Subject: [PATCH v4 02/46] KVM: PPC: Book3S HV: Add a function to filter guest LPCR bits

From: Nicholas Piggin <[email-masked]>
Date: Tue, 23 Mar 2021 11:02:21 +1000

Guest LPCR depends on hardware type, and future changes will add
restrictions based on errata and guest MMU mode. Move this logic
to a common function and use it for the cases where the guest
wants to update its LPCR (or the LPCR of a nested guest).

Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/include/asm/kvm_book3s.h |  2 +
 arch/powerpc/kvm/book3s_hv.c          | 60 ++++++++++++++++++---------
 arch/powerpc/kvm/book3s_hv_nested.c   |  3 +-
 3 files changed, 45 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index 2f5f919f6cd3..3eec3ef6f083 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -258,6 +258,8 @@ extern long kvmppc_hv_get_dirty_log_hpt(struct kvm *kvm,
 extern void kvmppc_harvest_vpa_dirty(struct kvmppc_vpa *vpa,
 			struct kvm_memory_slot *memslot,
 			unsigned long *map);
+extern unsigned long kvmppc_filter_lpcr_hv(struct kvmppc_vcore *vc,
+			unsigned long lpcr);
 extern void kvmppc_update_lpcr(struct kvm *kvm, unsigned long lpcr,
 			unsigned long mask);
 extern void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr);
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 13bad6bf4c95..c4539c38c639 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1635,6 +1635,27 @@ static int kvm_arch_vcpu_ioctl_set_sregs_hv(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
+/*
+ * Enforce limits on guest LPCR values based on hardware availability,
+ * guest configuration, and possibly hypervisor support and security
+ * concerns.
+ */
+unsigned long kvmppc_filter_lpcr_hv(struct kvmppc_vcore *vc, unsigned long lpcr)
+{
+	/* On POWER8 and above, userspace can modify AIL */
+	if (!cpu_has_feature(CPU_FTR_ARCH_207S))
+		lpcr &= ~LPCR_AIL;
+
+	/*
+	 * On POWER9, allow userspace to enable large decrementer for the
+	 * guest, whether or not the host has it enabled.
+	 */
+	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+		lpcr &= ~LPCR_LD;
+
+	return lpcr;
+}
+
 static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
 		bool preserve_top32)
 {
@@ -1643,6 +1664,23 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
 	u64 mask;
 
 	spin_lock(&vc->lock);
+
+	/*
+	 * Userspace can only modify
+	 * DPFD (default prefetch depth), ILE (interrupt little-endian),
+	 * TC (translation control), AIL (alternate interrupt location),
+	 * LD (large decrementer).
+	 * These are subject to restrictions from kvmppc_filter_lcpr_hv().
+	 */
+	mask = LPCR_DPFD | LPCR_ILE | LPCR_TC | LPCR_AIL | LPCR_LD;
+
+	/* Broken 32-bit version of LPCR must not clear top bits */
+	if (preserve_top32)
+		mask &= 0xFFFFFFFF;
+
+	new_lpcr = kvmppc_filter_lpcr_hv(vc,
+			(vc->lpcr & ~mask) | (new_lpcr & mask));
+
 	/*
 	 * If ILE (interrupt little-endian) has changed, update the
 	 * MSR_LE bit in the intr_msr for each vcpu in this vcore.
@@ -1661,25 +1699,8 @@ static void kvmppc_set_lpcr(struct kvm_vcpu *vcpu, u64 new_lpcr,
 		}
 	}
 
-	/*
-	 * Userspace can only modify DPFD (default prefetch depth),
-	 * ILE (interrupt little-endian) and TC (translation control).
-	 * On POWER8 and POWER9 userspace can also modify AIL (alt. interrupt loc.).
-	 */
-	mask = LPCR_DPFD | LPCR_ILE | LPCR_TC;
-	if (cpu_has_feature(CPU_FTR_ARCH_207S))
-		mask |= LPCR_AIL;
-	/*
-	 * On POWER9, allow userspace to enable large decrementer for the
-	 * guest, whether or not the host has it enabled.
-	 */
-	if (cpu_has_feature(CPU_FTR_ARCH_300))
-		mask |= LPCR_LD;
+	vc->lpcr = new_lpcr;
 
-	/* Broken 32-bit version of LPCR must not clear top bits */
-	if (preserve_top32)
-		mask &= 0xFFFFFFFF;
-	vc->lpcr = (vc->lpcr & ~mask) | (new_lpcr & mask);
 	spin_unlock(&vc->lock);
 }
 
@@ -4641,8 +4662,9 @@ void kvmppc_update_lpcr(struct kvm *kvm, unsigned long lpcr, unsigned long mask)
 		struct kvmppc_vcore *vc = kvm->arch.vcores[i];
 		if (!vc)
 			continue;
+
 		spin_lock(&vc->lock);
-		vc->lpcr = (vc->lpcr & ~mask) | lpcr;
+		vc->lpcr = kvmppc_filter_lpcr_hv(vc, (vc->lpcr & ~mask) | lpcr);
 		spin_unlock(&vc->lock);
 		if (++cores_done >= kvm->arch.online_vcores)
 			break;
diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index 2fe1fea4c934..f7b441b3eb17 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -142,7 +142,8 @@ static void sanitise_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr)
 	 */
 	mask = LPCR_DPFD | LPCR_ILE | LPCR_TC | LPCR_AIL | LPCR_LD |
 		LPCR_LPES | LPCR_MER;
-	hr->lpcr = (vc->lpcr & ~mask) | (hr->lpcr & mask);
+	hr->lpcr = kvmppc_filter_lpcr_hv(vc,
+			(vc->lpcr & ~mask) | (hr->lpcr & mask));
 
 	/*
 	 * Don't let L1 enable features for L2 which we've disabled for L1,
-- 
2.23.0