From: John Snow Date: Fri, 8 Jun 2018 17:17:36 +0000 (-0400) Subject: ahci: fix PxCI register race X-Git-Tag: qemu-xen-4.12.0-rc1~179^2~28 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=5694c7eacce6b263ad7497cc1bb76aad746cfd4e;p=qemu-xen.git ahci: fix PxCI register race Fixes: https://bugs.launchpad.net/qemu/+bug/1769189 AHCI presently signals completion prior to the PxCI register being cleared to indicate completion. If a guest driver attempts to issue a new command in its IRQ handler, it might be surprised to learn there is still a command pending. In the case of Windows 10's boot driver, it will actually poll the IRQ register hoping to find out when the command is done running -- which will never happen, as there isn't a command running. Fix this: clear PxCI in ahci_cmd_done and not in the asynchronous BH. Because it now runs synchronously, we don't need to check if the command is actually done by spying on the ATA registers. We know it's done. CC: qemu-stable Reported-by: François Guerraz Tested-by: Bruce Rogers Signed-off-by: John Snow Reviewed-by: Stefan Hajnoczi Reviewed-by: Jeff Cody Message-id: 20180531004323.4611-3-jsnow@redhat.com Signed-off-by: John Snow --- diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c index 66f55aecb3..b11640ddbb 100644 --- a/hw/ide/ahci.c +++ b/hw/ide/ahci.c @@ -532,13 +532,6 @@ static void ahci_check_cmd_bh(void *opaque) qemu_bh_delete(ad->check_bh); ad->check_bh = NULL; - if ((ad->busy_slot != -1) && - !(ad->port.ifs[0].status & (BUSY_STAT|DRQ_STAT))) { - /* no longer busy */ - ad->port_regs.cmd_issue &= ~(1 << ad->busy_slot); - ad->busy_slot = -1; - } - check_cmd(ad->hba, ad->port_no); } @@ -1425,6 +1418,12 @@ static void ahci_cmd_done(IDEDMA *dma) trace_ahci_cmd_done(ad->hba, ad->port_no); + /* no longer busy */ + if (ad->busy_slot != -1) { + ad->port_regs.cmd_issue &= ~(1 << ad->busy_slot); + ad->busy_slot = -1; + } + /* update d2h status */ ahci_write_fis_d2h(ad);