linux-kernel - [PATCH v1 11/11] KVM: s390: pv: add support for UV feature bits

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Date:   Mon, 17 May 2021 22:07:58 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     kvm@...r.kernel.org
Cc:     cohuck@...hat.com, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, david@...hat.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 11/11] KVM: s390: pv: add support for UV feature bits

Add support for Ultravisor feature bits, and take advantage of the
functionality advertised to speed up the lazy destroy mechanism.

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
---
 arch/s390/boot/uv.c        | 1 +
 arch/s390/include/asm/uv.h | 9 ++++++++-
 arch/s390/kernel/uv.c      | 3 ++-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/s390/boot/uv.c b/arch/s390/boot/uv.c
index 87641dd65ccf..efdb55364919 100644
--- a/arch/s390/boot/uv.c
+++ b/arch/s390/boot/uv.c
@@ -36,6 +36,7 @@ void uv_query_info(void)
 		uv_info.max_sec_stor_addr = ALIGN(uvcb.max_guest_stor_addr, PAGE_SIZE);
 		uv_info.max_num_sec_conf = uvcb.max_num_sec_conf;
 		uv_info.max_guest_cpu_id = uvcb.max_guest_cpu_id;
+		uv_info.feature_bits = uvcb.uv_feature_bits;
 	}
 
 #ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index 1de5ff5e192a..808c2f0e0d7c 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -73,6 +73,11 @@ enum uv_cmds_inst {
 	BIT_UVC_CMD_UNPIN_PAGE_SHARED = 22,
 };
 
+/* Bits in uv features field */
+enum uv_features {
+	BIT_UVC_FEAT_MISC_0 = 0,
+};
+
 struct uv_cb_header {
 	u16 len;
 	u16 cmd;	/* Command Code */
@@ -97,7 +102,8 @@ struct uv_cb_qui {
 	u64 max_guest_stor_addr;
 	u8  reserved88[158 - 136];
 	u16 max_guest_cpu_id;
-	u8  reserveda0[200 - 160];
+	u64 uv_feature_bits;
+	u8  reserveda0[200 - 168];
 } __packed __aligned(8);
 
 /* Initialize Ultravisor */
@@ -274,6 +280,7 @@ struct uv_info {
 	unsigned long max_sec_stor_addr;
 	unsigned int max_num_sec_conf;
 	unsigned short max_guest_cpu_id;
+	unsigned long feature_bits;
 };
 
 extern struct uv_info uv_info;
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index 434d81baceed..b1fa38d5c388 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -291,7 +291,8 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
 
 static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm)
 {
-	return uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
+	return !test_bit_inv(BIT_UVC_FEAT_MISC_0, &uv_info.feature_bits) &&
+		uvcb->cmd != UVC_CMD_UNPIN_PAGE_SHARED &&
 		atomic_read(&mm->context.is_protected) > 1;
 }
 
-- 
2.31.1