[RFCv2 27/37] KVM: s390: protvirt: Only sync fmt4 registers

[Christian Borntraeger <borntraeger@de.ibm.com>]

From: Janosch Frank <frankja@linux.ibm.com>

A lot of the registers are controlled by the Ultravisor and never
visible to KVM. Also some registers are overlayed, like gbea is with
sidad, which might leak data to userspace.

Hence we sync a minimal set of registers for both SIE formats and then
check and sync format 2 registers if necessary.

Also we disable set/get one reg for the same reason. It's an old
interface anyway.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
[Fixes and patch splitting]
---
 arch/s390/kvm/kvm-s390.c | 116 ++++++++++++++++++++++++---------------
 1 file changed, 72 insertions(+), 44 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index b9692d722c1e..00a0ce4a3d35 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -3444,9 +3444,11 @@ static void kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
 	vcpu->arch.sie_block->gcr[0] = CR0_INITIAL_MASK;
 	vcpu->arch.sie_block->gcr[14] = CR14_INITIAL_MASK;
 	vcpu->run->s.regs.fpc = 0;
-	vcpu->arch.sie_block->gbea = 1;
-	vcpu->arch.sie_block->pp = 0;
-	vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
+	if (!kvm_s390_pv_handle_cpu(vcpu)) {
+		vcpu->arch.sie_block->gbea = 1;
+		vcpu->arch.sie_block->pp = 0;
+		vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
+	}
 }
 
 static void kvm_arch_vcpu_ioctl_clear_reset(struct kvm_vcpu *vcpu)
@@ -4057,25 +4059,16 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 	return rc;
 }
 
-static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
+static void sync_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
 	struct runtime_instr_cb *riccb;
 	struct gs_cb *gscb;
 
-	riccb = (struct runtime_instr_cb *) &kvm_run->s.regs.riccb;
-	gscb = (struct gs_cb *) &kvm_run->s.regs.gscb;
 	vcpu->arch.sie_block->gpsw.mask = kvm_run->psw_mask;
 	vcpu->arch.sie_block->gpsw.addr = kvm_run->psw_addr;
-	if (kvm_run->kvm_dirty_regs & KVM_SYNC_PREFIX)
-		kvm_s390_set_prefix(vcpu, kvm_run->s.regs.prefix);
-	if (kvm_run->kvm_dirty_regs & KVM_SYNC_CRS) {
-		memcpy(&vcpu->arch.sie_block->gcr, &kvm_run->s.regs.crs, 128);
-		/* some control register changes require a tlb flush */
-		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
-	}
+	riccb = (struct runtime_instr_cb *) &kvm_run->s.regs.riccb;
+	gscb = (struct gs_cb *) &kvm_run->s.regs.gscb;
 	if (kvm_run->kvm_dirty_regs & KVM_SYNC_ARCH0) {
-		kvm_s390_set_cpu_timer(vcpu, kvm_run->s.regs.cputm);
-		vcpu->arch.sie_block->ckc = kvm_run->s.regs.ckc;
 		vcpu->arch.sie_block->todpr = kvm_run->s.regs.todpr;
 		vcpu->arch.sie_block->pp = kvm_run->s.regs.pp;
 		vcpu->arch.sie_block->gbea = kvm_run->s.regs.gbea;
@@ -4116,6 +4109,47 @@ static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
 		vcpu->arch.sie_block->fpf |= kvm_run->s.regs.bpbc ? FPF_BPBC : 0;
 	}
+	if (MACHINE_HAS_GS) {
+		preempt_disable();
+		__ctl_set_bit(2, 4);
+		if (current->thread.gs_cb) {
+			vcpu->arch.host_gscb = current->thread.gs_cb;
+			save_gs_cb(vcpu->arch.host_gscb);
+		}
+		if (vcpu->arch.gs_enabled) {
+			current->thread.gs_cb = (struct gs_cb *)
+						&vcpu->run->s.regs.gscb;
+			restore_gs_cb(current->thread.gs_cb);
+		}
+		preempt_enable();
+	}
+	/* SIE will load etoken directly from SDNX and therefore kvm_run */
+}
+
+static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
+{
+	/*
+	 * at several places we have to modify our internal view to not do
+	 * things that are disallowed by the ultravisor. For example we must
+	 * not inject interrupts after specific exits (e.g. 112). We do this
+	 * by turning off the MIE bits of our PSW copy. To avoid getting
+	 * validity intercepts, we do only accept the condition code from
+	 * userspace.
+	 */
+	vcpu->arch.sie_block->gpsw.mask &= ~PSW_MASK_CC;
+	vcpu->arch.sie_block->gpsw.mask |= kvm_run->psw_mask & PSW_MASK_CC;
+
+	if (kvm_run->kvm_dirty_regs & KVM_SYNC_PREFIX)
+		kvm_s390_set_prefix(vcpu, kvm_run->s.regs.prefix);
+	if (kvm_run->kvm_dirty_regs & KVM_SYNC_CRS) {
+		memcpy(&vcpu->arch.sie_block->gcr, &kvm_run->s.regs.crs, 128);
+		/* some control register changes require a tlb flush */
+		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
+	}
+	if (kvm_run->kvm_dirty_regs & KVM_SYNC_ARCH0) {
+		kvm_s390_set_cpu_timer(vcpu, kvm_run->s.regs.cputm);
+		vcpu->arch.sie_block->ckc = kvm_run->s.regs.ckc;
+	}
 	save_access_regs(vcpu->arch.host_acrs);
 	restore_access_regs(vcpu->run->s.regs.acrs);
 	/* save host (userspace) fprs/vrs */
@@ -4130,23 +4164,31 @@ static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	if (test_fp_ctl(current->thread.fpu.fpc))
 		/* User space provided an invalid FPC, let's clear it */
 		current->thread.fpu.fpc = 0;
+
+	/* Sync fmt2 only data */
+	if (likely(!kvm_s390_pv_is_protected(vcpu->kvm)))
+		sync_regs_fmt2(vcpu, kvm_run);
+	kvm_run->kvm_dirty_regs = 0;
+}
+
+static void store_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
+{
+	kvm_run->s.regs.pp = vcpu->arch.sie_block->pp;
+	kvm_run->s.regs.gbea = vcpu->arch.sie_block->gbea;
+	kvm_run->s.regs.bpbc = (vcpu->arch.sie_block->fpf & FPF_BPBC) == FPF_BPBC;
 	if (MACHINE_HAS_GS) {
-		preempt_disable();
 		__ctl_set_bit(2, 4);
-		if (current->thread.gs_cb) {
-			vcpu->arch.host_gscb = current->thread.gs_cb;
-			save_gs_cb(vcpu->arch.host_gscb);
-		}
-		if (vcpu->arch.gs_enabled) {
-			current->thread.gs_cb = (struct gs_cb *)
-						&vcpu->run->s.regs.gscb;
-			restore_gs_cb(current->thread.gs_cb);
-		}
+		if (vcpu->arch.gs_enabled)
+			save_gs_cb(current->thread.gs_cb);
+		preempt_disable();
+		current->thread.gs_cb = vcpu->arch.host_gscb;
+		restore_gs_cb(vcpu->arch.host_gscb);
 		preempt_enable();
+		if (!vcpu->arch.host_gscb)
+			__ctl_clear_bit(2, 4);
+		vcpu->arch.host_gscb = NULL;
 	}
-	/* SIE will load etoken directly from SDNX and therefore kvm_run */
-
-	kvm_run->kvm_dirty_regs = 0;
+	/* SIE will save etoken directly into SDNX and therefore kvm_run */
 }
 
 static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
@@ -4158,12 +4200,9 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	kvm_run->s.regs.cputm = kvm_s390_get_cpu_timer(vcpu);
 	kvm_run->s.regs.ckc = vcpu->arch.sie_block->ckc;
 	kvm_run->s.regs.todpr = vcpu->arch.sie_block->todpr;
-	kvm_run->s.regs.pp = vcpu->arch.sie_block->pp;
-	kvm_run->s.regs.gbea = vcpu->arch.sie_block->gbea;
 	kvm_run->s.regs.pft = vcpu->arch.pfault_token;
 	kvm_run->s.regs.pfs = vcpu->arch.pfault_select;
 	kvm_run->s.regs.pfc = vcpu->arch.pfault_compare;
-	kvm_run->s.regs.bpbc = (vcpu->arch.sie_block->fpf & FPF_BPBC) == FPF_BPBC;
 	save_access_regs(vcpu->run->s.regs.acrs);
 	restore_access_regs(vcpu->arch.host_acrs);
 	/* Save guest register state */
@@ -4172,19 +4211,8 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	/* Restore will be done lazily at return */
 	current->thread.fpu.fpc = vcpu->arch.host_fpregs.fpc;
 	current->thread.fpu.regs = vcpu->arch.host_fpregs.regs;
-	if (MACHINE_HAS_GS) {
-		__ctl_set_bit(2, 4);
-		if (vcpu->arch.gs_enabled)
-			save_gs_cb(current->thread.gs_cb);
-		preempt_disable();
-		current->thread.gs_cb = vcpu->arch.host_gscb;
-		restore_gs_cb(vcpu->arch.host_gscb);
-		preempt_enable();
-		if (!vcpu->arch.host_gscb)
-			__ctl_clear_bit(2, 4);
-		vcpu->arch.host_gscb = NULL;
-	}
-	/* SIE will save etoken directly into SDNX and therefore kvm_run */
+	if (likely(!kvm_s390_pv_is_protected(vcpu->kvm)))
+		store_regs_fmt2(vcpu, kvm_run);
 }
 
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
-- 
2.24.0