linux-kernel - [PATCH 3/5] KVM: e500: track host-writability of pages

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Message-ID: <20250109133817.314401-4-pbonzini@redhat.com>
Date: Thu,  9 Jan 2025 14:38:15 +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 3/5] KVM: e500: track host-writability of pages

Add the possibility of marking a page so that the UW and SW bits are
force-cleared.  This is stored in the private info so that it persists
across multiple calls to kvmppc_e500_setup_stlbe.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/powerpc/kvm/e500.h          |  2 ++
 arch/powerpc/kvm/e500_mmu_host.c | 15 +++++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kvm/e500.h b/arch/powerpc/kvm/e500.h
index 6d0d329cbb35..f9acf866c709 100644
--- a/arch/powerpc/kvm/e500.h
+++ b/arch/powerpc/kvm/e500.h
@@ -34,6 +34,8 @@ enum vcpu_ftr {
 #define E500_TLB_BITMAP		(1 << 30)
 /* TLB1 entry is mapped by host TLB0 */
 #define E500_TLB_TLB0		(1 << 29)
+/* entry is writable on the host */
+#define E500_TLB_WRITABLE	(1 << 28)
 /* bits [6-5] MAS2_X1 and MAS2_X0 and [4-0] bits for WIMGE */
 #define E500_TLB_MAS2_ATTR	(0x7f)
 
diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index 06e23c625be0..e332a10fff00 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -45,11 +45,14 @@ static inline unsigned int tlb1_max_shadow_size(void)
 	return host_tlb_params[1].entries - tlbcam_index - 1;
 }
 
-static inline u32 e500_shadow_mas3_attrib(u32 mas3, int usermode)
+static inline u32 e500_shadow_mas3_attrib(u32 mas3, bool writable, int usermode)
 {
 	/* Mask off reserved bits. */
 	mas3 &= MAS3_ATTRIB_MASK;
 
+	if (!writable)
+		mas3 &= ~(MAS3_UW|MAS3_SW);
+
 #ifndef CONFIG_KVM_BOOKE_HV
 	if (!usermode) {
 		/* Guest is in supervisor mode,
@@ -244,10 +247,13 @@ static inline int tlbe_is_writable(struct kvm_book3e_206_tlb_entry *tlbe)
 
 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)
+					 kvm_pfn_t pfn, unsigned int wimg,
+					 bool writable)
 {
 	ref->pfn = pfn;
 	ref->flags = E500_TLB_VALID;
+	if (writable)
+		ref->flags |= E500_TLB_WRITABLE;
 
 	/* Use guest supplied MAS2_G and MAS2_E */
 	ref->flags |= (gtlbe->mas2 & MAS2_ATTRIB_MASK) | wimg;
@@ -303,6 +309,7 @@ static void kvmppc_e500_setup_stlbe(
 {
 	kvm_pfn_t pfn = ref->pfn;
 	u32 pr = vcpu->arch.shared->msr & MSR_PR;
+	bool writable = !!(ref->flags & E500_TLB_WRITABLE);
 
 	BUG_ON(!(ref->flags & E500_TLB_VALID));
 
@@ -310,7 +317,7 @@ static void kvmppc_e500_setup_stlbe(
 	stlbe->mas1 = MAS1_TSIZE(tsize) | get_tlb_sts(gtlbe) | MAS1_VALID;
 	stlbe->mas2 = (gvaddr & MAS2_EPN) | (ref->flags & E500_TLB_MAS2_ATTR);
 	stlbe->mas7_3 = ((u64)pfn << PAGE_SHIFT) |
-			e500_shadow_mas3_attrib(gtlbe->mas7_3, pr);
+			e500_shadow_mas3_attrib(gtlbe->mas7_3, writable, pr);
 }
 
 static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
@@ -492,7 +499,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
 		}
 	}
 
-	kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg);
+	kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg, true);
 	kvmppc_e500_setup_stlbe(&vcpu_e500->vcpu, gtlbe, tsize,
 				ref, gvaddr, stlbe);
 	writable = tlbe_is_writable(stlbe);
-- 
2.47.1