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From ba3bbcb7fe5b4bb2e8be8dee46cfb637333471f6 Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Sat, 11 Jan 2014 17:59:52 +0100
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Subject: [PATCH 02/22] Revert "pc: Disable the "use flash device for BIOS unless KVM" misfeature"
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RH-Author: Laszlo Ersek <lersek@redhat.com>
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Message-id: <1389463208-6278-3-git-send-email-lersek@redhat.com>
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Patchwork-id: 56614
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O-Subject: [RHEL-7.0 qemu-kvm PATCH 02/18] Revert "pc: Disable the "use flash device for BIOS unless KVM" misfeature"
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Bugzilla: 1032346
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Amos Kong <akong@redhat.com>
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RH-Acked-by: Andrew Jones <drjones@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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This reverts commit 23231f783d082bef74ba1d9fed6b07fdd058cb87.
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RHEL-7 note -- I'll quote Markus' awesome original, RHEL-7-specific commit
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message here:
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> Use of a flash memory device for the BIOS was added in series "[PATCH
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> v10 0/8] PC system flash support", commit 4732dca..1b89faf, v1.1.
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>
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> Flash vs. ROM is a guest-visible difference.  Thus, flash use had to
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> be suppressed for machine types pc-1.0 and older.  This was
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> accomplished by adding a dummy device "pc-sysfw" with property
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> "rom_only":
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>
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> * Non-zero rom_only means "use ROM".  Default for pc-1.0 and older.
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> * Zero rom_only means "maybe use flash".  Default for newer machines.
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>
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> Not only is the dummy device ugly, it was also retroactively added to
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> the older machine types!  Fortunately, it's not guest-visible (thus no
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> immediate guest ABI breakage), and has no vmstate (thus no immediate
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> migration breakage).  Breakage occurs only if the user unwisely
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> enables flash by setting rom_only to zero.  Patch review FAIL #1.
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>
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> Why "maybe use flash"?  Flash didn't work with KVM.  Therefore,
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> rom_only=0 really means "use flash, except when KVM is enabled, use
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> ROM".  This is a Bad Idea, because it makes enabling/ disabling KVM
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> guest-visible.  Patch review FAIL #2.
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>
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> Aside: it also precludes migrating between KVM on and off, but that's
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> not possible for other reasons anyway.
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>
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> Upstream commit 9953f88 killed the misfeature for new machine types.
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> Upstream commit 9e1c2ec reverted the kill, but left a dead variable
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> behind.  This is what's in RHEL-7 is before this patch.
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>
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> KVM has recently been made to support flash (KVM_CAP_READONLY_MEM),
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> which permitted upstream QEMU to redo the flash vs. ROM switch
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> properly (commit 338ea90..dafb82e).
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This commit range is Jordan's series that this backport is all about.
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> The required follow-up cleanup
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> hasn't been committed, yet: Paolo's [PATCH v2 0/3] Remove legacy sysfw
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> code.
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It has now, I'm including it in the series.
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> Instead of backporting all that, I'm simply ripping out the flash
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> feature.  ROM has been working just fine for us, and I don't think we
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> should complicate RHEL-7 maintenance and support by having two ways to
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> map BIOS, at least not without sufficient business reason.
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The business reason seems to be OVMF...
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> The result behaves just like upstream with the follow-up cleanup
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> applied, except -pflash doesn't affect the BIOS mapping, but remains
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> as it always was: it creates an unused drive.
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... and for it we need -pflash to create the real thing.
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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---
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 hw/block/pc_sysfw.c | 9 ---------
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 1 file changed, 9 deletions(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/block/pc_sysfw.c |    9 ---------
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 1 files changed, 0 insertions(+), 9 deletions(-)
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diff --git a/hw/block/pc_sysfw.c b/hw/block/pc_sysfw.c
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index 0bc5b7a..6149b20 100644
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--- a/hw/block/pc_sysfw.c
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+++ b/hw/block/pc_sysfw.c
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@@ -36,7 +36,6 @@
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 #define BIOS_FILENAME "bios.bin"
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-#if 0   /* Disabled for Red Hat Enterprise Linux */
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 typedef struct PcSysFwDevice {
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     SysBusDevice busdev;
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     uint8_t rom_only;
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@@ -136,7 +135,6 @@ static void pc_system_flash_init(MemoryRegion *rom_memory,
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     pc_isa_bios_init(rom_memory, flash_mem, size);
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 }
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-#endif  /* Disabled for Red Hat Enterprise Linux */
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 static void old_pc_system_rom_init(MemoryRegion *rom_memory)
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 {
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@@ -193,7 +191,6 @@ static void old_pc_system_rom_init(MemoryRegion *rom_memory)
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                                 bios);
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 }
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-#if 0   /* Disabled for Red Hat Enterprise Linux */
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 /*
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  * Bug-compatible flash vs. ROM selection enabled?
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  * A few older machines enable this.
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@@ -288,9 +285,3 @@ static void pcsysfw_register (void)
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 type_init (pcsysfw_register);
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-#else   /* Disabled for Red Hat Enterprise Linux */
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-void pc_system_firmware_init(MemoryRegion *rom_memory)
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-{
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-    old_pc_system_rom_init(rom_memory);
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-}
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-#endif
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-- 
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1.7.1
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