65 lines
2.4 KiB
Diff
65 lines
2.4 KiB
Diff
From ca0559e2350c618048f7caf80cb79c1259e7cfd2 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= <berrange@redhat.com>
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Date: Tue, 10 Jun 2025 13:37:06 +0100
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Subject: [PATCH] hw/scsi/megasas: skip automatic zero-init of large arrays
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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The 'megasas_dcmd_pd_get_list' and 'megasas_dcmd_get_properties'
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methods have 4k structs used for copying data from the device.
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Skip the automatic zero-init of this array to eliminate the
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performance overhead in the I/O hot path.
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The 'info' structs are manually initialized with memset(). The
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compiler ought to be intelligent enough to turn the memset()
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into a static initialization operation, and thus not duplicate
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the automatic zero-init. Replacing memset() with '{}' makes it
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unambiguous that the arrays are statically initialized.
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Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
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Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
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Message-id: 20250610123709.835102-29-berrange@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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hw/scsi/megasas.c | 7 ++-----
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1 file changed, 2 insertions(+), 5 deletions(-)
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diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
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index 55cd188bd5..844643d916 100644
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--- a/hw/scsi/megasas.c
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+++ b/hw/scsi/megasas.c
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@@ -981,13 +981,11 @@ static int megasas_event_wait(MegasasState *s, MegasasCmd *cmd)
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static int megasas_dcmd_pd_get_list(MegasasState *s, MegasasCmd *cmd)
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{
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- struct mfi_pd_list info;
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- size_t dcmd_size = sizeof(info);
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+ struct mfi_pd_list info = {};
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BusChild *kid;
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uint32_t offset, dcmd_limit, num_pd_disks = 0, max_pd_disks;
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dma_addr_t residual;
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- memset(&info, 0, dcmd_size);
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offset = 8;
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dcmd_limit = offset + sizeof(struct mfi_pd_address);
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if (cmd->iov_size < dcmd_limit) {
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@@ -1429,11 +1427,10 @@ static int megasas_dcmd_cfg_read(MegasasState *s, MegasasCmd *cmd)
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static int megasas_dcmd_get_properties(MegasasState *s, MegasasCmd *cmd)
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{
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- struct mfi_ctrl_props info;
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+ struct mfi_ctrl_props info = {};
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size_t dcmd_size = sizeof(info);
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dma_addr_t residual;
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- memset(&info, 0x0, dcmd_size);
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if (cmd->iov_size < dcmd_size) {
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trace_megasas_dcmd_invalid_xfer_len(cmd->index, cmd->iov_size,
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dcmd_size);
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--
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2.47.3
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