From: Daniel P. Berrangé <berrange@redhat.com>
Date: Tue, 10 Jun 2025 12:37:04 +0000 (+0100)
Subject: hw/usb/hcd-ohci: skip automatic zero-init of large array
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=14997d521d1cd0bb36c902ef1032f0d3f2a3c912;p=thirdparty%2Fqemu.git

hw/usb/hcd-ohci: skip automatic zero-init of large array

The 'ohci_service_iso_td' method has a 8k byte array used for copying
data between guest and host. Skip the automatic zero-init of this
array to eliminate the performance overhead in the I/O hot path.

The 'buf' array will be fully initialized when reading data from guest
memory.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Message-id: 20250610123709.835102-27-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---

diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
index 71b54914d3..72a9f9f474 100644
--- a/hw/usb/hcd-ohci.c
+++ b/hw/usb/hcd-ohci.c
@@ -577,7 +577,7 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed)
     USBDevice *dev;
     USBEndpoint *ep;
     USBPacket *pkt;
-    uint8_t buf[8192];
+    QEMU_UNINITIALIZED uint8_t buf[8192];
     bool int_req;
     struct ohci_iso_td iso_td;
     uint32_t addr;