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From ba3bbcb7fe5b4bb2e8be8dee46cfb637333471f6 Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <>
Date: Sat, 11 Jan 2014 17:59:52 +0100
Subject: [PATCH 02/22] Revert "pc: Disable the "use flash device for BIOS unless KVM" misfeature"

RH-Author: Laszlo Ersek <>
Message-id: <>
Patchwork-id: 56614
O-Subject: [RHEL-7.0 qemu-kvm PATCH 02/18] Revert "pc: Disable the "use flash device for BIOS unless KVM" misfeature"
Bugzilla: 1032346
RH-Acked-by: Paolo Bonzini <>
RH-Acked-by: Amos Kong <>
RH-Acked-by: Andrew Jones <>
RH-Acked-by: Kevin Wolf <>

This reverts commit 23231f783d082bef74ba1d9fed6b07fdd058cb87.

RHEL-7 note -- I'll quote Markus' awesome original, RHEL-7-specific commit
message here:

> Use of a flash memory device for the BIOS was added in series "[PATCH
> v10 0/8] PC system flash support", commit 4732dca..1b89faf, v1.1.
> Flash vs. ROM is a guest-visible difference.  Thus, flash use had to
> be suppressed for machine types pc-1.0 and older.  This was
> accomplished by adding a dummy device "pc-sysfw" with property
> "rom_only":
> * Non-zero rom_only means "use ROM".  Default for pc-1.0 and older.
> * Zero rom_only means "maybe use flash".  Default for newer machines.
> Not only is the dummy device ugly, it was also retroactively added to
> the older machine types!  Fortunately, it's not guest-visible (thus no
> immediate guest ABI breakage), and has no vmstate (thus no immediate
> migration breakage).  Breakage occurs only if the user unwisely
> enables flash by setting rom_only to zero.  Patch review FAIL #1.
> Why "maybe use flash"?  Flash didn't work with KVM.  Therefore,
> rom_only=0 really means "use flash, except when KVM is enabled, use
> ROM".  This is a Bad Idea, because it makes enabling/ disabling KVM
> guest-visible.  Patch review FAIL #2.
> Aside: it also precludes migrating between KVM on and off, but that's
> not possible for other reasons anyway.
> Upstream commit 9953f88 killed the misfeature for new machine types.
> Upstream commit 9e1c2ec reverted the kill, but left a dead variable
> behind.  This is what's in RHEL-7 is before this patch.
> KVM has recently been made to support flash (KVM_CAP_READONLY_MEM),
> which permitted upstream QEMU to redo the flash vs. ROM switch
> properly (commit 338ea90..dafb82e).

This commit range is Jordan's series that this backport is all about.

> The required follow-up cleanup
> hasn't been committed, yet: Paolo's [PATCH v2 0/3] Remove legacy sysfw
> code.

It has now, I'm including it in the series.

> Instead of backporting all that, I'm simply ripping out the flash
> feature.  ROM has been working just fine for us, and I don't think we
> should complicate RHEL-7 maintenance and support by having two ways to
> map BIOS, at least not without sufficient business reason.

The business reason seems to be OVMF...

> The result behaves just like upstream with the follow-up cleanup
> applied, except -pflash doesn't affect the BIOS mapping, but remains
> as it always was: it creates an unused drive.

... and for it we need -pflash to create the real thing.

Signed-off-by: Laszlo Ersek <>
 hw/block/pc_sysfw.c | 9 ---------
 1 file changed, 9 deletions(-)

Signed-off-by: Miroslav Rezanina <>
 hw/block/pc_sysfw.c |    9 ---------
 1 files changed, 0 insertions(+), 9 deletions(-)

diff --git a/hw/block/pc_sysfw.c b/hw/block/pc_sysfw.c
index 0bc5b7a..6149b20 100644
--- a/hw/block/pc_sysfw.c
+++ b/hw/block/pc_sysfw.c
@@ -36,7 +36,6 @@
 #define BIOS_FILENAME "bios.bin"
-#if 0   /* Disabled for Red Hat Enterprise Linux */
 typedef struct PcSysFwDevice {
     SysBusDevice busdev;
     uint8_t rom_only;
@@ -136,7 +135,6 @@ static void pc_system_flash_init(MemoryRegion *rom_memory,
     pc_isa_bios_init(rom_memory, flash_mem, size);
-#endif  /* Disabled for Red Hat Enterprise Linux */
 static void old_pc_system_rom_init(MemoryRegion *rom_memory)
@@ -193,7 +191,6 @@ static void old_pc_system_rom_init(MemoryRegion *rom_memory)
-#if 0   /* Disabled for Red Hat Enterprise Linux */
  * Bug-compatible flash vs. ROM selection enabled?
  * A few older machines enable this.
@@ -288,9 +285,3 @@ static void pcsysfw_register (void)
 type_init (pcsysfw_register);
-#else   /* Disabled for Red Hat Enterprise Linux */
-void pc_system_firmware_init(MemoryRegion *rom_memory)
-    old_pc_system_rom_init(rom_memory);