From patchwork Thu Sep 7 03:42:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Snow X-Patchwork-Id: 13376124 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 05314EE14D8 for ; Thu, 7 Sep 2023 03:44:21 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qe5up-000057-2a; Wed, 06 Sep 2023 23:42:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qe5un-0008Vw-NY for qemu-devel@nongnu.org; Wed, 06 Sep 2023 23:42:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qe5ul-0007Yz-5L for qemu-devel@nongnu.org; Wed, 06 Sep 2023 23:42:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1694058161; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8Kd5tMpalOgxIp7itrv0DFlWsnmvAtiGth05JMj/vNA=; b=efgJ2b4pdBgD3v2S2C3KkF1FvClmCcKN1ShKpPtNaYW8+N2mvJlpHlEm0qmVcP5lUm7++7 7JCJtxKnyDFBZ5TMIDyp0RO124ADrliMoIfqE8prtia4TI4l75XsxOQMCoHOH+OByPfkBi sOl+wINu+Dw2jRXjov6ktTmvC0WNKzE= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-307-CTD1XCTfN1-yH3AsuUyVzQ-1; Wed, 06 Sep 2023 23:42:30 -0400 X-MC-Unique: CTD1XCTfN1-yH3AsuUyVzQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1E51B3C0EAA7; Thu, 7 Sep 2023 03:42:30 +0000 (UTC) Received: from scv.redhat.com (unknown [10.22.8.43]) by smtp.corp.redhat.com (Postfix) with ESMTP id C8FDD1182E7; Thu, 7 Sep 2023 03:42:29 +0000 (UTC) From: John Snow To: qemu-devel@nongnu.org Cc: Thomas Huth , John Snow , Laurent Vivier , qemu-block@nongnu.org, Paolo Bonzini , Niklas Cassel Subject: [PULL for-6.2 3/7] hw/ide/ahci: simplify and document PxCI handling Date: Wed, 6 Sep 2023 23:42:24 -0400 Message-ID: <20230907034228.4054839-4-jsnow@redhat.com> In-Reply-To: <20230907034228.4054839-1-jsnow@redhat.com> References: <20230907034228.4054839-1-jsnow@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Niklas Cassel The AHCI spec states that: For NCQ, PxCI is cleared on command queued successfully. For non-NCQ, PxCI is cleared on command completed successfully. (A non-NCQ command that completes with error does not clear PxCI.) The current QEMU implementation either clears PxCI in check_cmd(), or in ahci_cmd_done(). check_cmd() will clear PxCI for a command if handle_cmd() returns 0. handle_cmd() will return -1 if BUSY or DRQ is set. The QEMU implementation for NCQ commands will currently not set BUSY or DRQ, so they will always have PxCI cleared by handle_cmd(). ahci_cmd_done() will never even get called for NCQ commands. Non-NCQ commands are executed by ide_bus_exec_cmd(). Non-NCQ commands in QEMU are implemented either in a sync or in an async way. For non-NCQ commands implemented in a sync way, the command handler will return true, and when ide_bus_exec_cmd() sees that a command handler returns true, it will call ide_cmd_done() (which will call ahci_cmd_done()). For a command implemented in a sync way, ahci_cmd_done() will do nothing (since busy_slot is not set). Instead, after ide_bus_exec_cmd() has finished, check_cmd() will clear PxCI for these commands. For non-NCQ commands implemented in an async way (using either aiocb or pio_aiocb), the command handler will return false, ide_bus_exec_cmd() will not call ide_cmd_done(), instead it is expected that the async callback function will call ide_cmd_done() once the async command is done. handle_cmd() will set busy_slot, if and only if BUSY or DRQ is set, and this is checked _after_ ide_bus_exec_cmd() has returned. handle_cmd() will return -1, so check_cmd() will not clear PxCI. When the async callback calls ide_cmd_done() (which will call ahci_cmd_done()), it will see that busy_slot is set, and ahci_cmd_done() will clear PxCI. This seems racy, since busy_slot is set _after_ ide_bus_exec_cmd() has returned. The callback might come before busy_slot gets set. And it is quite confusing that ahci_cmd_done() will be called for all non-NCQ commands when the command is done, but will only clear PxCI in certain cases, even though it will always write a D2H FIS and raise an IRQ. Even worse, in the case where ahci_cmd_done() does not clear PxCI, it still raises an IRQ. Host software might thus read an old PxCI value, since PxCI is cleared (by check_cmd()) after the IRQ has been raised. Try to simplify this by always setting busy_slot for non-NCQ commands, such that ahci_cmd_done() will always be responsible for clearing PxCI for non-NCQ commands. For NCQ commands, clear PxCI when we receive the D2H FIS, but before raising the IRQ, see AHCI 1.3.1, section 5.3.8, states RegFIS:Entry and RegFIS:ClearCI. Signed-off-by: Niklas Cassel Message-id: 20230609140844.202795-5-nks@flawful.org Signed-off-by: John Snow --- hw/ide/ahci.c | 70 ++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 50 insertions(+), 20 deletions(-) diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c index 4b272397fd..3deaf01add 100644 --- a/hw/ide/ahci.c +++ b/hw/ide/ahci.c @@ -41,9 +41,10 @@ #include "trace.h" static void check_cmd(AHCIState *s, int port); -static int handle_cmd(AHCIState *s, int port, uint8_t slot); +static void handle_cmd(AHCIState *s, int port, uint8_t slot); static void ahci_reset_port(AHCIState *s, int port); static bool ahci_write_fis_d2h(AHCIDevice *ad, bool d2h_fis_i); +static void ahci_clear_cmd_issue(AHCIDevice *ad, uint8_t slot); static void ahci_init_d2h(AHCIDevice *ad); static int ahci_dma_prepare_buf(const IDEDMA *dma, int32_t limit); static bool ahci_map_clb_address(AHCIDevice *ad); @@ -591,9 +592,8 @@ static void check_cmd(AHCIState *s, int port) if ((pr->cmd & PORT_CMD_START) && pr->cmd_issue) { for (slot = 0; (slot < 32) && pr->cmd_issue; slot++) { - if ((pr->cmd_issue & (1U << slot)) && - !handle_cmd(s, port, slot)) { - pr->cmd_issue &= ~(1U << slot); + if (pr->cmd_issue & (1U << slot)) { + handle_cmd(s, port, slot); } } } @@ -1123,6 +1123,22 @@ static void process_ncq_command(AHCIState *s, int port, const uint8_t *cmd_fis, return; } + /* + * A NCQ command clears the bit in PxCI after the command has been QUEUED + * successfully (ERROR not set, BUSY and DRQ cleared). + * + * For NCQ commands, PxCI will always be cleared here. + * + * (Once the NCQ command is COMPLETED, the device will send a SDB FIS with + * the interrupt bit set, which will clear PxSACT and raise an interrupt.) + */ + ahci_clear_cmd_issue(ad, slot); + + /* + * In reality, for NCQ commands, PxCI is cleared after receiving a D2H FIS + * without the interrupt bit set, but since ahci_write_fis_d2h() can raise + * an IRQ on error, we need to call them in reverse order. + */ ahci_write_fis_d2h(ad, false); ncq_tfs->used = 1; @@ -1197,6 +1213,7 @@ static void handle_reg_h2d_fis(AHCIState *s, int port, { IDEState *ide_state = &s->dev[port].port.ifs[0]; AHCICmdHdr *cmd = get_cmd_header(s, port, slot); + AHCIDevice *ad = &s->dev[port]; uint16_t opts = le16_to_cpu(cmd->opts); if (cmd_fis[1] & 0x0F) { @@ -1273,11 +1290,19 @@ static void handle_reg_h2d_fis(AHCIState *s, int port, /* Reset transferred byte counter */ cmd->status = 0; + /* + * A non-NCQ command clears the bit in PxCI after the command has COMPLETED + * successfully (ERROR not set, BUSY and DRQ cleared). + * + * For non-NCQ commands, PxCI will always be cleared by ahci_cmd_done(). + */ + ad->busy_slot = slot; + /* We're ready to process the command in FIS byte 2. */ ide_bus_exec_cmd(&s->dev[port].port, cmd_fis[2]); } -static int handle_cmd(AHCIState *s, int port, uint8_t slot) +static void handle_cmd(AHCIState *s, int port, uint8_t slot) { IDEState *ide_state; uint64_t tbl_addr; @@ -1288,12 +1313,12 @@ static int handle_cmd(AHCIState *s, int port, uint8_t slot) if (s->dev[port].port.ifs[0].status & (BUSY_STAT|DRQ_STAT)) { /* Engine currently busy, try again later */ trace_handle_cmd_busy(s, port); - return -1; + return; } if (!s->dev[port].lst) { trace_handle_cmd_nolist(s, port); - return -1; + return; } cmd = get_cmd_header(s, port, slot); /* remember current slot handle for later */ @@ -1303,7 +1328,7 @@ static int handle_cmd(AHCIState *s, int port, uint8_t slot) ide_state = &s->dev[port].port.ifs[0]; if (!ide_state->blk) { trace_handle_cmd_badport(s, port); - return -1; + return; } tbl_addr = le64_to_cpu(cmd->tbl_addr); @@ -1312,7 +1337,7 @@ static int handle_cmd(AHCIState *s, int port, uint8_t slot) DMA_DIRECTION_TO_DEVICE, MEMTXATTRS_UNSPECIFIED); if (!cmd_fis) { trace_handle_cmd_badfis(s, port); - return -1; + return; } else if (cmd_len != 0x80) { ahci_trigger_irq(s, &s->dev[port], AHCI_PORT_IRQ_BIT_HBFS); trace_handle_cmd_badmap(s, port, cmd_len); @@ -1336,15 +1361,6 @@ static int handle_cmd(AHCIState *s, int port, uint8_t slot) out: dma_memory_unmap(s->as, cmd_fis, cmd_len, DMA_DIRECTION_TO_DEVICE, cmd_len); - - if (s->dev[port].port.ifs[0].status & (BUSY_STAT|DRQ_STAT)) { - /* async command, complete later */ - s->dev[port].busy_slot = slot; - return -1; - } - - /* done handling the command */ - return 0; } /* Transfer PIO data between RAM and device */ @@ -1498,6 +1514,16 @@ static int ahci_dma_rw_buf(const IDEDMA *dma, bool is_write) return 1; } +static void ahci_clear_cmd_issue(AHCIDevice *ad, uint8_t slot) +{ + IDEState *ide_state = &ad->port.ifs[0]; + + if (!(ide_state->status & (BUSY_STAT | DRQ_STAT))) { + ad->port_regs.cmd_issue &= ~(1 << slot); + } +} + +/* Non-NCQ command is done - This function is never called for NCQ commands. */ static void ahci_cmd_done(const IDEDMA *dma) { AHCIDevice *ad = DO_UPCAST(AHCIDevice, dma, dma); @@ -1506,11 +1532,15 @@ static void ahci_cmd_done(const IDEDMA *dma) /* no longer busy */ if (ad->busy_slot != -1) { - ad->port_regs.cmd_issue &= ~(1 << ad->busy_slot); + ahci_clear_cmd_issue(ad, ad->busy_slot); ad->busy_slot = -1; } - /* update d2h status */ + /* + * In reality, for non-NCQ commands, PxCI is cleared after receiving a D2H + * FIS with the interrupt bit set, but since ahci_write_fis_d2h() will raise + * an IRQ, we need to call them in reverse order. + */ ahci_write_fis_d2h(ad, true); if (ad->port_regs.cmd_issue && !ad->check_bh) {