From 3fafd694cf5df4fa7a9f4f48aad86748d18bd15a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Tue, 10 Jun 2025 13:37:03 +0100 Subject: [PATCH 33/43] hw/ppc/spapr_tpm_proxy: skip automatic zero-init of large arrays MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Stefan Hajnoczi RH-MergeRequest: 381: Solve -ftrivial-auto-var-init performance regression with QEMU_UNINITIALIZED RH-Jira: RHEL-95479 RH-Acked-by: Miroslav Rezanina RH-Commit: [25/31] fe7e91a1f74a696e03336cf3429042681c77c4c7 (stefanha/centos-stream-qemu-kvm) The 'tpm_execute' method has a pair of 4k arrays used for copying data between guest and host. Skip the automatic zero-init of these arrays to eliminate the performance overhead in the I/O hot path. The two arrays will be fully initialized when reading data from guest memory or reading data from the proxy FD. Signed-off-by: Daniel P. Berrangé Reviewed-by: Stefan Hajnoczi Reviewed-by: Klaus Jensen Reviewed-by: Harsh Prateek Bora Message-id: 20250610123709.835102-26-berrange@redhat.com Signed-off-by: Stefan Hajnoczi (cherry picked from commit 5dd9087fff74b5672526cad254e76f790fb35c7a) Signed-off-by: Stefan Hajnoczi --- hw/ppc/spapr_tpm_proxy.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/hw/ppc/spapr_tpm_proxy.c b/hw/ppc/spapr_tpm_proxy.c index ceaa0acaa1..7472ff8709 100644 --- a/hw/ppc/spapr_tpm_proxy.c +++ b/hw/ppc/spapr_tpm_proxy.c @@ -41,8 +41,8 @@ static ssize_t tpm_execute(SpaprTpmProxy *tpm_proxy, target_ulong *args) target_ulong data_in_size = args[2]; uint64_t data_out = ppc64_phys_to_real(args[3]); target_ulong data_out_size = args[4]; - uint8_t buf_in[TPM_SPAPR_BUFSIZE]; - uint8_t buf_out[TPM_SPAPR_BUFSIZE]; + QEMU_UNINITIALIZED uint8_t buf_in[TPM_SPAPR_BUFSIZE]; + QEMU_UNINITIALIZED uint8_t buf_out[TPM_SPAPR_BUFSIZE]; ssize_t ret; trace_spapr_tpm_execute(data_in, data_in_size, data_out, data_out_size); -- 2.39.3