[PATCH v6 15/21] KVM: s390: vsie: Add struct vsie_sca with pin and unpin methods

[Christoph Schlameuss <schlameuss@linux.ibm.com>]

Introduce the struct vsie_sca to hold the SSCA and required management
data along with alloc and free methods to use with the struct.
On this basis we can also add methods {,un}pin_sca() to simplify the
pinning SCAs in g1.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host_s390_types.h |   1 +
 arch/s390/kvm/s390/vsie.c                   | 101 +++++++++++++++++++++++++++-
 2 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/kvm_host_s390_types.h b/arch/s390/include/asm/kvm_host_s390_types.h
index 0b69e71bc8ee..1ac31a54d508 100644
--- a/arch/s390/include/asm/kvm_host_s390_types.h
+++ b/arch/s390/include/asm/kvm_host_s390_types.h
@@ -7,6 +7,7 @@
 #include <linux/types.h>
 
 #define KVM_S390_MAX_VSIE_VCPUS 256
+#define KVM_S390_MAX_SCA_PAGES 5
 
 #define KVM_S390_BSCA_CPU_SLOTS 64
 #define KVM_S390_ESCA_CPU_SLOTS 248
diff --git a/arch/s390/kvm/s390/vsie.c b/arch/s390/kvm/s390/vsie.c
index d52c3a42aa27..69334d4a3231 100644
--- a/arch/s390/kvm/s390/vsie.c
+++ b/arch/s390/kvm/s390/vsie.c
@@ -62,7 +62,8 @@ struct vsie_page {
 	gpa_t scb_gpa;				/* 0x0258 */
 	/* the shadow gmap in use by the vsie_page */
 	struct gmap_cache gmap_cache;		/* 0x0260 */
-	__u8 reserved[0x06f8 - 0x0278];		/* 0x0278 */
+	struct vsie_sca *vsie_sca;		/* 0x0278 */
+	__u8 reserved[0x06f8 - 0x0280];		/* 0x0280 */
 	struct kvm_s390_crypto_cb crycb;	/* 0x06f8 */
 	__u8 fac[8 + S390_ARCH_FAC_LIST_SIZE_BYTE];/* 0x07f8 */
 };
@@ -76,6 +77,36 @@ struct kvm_address_pair {
 	hpa_t hpa;
 };
 
+enum vsie_sca_flags {
+	VSIE_SCA_ESCA = 0,
+	VSIE_SCA_SCA_PINNED = 1,
+};
+
+struct vsie_sca {
+	struct_group(head,
+		struct ssca_block	ssca;
+	);
+	struct_group(keep,
+		struct vsie_page	*pages[KVM_S390_MAX_VSIE_VCPUS];
+		/* The mutex is used to synchronize access to the pages[] */
+		struct mutex		mutex;
+		atomic_t		ref_count;
+	);
+	struct_group(tail,
+		gpa_t			sca_gpa;
+		unsigned long		flags;
+		u64			mcn[4];
+		unsigned int		sca_o_nr_pages;
+		struct kvm_address_pair	sca_o_pages[KVM_S390_MAX_SCA_PAGES];
+	);
+};
+
+/*
+ * SSCA needs to be 32-byte aligned and members before the cpu field need to be on the same page.
+ * Forcing it to offset 0 will always fulfill the requirements.
+ */
+static_assert(!(offsetof(struct vsie_sca, ssca)));
+
 static inline bool sie_uses_esca(struct kvm_s390_sie_block *scb)
 {
 	return (scb->ecb2 & ECB2_ESCA);
@@ -859,6 +890,74 @@ static int pin_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	return 0;
 }
 
+/*
+ * Unpin g2 original sca in g1 memory.
+ *
+ * Called with vsie_sca_lock held in write, except in the destroy path.
+ */
+static void unpin_sca(struct kvm *kvm, struct vsie_sca *vsie_sca)
+{
+	if (!test_bit(VSIE_SCA_SCA_PINNED, &vsie_sca->flags))
+		return;
+
+	unpin_guest_pages(kvm, vsie_sca->sca_o_pages, vsie_sca->sca_o_nr_pages);
+	vsie_sca->sca_o_nr_pages = 0;
+
+	clear_bit(VSIE_SCA_SCA_PINNED, &vsie_sca->flags);
+}
+
+/*
+ * Pin g2 original sca in g1 memory.
+ *
+ * Called with vsie_sca_lock held in write.
+ */
+static int pin_sca(struct kvm *kvm, struct vsie_sca *vsie_sca)
+{
+	bool is_esca = test_bit(VSIE_SCA_ESCA, &vsie_sca->flags);
+	gpa_t offset = vsie_sca->sca_gpa & ~PAGE_MASK;
+	int rc, nr_pages;
+
+	if (test_bit(VSIE_SCA_SCA_PINNED, &vsie_sca->flags))
+		return 0;
+
+	if (is_esca) {
+		nr_pages = 4;
+		if (offset + sizeof(struct esca_block) > 4 * PAGE_SIZE)
+			nr_pages = 5;
+	} else {
+		nr_pages = 1;
+		if (offset + sizeof(struct bsca_block) > PAGE_SIZE)
+			nr_pages = 2;
+	}
+
+	rc = pin_guest_pages(kvm, vsie_sca->sca_gpa, nr_pages, vsie_sca->sca_o_pages,
+			     &vsie_sca->sca_o_nr_pages);
+	if (rc)
+		return rc;
+	set_bit(VSIE_SCA_SCA_PINNED, &vsie_sca->flags);
+
+	return 0;
+}
+
+static void free_vsie_sca(struct kvm *kvm, struct vsie_sca *vsie_sca)
+{
+	free_pages_exact(vsie_sca, sizeof(*vsie_sca));
+}
+
+static struct vsie_sca *alloc_vsie_sca(void)
+{
+	struct vsie_sca *vsie_sca;
+
+	vsie_sca = alloc_pages_exact(sizeof(*vsie_sca), GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+	if (!vsie_sca)
+		return NULL;
+
+	mutex_init(&vsie_sca->mutex);
+	atomic_set(&vsie_sca->ref_count, 0);
+
+	return vsie_sca;
+}
+
 void kvm_s390_vsie_gmap_notifier(struct gmap *gmap, gpa_t start, gpa_t end)
 {
 	struct vsie_page *cur, *next;

-- 
2.55.0