From 50613448205a2e85e90a488be1c83d0f2b5f2d52 Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Fri, 26 Jun 2015 16:19:47 +0200 Subject: Migration compat for fdc Patchwork-id: 66534 O-Subject: [RHEL-7.2 qemu-kvm-rhev PATCH 1/1] Migration compat for fdc Bugzilla: 1215091 RH-Acked-by: Amit Shah RH-Acked-by: Paolo Bonzini RH-Acked-by: Juan Quintela From: "Dr. David Alan Gilbert" 2.2 added some sections into the fdc and floppy drive, this patch disables those new sections for reverse migration compatibility. There are three pieces of data added to the migration: 1) 'perpendicular mode' on the drive - i.e. 2.88MB mode, that was rare as hens teeth and the flag isn't actually used anywhere. 2) fdc_reset_sensei This relates to the state of the fdc just after a reset command; the fdc produces four 'sense' states internally (corresponding to one external interrupt) that is there for backwards compatibility to an older fdc (and to 8" drives!!). This compatibility code was added to qemu to fix SCO Openserver floppy problems, ~2009. Migration just after an fdc-reset would get the initial interrupt but lose the extra 3 sense states. Print a log message since that's guest visible, but it's not knowingly caused us a problem so don't fail migration. 3) result-timer The emulation models a delay after the 'read id' command which is handled by a timer; if we migrate before the timer goes off we probably wont complete the command. I'm worried that the most likely time that a 'read id' would be used would be in a background probe to see if there's a floppy present, so again, don't fail the migrate, but do print a log message. With any luck any sane floppy driver will have a timeout; if we hit problems then a work around would be to make the pre-save mark the command as finished with error. Signed-off-by: Dr. David Alan Gilbert Signed-off-by: Miroslav Rezanina (cherry picked from commit b18d89c56aa26e86fb6194f77a15a72244d5ff88) --- hw/block/fdc.c | 39 +++++++++++++++++++++++++++++++++++++-- 1 file changed, 37 insertions(+), 2 deletions(-) diff --git a/hw/block/fdc.c b/hw/block/fdc.c index 90cd9a0..d3213cb 100644 --- a/hw/block/fdc.c +++ b/hw/block/fdc.c @@ -36,6 +36,7 @@ #include "hw/isa/isa.h" #include "hw/sysbus.h" #include "hw/block/block.h" +#include "migration/migration.h" #include "sysemu/block-backend.h" #include "sysemu/blockdev.h" #include "sysemu/sysemu.h" @@ -1042,6 +1043,10 @@ static bool fdrive_perpendicular_needed(void *opaque) { FDrive *drive = opaque; + if (migrate_pre_2_2) { + return false; + } + return drive->perpendicular != 0; } @@ -1134,8 +1139,20 @@ static int fdc_post_load(void *opaque, int version_id) static bool fdc_reset_sensei_needed(void *opaque) { FDCtrl *s = opaque; + bool needed = s->reset_sensei != 0; + + if (migrate_pre_2_2) { + /* + * This probably wont matter for most OSs, but it's good to log + * it just incase we find it causes problems. + */ + if (needed) { + error_report("INFO: fdc migration just after reset (sensei!=0)"); + } + return false; + } - return s->reset_sensei != 0; + return needed; } static const VMStateDescription vmstate_fdc_reset_sensei = { @@ -1152,8 +1169,26 @@ static const VMStateDescription vmstate_fdc_reset_sensei = { static bool fdc_result_timer_needed(void *opaque) { FDCtrl *s = opaque; + bool needed = timer_pending(s->result_timer); + + if (migrate_pre_2_2) { + /* + * This could upset some OSs if their read-id command doesn't + * complete, so lets log something. + */ + if (needed) { + error_report("INFO: fdc migration just after read-id (timer!=0)"); + } + /* + * However, since it's not apparently caused us problems for many + * years, don't fail the migration, especially as this could + * happen as part of a background drive-probe which if it fails + * won't be a problem. + */ + return false; + } - return timer_pending(s->result_timer); + return needed; } static const VMStateDescription vmstate_fdc_result_timer = { -- 1.8.3.1