setup(struct tlbe_ref *ref,
+static inline void kvmppc_e500_ref_setup(struct tlbe_ref *ref,
 					 struct kvm_book3e_206_tlb_entry *gtlbe,
 					 kvm_pfn_t pfn, unsigned int wimg)
 {
@@ -251,8 +251,6 @@ static inline bool kvmppc_e500_ref_setup(struct tlbe_ref *ref,
 
 	/* Use guest supplied MAS2_G and MAS2_E */
 	ref->flags |= (gtlbe->mas2 & MAS2_ATTRIB_MASK) | wimg;
-
-	return tlbe_is_writable(gtlbe);
 }
 
 static inline void kvmppc_e500_ref_release(struct tlbe_ref *ref)
@@ -493,10 +491,11 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
 			goto out;
 		}
 	}
-	writable = kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg);
 
+	kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg);
 	kvmppc_e500_setup_stlbe(&vcpu_e500->vcpu, gtlbe, tsize,
 				ref, gvaddr, stlbe);
+	writable = tlbe_is_writable(stlbe);
 
 	/* Clear i-cache for new pages */
 	kvmppc_mmu_flush_icache(pfn);
-- 
2.47.1