On Mon, 2021-06-14 at 13:39 +1000, Nicholas Piggin wrote:

Excerpts from Haren Myneni's message of June 13, 2021 9:04 pm:

quoted

The hypervisor provides different capabilities that it supports
to define the user space NX request. These capabilities are
recommended minimum compression / decompression lengths and the
maximum request buffer size in bytes.

Changes to get NX overall capabilities which points to the
specific features that the hypervisor supports. Then retrieve
the capabilities for the specific feature (available only
for NXGZIP).

So what does this give you which you didn't have before? Should
this go before the previous patch that enables the interface for
guests,
or is there some functional-yet-degraded mode that is available
without
this patch?

I would suggest even if this is the case to switch ordering of the 
patches so as to reduce the matrix of functionality that userspace
sees 
when bisecting. Unless you specifically want this kind of
bisectability,
in which case make that explicit in the changelog.

Thanks for your suggestions. I will incorporate them and post next
revision. 

The user space request buffer length should not be more than
req_max_processed_len (available through sysfs). Otherwise NX will
return the request with RMA_Reject. Whereasas min_compress_len and
min_decompress_len are recommended values. 

We can add this patch and the last one (crypto/nx: Add sysfs interface
to export NX capabilities) before the actual enablement ("crypto/nx:
Register and unregisterVAS interface on PowerVM""

Thanks
Haren

Thanks,
Nick

quoted

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
---
 drivers/crypto/nx/nx-common-pseries.c | 86
+++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/drivers/crypto/nx/nx-common-pseries.c

b/drivers/crypto/nx/nx-common-pseries.c
index 9a40fca8a9e6..60b5049ec9f7 100644

--- a/drivers/crypto/nx/nx-common-pseries.c
+++ b/drivers/crypto/nx/nx-common-pseries.c

@@ -9,6 +9,7 @@
  */
 
 #include <asm/vio.h>
+#include <asm/hvcall.h>
 #include <asm/vas.h>
 
 #include "nx-842.h"

@@ -20,6 +21,29 @@ MODULE_DESCRIPTION("842 H/W Compression driver

for IBM Power processors");
 MODULE_ALIAS_CRYPTO("842");
 MODULE_ALIAS_CRYPTO("842-nx");
 
+/*
+ * Coprocessor type specific capabilities from the hypervisor.
+ */
+struct hv_nx_ct_caps {
+	__be64	descriptor;
+	__be64	req_max_processed_len;	/* Max bytes in one GZIP
request */
+	__be64	min_compress_len;	/* Min compression size in
bytes */
+	__be64	min_decompress_len;	/* Min decompression size
in bytes */
+} __packed __aligned(0x1000);
+
+/*
+ * Coprocessor type specific capabilities.
+ */
+struct nx_ct_caps {
+	u64	descriptor;
+	u64	req_max_processed_len;	/* Max bytes in one GZIP request */
+	u64	min_compress_len;	/* Min compression in bytes */
+	u64	min_decompress_len;	/* Min decompression in bytes */
+};
+
+static u64 caps_feat;
+static struct nx_ct_caps nx_ct_caps;
+
 static struct nx842_constraints nx842_pseries_constraints = {
 	.alignment =	DDE_BUFFER_ALIGN,
 	.multiple =	DDE_BUFFER_LAST_MULT,

@@ -1066,6 +1090,64 @@ static void nx842_remove(struct vio_dev

*viodev)
 	kfree(old_devdata);
 }
 
+/*
+ * Get NX capabilities from the hypervisor.
+ * Only NXGZIP capabilities are provided by the hypersvisor right
+ * now and these values are available to user space with sysfs.
+ */
+static void __init nxct_get_capabilities(void)
+{
+	struct hv_vas_all_caps *hv_caps;
+	struct hv_nx_ct_caps *hv_nxc;
+	int rc;
+
+	hv_caps = kmalloc(sizeof(*hv_caps), GFP_KERNEL);
+	if (!hv_caps)
+		return;
+	/*
+	 * Get NX overall capabilities with feature type=0
+	 */
+	rc = h_query_vas_capabilities(H_QUERY_NX_CAPABILITIES, 0,
+					  (u64)virt_to_phys(hv_caps));
+	if (rc)
+		goto out;
+
+	caps_feat = be64_to_cpu(hv_caps->feat_type);
+	/*
+	 * NX-GZIP feature available
+	 */
+	if (caps_feat & VAS_NX_GZIP_FEAT_BIT) {
+		hv_nxc = kmalloc(sizeof(*hv_nxc), GFP_KERNEL);
+		if (!hv_nxc)
+			goto out;
+		/*
+		 * Get capabilities for NX-GZIP feature
+		 */
+		rc = h_query_vas_capabilities(H_QUERY_NX_CAPABILITIES,
+						  VAS_NX_GZIP_FEAT,
+						  (u64)virt_to_phys(hv_
nxc));
+	} else {
+		pr_err("NX-GZIP feature is not available\n");
+		rc = -EINVAL;
+	}
+
+	if (!rc) {
+		nx_ct_caps.descriptor = be64_to_cpu(hv_nxc-

quoted

descriptor);

+		nx_ct_caps.req_max_processed_len =
+				be64_to_cpu(hv_nxc-

quoted

req_max_processed_len);

+		nx_ct_caps.min_compress_len =
+				be64_to_cpu(hv_nxc->min_compress_len);
+		nx_ct_caps.min_decompress_len =
+				be64_to_cpu(hv_nxc-

quoted

min_decompress_len);

+	} else {
+		caps_feat = 0;
+	}
+
+	kfree(hv_nxc);
+out:
+	kfree(hv_caps);
+}
+
 static const struct vio_device_id nx842_vio_driver_ids[] = {
 	{"ibm,compression-v1", "ibm,compression"},
 	{"", ""},

@@ -1093,6 +1175,10 @@ static int __init nx842_pseries_init(void)
 		return -ENOMEM;
 
 	RCU_INIT_POINTER(devdata, new_devdata);
+	/*
+	 * Get NX capabilities from the hypervisor.
+	 */
+	nxct_get_capabilities();
 
 	ret = vio_register_driver(&nx842_vio_driver);
 	if (ret) {

-- 
2.18.2