mbox series

[v2,0/4] Remove 32-bit Xen PV guest support

Message ID 20200701110650.16172-1-jgross@suse.com (mailing list archive)
Headers show
Series Remove 32-bit Xen PV guest support | expand

Message

Jürgen Groß July 1, 2020, 11:06 a.m. UTC 
The long term plan has been to replace Xen PV guests by PVH. The first
victim of that plan are now 32-bit PV guests, as those are used only
rather seldom these days. Xen on x86 requires 64-bit support and with
Grub2 now supporting PVH officially since version 2.04 there is no
need to keep 32-bit PV guest support alive in the Linux kernel.
Additionally Meltdown mitigation is not available in the kernel running
as 32-bit PV guest, so dropping this mode makes sense from security
point of view, too.

Changes in V2:
- rebase to 5.8 kernel
- addressed comments to V1
- new patches 3 and 4

Juergen Gross (4):
  x86/xen: remove 32-bit Xen PV guest support
  x86/paravirt: remove 32-bit support from PARAVIRT_XXL
  x86/paravirt: cleanup paravirt macros
  x86/paravirt: use CONFIG_PARAVIRT_XXL instead of CONFIG_PARAVIRT

 arch/x86/entry/entry_32.S                   | 109 +------
 arch/x86/entry/entry_64.S                   |   4 +-
 arch/x86/entry/vdso/vdso32/vclock_gettime.c |   1 +
 arch/x86/include/asm/fixmap.h               |   2 +-
 arch/x86/include/asm/paravirt.h             | 107 +-----
 arch/x86/include/asm/paravirt_types.h       |  21 --
 arch/x86/include/asm/pgtable-3level_types.h |   5 -
 arch/x86/include/asm/proto.h                |   2 +-
 arch/x86/include/asm/required-features.h    |   2 +-
 arch/x86/include/asm/segment.h              |   6 +-
 arch/x86/kernel/cpu/common.c                |   8 -
 arch/x86/kernel/head_32.S                   |  31 --
 arch/x86/kernel/kprobes/core.c              |   1 -
 arch/x86/kernel/kprobes/opt.c               |   1 -
 arch/x86/kernel/paravirt.c                  |  18 --
 arch/x86/kernel/paravirt_patch.c            |  17 -
 arch/x86/xen/Kconfig                        |   3 +-
 arch/x86/xen/Makefile                       |   3 +-
 arch/x86/xen/apic.c                         |  17 -
 arch/x86/xen/enlighten_pv.c                 |  52 +--
 arch/x86/xen/mmu_pv.c                       | 340 +++-----------------
 arch/x86/xen/p2m.c                          |   6 +-
 arch/x86/xen/setup.c                        |  35 +-
 arch/x86/xen/smp_pv.c                       |  18 --
 arch/x86/xen/xen-asm.S                      | 182 ++++++++++-
 arch/x86/xen/xen-asm_32.S                   | 185 -----------
 arch/x86/xen/xen-asm_64.S                   | 181 -----------
 arch/x86/xen/xen-head.S                     |   6 -
 drivers/xen/Kconfig                         |   4 +-
 29 files changed, 232 insertions(+), 1135 deletions(-)
 delete mode 100644 arch/x86/xen/xen-asm_32.S
 delete mode 100644 arch/x86/xen/xen-asm_64.S

Comments

Peter Zijlstra July 2, 2020, 8:18 a.m. UTC | #1 
On Wed, Jul 01, 2020 at 01:06:46PM +0200, Juergen Gross wrote:
> The long term plan has been to replace Xen PV guests by PVH. The first
> victim of that plan are now 32-bit PV guests, as those are used only
> rather seldom these days. Xen on x86 requires 64-bit support and with
> Grub2 now supporting PVH officially since version 2.04 there is no
> need to keep 32-bit PV guest support alive in the Linux kernel.
> Additionally Meltdown mitigation is not available in the kernel running
> as 32-bit PV guest, so dropping this mode makes sense from security
> point of view, too.

Hooray!!! Much thanks!
Brian Gerst July 2, 2020, 2:48 p.m. UTC | #2 
On Wed, Jul 1, 2020 at 7:07 AM Juergen Gross <jgross@suse.com> wrote:
>
> The long term plan has been to replace Xen PV guests by PVH. The first
> victim of that plan are now 32-bit PV guests, as those are used only
> rather seldom these days. Xen on x86 requires 64-bit support and with
> Grub2 now supporting PVH officially since version 2.04 there is no
> need to keep 32-bit PV guest support alive in the Linux kernel.
> Additionally Meltdown mitigation is not available in the kernel running
> as 32-bit PV guest, so dropping this mode makes sense from security
> point of view, too.

One thing that you missed is removing VDSO_NOTE_NONEGSEG_BIT from
vdso32/note.S.  With that removed there is no difference from the
64-bit version.

Otherwise this series looks good to me.
--
Brian Gerst
Jürgen Groß July 2, 2020, 3:45 p.m. UTC | #3 
On 02.07.20 16:48, Brian Gerst wrote:
> On Wed, Jul 1, 2020 at 7:07 AM Juergen Gross <jgross@suse.com> wrote:
>>
>> The long term plan has been to replace Xen PV guests by PVH. The first
>> victim of that plan are now 32-bit PV guests, as those are used only
>> rather seldom these days. Xen on x86 requires 64-bit support and with
>> Grub2 now supporting PVH officially since version 2.04 there is no
>> need to keep 32-bit PV guest support alive in the Linux kernel.
>> Additionally Meltdown mitigation is not available in the kernel running
>> as 32-bit PV guest, so dropping this mode makes sense from security
>> point of view, too.
> 
> One thing that you missed is removing VDSO_NOTE_NONEGSEG_BIT from
> vdso32/note.S.  With that removed there is no difference from the
> 64-bit version.

Oh, this means we can probably remove arch/x86/xen/vdso.h completely.

> 
> Otherwise this series looks good to me.

Thanks,


Juergen