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    Subject[PATCH 02/16] powerpc/perf/hv-24x7: use kmem_cache instead of aligned stack allocations
    Date
    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: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
    Reported-by: Ian Munsie <imunsie@au1.ibm.com>
    Signed-off-by: Cody P Schafer <dev@codyps.com>
    ---
    arch/powerpc/perf/hv-24x7.c | 52 ++++++++++++++++++++++++++++++++-------------
    1 file changed, 37 insertions(+), 15 deletions(-)

    diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c
    index e0766b8..9a7a830 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 resb {
    + 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_alloc(hv_page_cache, GFP_USER);
    +
    + if (!request_buffer)
    + goto out_reqb;
    +
    + result_buffer = kmem_cache_zalloc(hv_page_cache, GFP_USER);
    + if (!result_buffer)
    + goto out_resb;
    +
    + *request_buffer = (struct reqb) {
    .buf = {
    .interface_version = HV_24X7_IF_VERSION_CURRENT,
    .num_requests = 1,
    @@ -320,28 +340,30 @@ 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;
    + result_buffer->buf.detailed_rc,
    + result_buffer->buf.failing_request_ix);
    + goto out_hcall;
    }

    - *res = be64_to_cpu(result_buffer.result);
    + *res = be64_to_cpu(result_buffer->result);
    + kfree(result_buffer);
    + kfree(request_buffer);
    + return ret;
    +
    +out_hcall:
    + kfree(result_buffer);
    +out_resb:
    + kfree(request_buffer);
    +out_reqb:
    return ret;
    }

    --
    1.9.3


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