powerpc/64s: Set reserved PCR bits

Currently the reserved bits of the Processor Compatibility
Register (PCR) are cleared as per the Programming Note in Section
1.3.3 of version 3.0B of the Power ISA. This causes all new
architecture features to be made available when running on newer
processors with new architecture features added to the PCR as bits
must be set to disable a given feature.

For example to disable new features added as part of Version 2.07 of
the ISA the corresponding bit in the PCR needs to be set.

As new processor features generally require explicit kernel support
they should be disabled until such support is implemented. Therefore
kernels should set all unknown/reserved bits in the PCR such that any
new architecture features which the kernel does not currently know
about get disabled.

An update is planned to the ISA to clarify that the PCR is an
exception to the Programming Note on reserved bits in Section 1.3.3.

Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Tested-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190917004605.22471-2-alistair@popple.id.au

3 files changed, 16 insertions, 11 deletions

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index efd8f93bc9dc..709cf1fd4cf4 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -401,8 +401,11 @@ static int kvmppc_set_arch_compat(struct kvm_vcpu *vcpu, u32 arch_compat)
 
 	spin_lock(&vc->lock);
 	vc->arch_compat = arch_compat;
-	/* Set all PCR bits for which guest_pcr_bit <= bit < host_pcr_bit */
-	vc->pcr = host_pcr_bit - guest_pcr_bit;
+	/*
+	 * Set all PCR bits for which guest_pcr_bit <= bit < host_pcr_bit
+	 * Also set all reserved PCR bits
+	 */
+	vc->pcr = (host_pcr_bit - guest_pcr_bit) | PCR_MASK;
 	spin_unlock(&vc->lock);
 
 	return 0;
@@ -3410,7 +3413,7 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 	}
 
 	if (vc->pcr)
-		mtspr(SPRN_PCR, vc->pcr);
+		mtspr(SPRN_PCR, vc->pcr | PCR_MASK);
 	mtspr(SPRN_DPDES, vc->dpdes);
 	mtspr(SPRN_VTB, vc->vtb);
 
@@ -3490,7 +3493,7 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 	vc->vtb = mfspr(SPRN_VTB);
 	mtspr(SPRN_DPDES, 0);
 	if (vc->pcr)
-		mtspr(SPRN_PCR, 0);
+		mtspr(SPRN_PCR, PCR_MASK);
 
 	if (vc->tb_offset_applied) {
 		u64 new_tb = mftb() - vc->tb_offset_applied;
diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index fff90f2c3de2..cdf30c6eaf54 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -29,7 +29,7 @@ void kvmhv_save_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr)
 {
 	struct kvmppc_vcore *vc = vcpu->arch.vcore;
 
-	hr->pcr = vc->pcr;
+	hr->pcr = vc->pcr | PCR_MASK;
 	hr->dpdes = vc->dpdes;
 	hr->hfscr = vcpu->arch.hfscr;
 	hr->tb_offset = vc->tb_offset;
@@ -65,7 +65,7 @@ static void byteswap_hv_regs(struct hv_guest_state *hr)
 	hr->lpid = swab32(hr->lpid);
 	hr->vcpu_token = swab32(hr->vcpu_token);
 	hr->lpcr = swab64(hr->lpcr);
-	hr->pcr = swab64(hr->pcr);
+	hr->pcr = swab64(hr->pcr) | PCR_MASK;
 	hr->amor = swab64(hr->amor);
 	hr->dpdes = swab64(hr->dpdes);
 	hr->hfscr = swab64(hr->hfscr);
@@ -148,7 +148,7 @@ static void restore_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr)
 {
 	struct kvmppc_vcore *vc = vcpu->arch.vcore;
 
-	vc->pcr = hr->pcr;
+	vc->pcr = hr->pcr | PCR_MASK;
 	vc->dpdes = hr->dpdes;
 	vcpu->arch.hfscr = hr->hfscr;
 	vcpu->arch.dawr = hr->dawr0;
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 9a05b0d932ef..74a9cfe84aee 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -644,8 +644,10 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
 
 	/* Load guest PCR value to select appropriate compat mode */
 37:	ld	r7, VCORE_PCR(r5)
-	cmpdi	r7, 0
+	LOAD_REG_IMMEDIATE(r6, PCR_MASK)
+	cmpld	r7, r6
 	beq	38f
+	or	r7, r7, r6
 	mtspr	SPRN_PCR, r7
 38:
 
@@ -1913,10 +1915,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 
 	/* Reset PCR */
 	ld	r0, VCORE_PCR(r5)
-	cmpdi	r0, 0
+	LOAD_REG_IMMEDIATE(r6, PCR_MASK)
+	cmpld	r0, r6
 	beq	18f
-	li	r0, 0
-	mtspr	SPRN_PCR, r0
+	mtspr	SPRN_PCR, r6
 18:
 	/* Signal secondary CPUs to continue */
 	stb	r0,VCORE_IN_GUEST(r5)