From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56699) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alK1o-0007kF-8m for qemu-devel@nongnu.org; Wed, 30 Mar 2016 13:35:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1alK1j-0003mb-JU for qemu-devel@nongnu.org; Wed, 30 Mar 2016 13:35:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58886) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alK1j-0003mC-AU for qemu-devel@nongnu.org; Wed, 30 Mar 2016 13:35:31 -0400 References: <1458728792-15779-1-git-send-email-den@openvz.org> <1458728792-15779-2-git-send-email-den@openvz.org> From: John Snow Message-ID: <56FC0E61.1080709@redhat.com> Date: Wed, 30 Mar 2016 13:35:29 -0400 MIME-Version: 1.0 In-Reply-To: <1458728792-15779-2-git-send-email-den@openvz.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/3] ide: don't loose pending dma state List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Denis V. Lunev" , qemu-devel@nongnu.org Cc: Pavel Butsykin On 03/23/2016 06:26 AM, Denis V. Lunev wrote: > From: Pavel Butsykin > > If the migration occurs after the IDE DMA has been set up but before it > has been initiated, the state gets lost upon save/restore. Specifically, > ->dma_cb callback gets cleared, so, when the guest eventually starts bus > mastering, the DMA never completes, causing the guest to time out the > operation. > > OTOH all the infrastructure is already in place to restart the DMA if > the migration happens while the DMA is in progress. > > So reuse that infrastructure, by calling the DMA callback with an > artificial error code in pre_save if the callback is already set but > DMAING is clear. The callback then sets bus->error_status to indicate > the need for restart; however since DMAING is clear the state upon > restore will be exactly "ready forDMA" as before the save. > > This patch only fixes the IDE DMA case; the ATAPI DMA is left with a stub > for now since its restart hadn't been implemented yet. It will be > addressed in the followup patch. > > Signed-off-by: Pavel Butsykin > Reviewed-by: Roman Kagan > Signed-off-by: Denis V. Lunev > CC: John Snow > --- > hw/ide/atapi.c | 9 ++++++++- > hw/ide/core.c | 9 ++++++++- > hw/ide/internal.h | 7 +++++++ > hw/ide/pci.c | 3 +++ > 4 files changed, 26 insertions(+), 2 deletions(-) > > diff --git a/hw/ide/atapi.c b/hw/ide/atapi.c > index 1fe58ab..268220d 100644 > --- a/hw/ide/atapi.c > +++ b/hw/ide/atapi.c > @@ -381,7 +381,14 @@ static void ide_atapi_cmd_read_dma_cb(void *opaque, int ret) > IDEState *s = opaque; > int data_offset, n; > > - if (ret < 0) { > + if (ret < 0) { /* XXX: handle -ESTATESAVE for migration */ > + if (ret == -ESTATESAVE) { > + /* > + * This case is not really an error > + * but a request to save the state. > + */ > + return; > + } > ide_atapi_io_error(s, ret); > goto eot; > } > diff --git a/hw/ide/core.c b/hw/ide/core.c > index 241e840..872e11f 100644 > --- a/hw/ide/core.c > +++ b/hw/ide/core.c > @@ -810,7 +810,14 @@ static void ide_dma_cb(void *opaque, int ret) > else if (s->dma_cmd == IDE_DMA_TRIM) > op |= IDE_RETRY_TRIM; > > - if (ide_handle_rw_error(s, -ret, op)) { > + if (ret == -ESTATESAVE) { > + /* > + * This case is not really an error > + * but a request to save the state. > + */ > + s->bus->error_status = op; > + return; > + } else if (ide_handle_rw_error(s, -ret, op)) { > return; > } > } > diff --git a/hw/ide/internal.h b/hw/ide/internal.h > index 86bde26..dcd8627 100644 > --- a/hw/ide/internal.h > +++ b/hw/ide/internal.h > @@ -513,6 +513,13 @@ struct IDEDevice { > #define IDE_RETRY_TRIM 0x80 > #define IDE_RETRY_HBA 0x100 > > +/* > + * a code to trigger entering error path and save/restore the "ready to DMA" > + * state just like DMA-ing state. (Ab)use EINPROGRESS as it's not supposed to > + * come from the block layer > + */ > +#define ESTATESAVE EINPROGRESS > + > static inline IDEState *idebus_active_if(IDEBus *bus) > { > return bus->ifs + bus->unit; > diff --git a/hw/ide/pci.c b/hw/ide/pci.c > index 92ffee7..e1f89fa 100644 > --- a/hw/ide/pci.c > +++ b/hw/ide/pci.c > @@ -308,6 +308,9 @@ static void ide_bmdma_pre_save(void *opaque) > BMDMAState *bm = opaque; > uint8_t abused_bits = BM_MIGRATION_COMPAT_STATUS_BITS; > > + if (!(bm->status & BM_STATUS_DMAING) && bm->dma_cb) { > + bm->dma_cb(bmdma_active_if(bm), -ESTATESAVE); > + } > bm->migration_retry_unit = bm->bus->retry_unit; > bm->migration_retry_sector_num = bm->bus->retry_sector_num; > bm->migration_retry_nsector = bm->bus->retry_nsector; > Reviewed-by: John Snow