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Thu, 19 Mar 2026 13:26:06 -0700 (PDT) Received: from LQ5W56KC4T ([2001:8a0:672f:7800:e0e1:55cd:f0b:b1e5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b644ae16fsm1347544f8f.8.2026.03.19.13.26.05 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 19 Mar 2026 13:26:05 -0700 (PDT) From: Eric Curtin X-Google-Original-From: Eric Curtin To: linux-hyperv@vger.kernel.org Cc: linux-kernel@vger.kernel.org, iourit@linux.microsoft.com, wei.liu@kernel.org, decui@microsoft.com, haiyangz@microsoft.com Subject: [PATCH 47/55] drivers: hv: dxgkrnl: Retry sending a VM bus packet when there is no place in the ring buffer Date: Thu, 19 Mar 2026 20:25:01 +0000 Message-ID: <20260319202509.63802-48-eric.curtin@docker.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260319202509.63802-1-eric.curtin@docker.com> References: <20260319202509.63802-1-eric.curtin@docker.com> Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Iouri Tarassov When D3DKMT requests are sent too quickly, the VM bus ring buffer could be full when a message is submitted. The change adds sleep and re-try count to handle this condition. Signed-off-by: Iouri Tarassov [kms: forward port to 6.6 from 6.1. No code changes made.] Signed-off-by: Kelsey Steele --- drivers/hv/dxgkrnl/dxgvmbus.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/drivers/hv/dxgkrnl/dxgvmbus.c b/drivers/hv/dxgkrnl/dxgvmbus.c index 67f55f4bf41d..467e7707c8c7 100644 --- a/drivers/hv/dxgkrnl/dxgvmbus.c +++ b/drivers/hv/dxgkrnl/dxgvmbus.c @@ -420,6 +420,7 @@ int dxgvmb_send_sync_msg(struct dxgvmbuschannel *channel, struct dxgvmbuspacket *packet = NULL; struct dxgkvmb_command_vm_to_host *cmd1; struct dxgkvmb_command_vgpu_to_host *cmd2; + int try_count = 0; if (cmd_size > DXG_MAX_VM_BUS_PACKET_SIZE || result_size > DXG_MAX_VM_BUS_PACKET_SIZE) { @@ -453,9 +454,19 @@ int dxgvmb_send_sync_msg(struct dxgvmbuschannel *channel, list_add_tail(&packet->packet_list_entry, &channel->packet_list_head); spin_unlock_irq(&channel->packet_list_mutex); - ret = vmbus_sendpacket(channel->channel, command, cmd_size, - packet->request_id, VM_PKT_DATA_INBAND, - VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED); + do { + ret = vmbus_sendpacket(channel->channel, command, cmd_size, + packet->request_id, VM_PKT_DATA_INBAND, + VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED); + /* + * -EAGAIN is returned when the VM bus ring buffer if full. + * Wait 2ms to allow the host to process messages and try again. + */ + if (ret == -EAGAIN) { + usleep_range(1000, 2000); + try_count++; + } + } while (ret == -EAGAIN && try_count < 50); if (ret) { DXG_ERR("vmbus_sendpacket failed: %x", ret); spin_lock_irq(&channel->packet_list_mutex);