powerpc/perf/hv-24x7: use kmem_cache instead of aligned stack allocations

Ian pointed out the use of __aligned(4096) caused rather large stack
consumption in single_24x7_request(), so use the kmem_cache
hv_page_cache (which we've already got set up for other allocations)
insead of allocating locally.

CC: Haren Myneni <hbabu@us.ibm.com>
Reported-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Cody P Schafer <dev@codyps.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 37 insertions, 18 deletions

diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
index 70d4f748b54b..697759d8eb16 100644
--- a/arch/powerpc/perf/hv-24x7.c
+++ b/arch/powerpc/perf/hv-24x7.c
@@ -294,7 +294,7 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
                                          u16 lpar, u64 *res,
                                          bool success_expected)
 {
-        unsigned long ret;
+        unsigned long ret = -ENOMEM;
 
         /*
          * request_buffer and result_buffer are not required to be 4k aligned,
@@ -304,7 +304,27 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
         struct reqb {
                 struct hv_24x7_request_buffer buf;
                 struct hv_24x7_request req;
-        } __packed __aligned(4096) request_buffer = {
+        } __packed *request_buffer;
+
+        struct {
+                struct hv_24x7_data_result_buffer buf;
+                struct hv_24x7_result res;
+                struct hv_24x7_result_element elem;
+                __be64 result;
+        } __packed *result_buffer;
+
+        BUILD_BUG_ON(sizeof(*request_buffer) > 4096);
+        BUILD_BUG_ON(sizeof(*result_buffer) > 4096);
+
+        request_buffer = kmem_cache_zalloc(hv_page_cache, GFP_USER);
+        if (!request_buffer)
+                goto out;
+
+        result_buffer = kmem_cache_zalloc(hv_page_cache, GFP_USER);
+        if (!result_buffer)
+                goto out_free_request_buffer;
+
+        *request_buffer = (struct reqb) {
                 .buf = {
                         .interface_version = HV_24X7_IF_VERSION_CURRENT,
                         .num_requests = 1,
@@ -320,28 +340,27 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
                 }
         };
 
-        struct resb {
-                struct hv_24x7_data_result_buffer buf;
-                struct hv_24x7_result res;
-                struct hv_24x7_result_element elem;
-                __be64 result;
-        } __packed __aligned(4096) result_buffer = {};
-
         ret = plpar_hcall_norets(H_GET_24X7_DATA,
-                        virt_to_phys(&request_buffer), sizeof(request_buffer),
-                        virt_to_phys(&result_buffer),  sizeof(result_buffer));
+                        virt_to_phys(request_buffer), sizeof(*request_buffer),
+                        virt_to_phys(result_buffer),  sizeof(*result_buffer));
 
         if (ret) {
                 if (success_expected)
-                        pr_err_ratelimited("hcall failed: %d %#x %#x %d => 0x%lx (%ld) detail=0x%x failing ix=%x\n",
-                                        domain, offset, ix, lpar,
-                                        ret, ret,
-                                        result_buffer.buf.detailed_rc,
-                                        result_buffer.buf.failing_request_ix);
-                return ret;
+                        pr_err_ratelimited("hcall failed: %d %#x %#x %d => "
+                                "0x%lx (%ld) detail=0x%x failing ix=%x\n",
+                                domain, offset, ix, lpar, ret, ret,
+                                result_buffer->buf.detailed_rc,
+                                result_buffer->buf.failing_request_ix);
+                goto out_free_result_buffer;
         }
 
-        *res = be64_to_cpu(result_buffer.result);
+        *res = be64_to_cpu(result_buffer->result);
+
+out_free_result_buffer:
+        kfree(result_buffer);
+out_free_request_buffer:
+        kfree(request_buffer);
+out:
         return ret;
 }