linux-kernel - [PATCH v1 4/4] s390/kvm: VSIE: correctly handle MVPG when in VSIE

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Date:   Fri, 18 Dec 2020 15:18:11 +0100
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     borntraeger@...ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        stable@...r.kernel.org
Subject: [PATCH v1 4/4] s390/kvm: VSIE: correctly handle MVPG when in VSIE

Correctly handle the MVPG instruction when issued by a VSIE guest.

Fixes: a3508fbe9dc6d ("KVM: s390: vsie: initial support for nested virtualization")
Cc: stable@...r.kernel.org
Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
---
 arch/s390/kvm/vsie.c | 73 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index ada49583e530..6c3069868acd 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -977,6 +977,75 @@ static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	return 0;
 }
 
+static u64 vsie_get_register(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page, u8 reg)
+{
+	reg &= 0xf;
+	switch (reg) {
+	case 15:
+		return vsie_page->scb_s.gg15;
+	case 14:
+		return vsie_page->scb_s.gg14;
+	default:
+		return vcpu->run->s.regs.gprs[reg];
+	}
+}
+
+static int vsie_handle_mvpg(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
+{
+	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
+	unsigned long r1, r2, mask = PAGE_MASK;
+	int rc;
+
+	if (psw_bits(scb_s->gpsw).eaba == PSW_BITS_AMODE_24BIT)
+		mask = 0xfff000;
+	else if (psw_bits(scb_s->gpsw).eaba == PSW_BITS_AMODE_31BIT)
+		mask = 0x7ffff000;
+
+	r1 = vsie_get_register(vcpu, vsie_page, scb_s->ipb >> 20) & mask;
+	r2 = vsie_get_register(vcpu, vsie_page, scb_s->ipb >> 16) & mask;
+	rc = kvm_s390_vsie_mvpg_check(vcpu, r1, r2, &vsie_page->scb_o->mcic);
+
+	/*
+	 * Guest translation was not successful. The host needs to forward
+	 * the intercept to the guest and let the guest fix its page tables.
+	 * The guest needs then to retry the instruction.
+	 */
+	if (rc == -ENOENT)
+		return 1;
+
+	retry_vsie_icpt(vsie_page);
+
+	/*
+	 * Guest translation was not successful. The page tables of the guest
+	 * are broken. Try again and let the hardware deliver the fault.
+	 */
+	if (rc == -EFAULT)
+		return 0;
+
+	/*
+	 * Guest translation was successful. The host needs to fix up its
+	 * page tables and retry the instruction in the nested guest.
+	 * In case of failure, the instruction will intercept again, and
+	 * a different path will be taken.
+	 */
+	if (!rc) {
+		kvm_s390_shadow_fault(vcpu, vsie_page->gmap, r2);
+		kvm_s390_shadow_fault(vcpu, vsie_page->gmap, r1);
+		return 0;
+	}
+
+	/*
+	 * An exception happened during guest translation, it needs to be
+	 * delivered to the guest. This can happen if the host has EDAT1
+	 * enabled and the guest has not, or for other causes. The guest
+	 * needs to process the exception and return to the nested guest.
+	 */
+	if (rc > 0)
+		return kvm_s390_inject_prog_cond(vcpu, rc);
+
+	return 1;
+}
+
 /*
  * Run the vsie on a shadow scb and a shadow gmap, without any further
  * sanity checks, handling SIE faults.
@@ -1063,6 +1132,10 @@ static int do_vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 		if ((scb_s->ipa & 0xf000) != 0xf000)
 			scb_s->ipa += 0x1000;
 		break;
+	case ICPT_PARTEXEC:
+		if (scb_s->ipa == 0xb254)
+			rc = vsie_handle_mvpg(vcpu, vsie_page);
+		break;
 	}
 	return rc;
 }
-- 
2.26.2