linux-kernel - Re: [RFC 2/5] powerpc: kvm: drop 32-bit booke

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Message-ID: <1f1beb34-65cc-4038-a8b2-de8af3e0703e@csgroup.eu>
Date: Fri, 13 Dec 2024 07:25:01 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Arnd Bergmann <arnd@...db.de>, Arnd Bergmann <arnd@...nel.org>,
 kvm@...r.kernel.org
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 Huacai Chen <chenhuacai@...nel.org>, Jiaxun Yang <jiaxun.yang@...goat.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 Naveen N Rao <naveen@...nel.org>, Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Alexander Graf <graf@...zon.com>, Crystal Wood <crwood@...hat.com>,
 Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>, Vitaly Kuznetsov <vkuznets@...hat.com>,
 David Woodhouse <dwmw2@...radead.org>, Paul Durrant <paul@....org>,
 Marc Zyngier <maz@...nel.org>, linux-kernel@...r.kernel.org,
 linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org
Subject: Re: [RFC 2/5] powerpc: kvm: drop 32-bit booke

Le 12/12/2024 à 22:08, Arnd Bergmann a écrit :
> On Thu, Dec 12, 2024, at 19:35, Christophe Leroy wrote:
>> Le 12/12/2024 à 13:55, Arnd Bergmann a écrit :
>>> From: Arnd Bergmann <arnd@...db.de>
> 
>>>
>>> Support for 64-bit hosts remains unchanged, for both 32-bit and
>>> 64-bit guests.
>>>
> 
>>>    arch/powerpc/include/asm/kvm_book3s_32.h    |  36 --
>>>    arch/powerpc/include/asm/kvm_booke.h        |   4 -
>>>    arch/powerpc/include/asm/kvm_booke_hv_asm.h |   2 -
>>>    arch/powerpc/kvm/Kconfig                    |  22 +-
>>>    arch/powerpc/kvm/Makefile                   |  15 -
>>>    arch/powerpc/kvm/book3s_32_mmu_host.c       | 396 --------------
>>>    arch/powerpc/kvm/booke.c                    | 268 ----------
>>>    arch/powerpc/kvm/booke.h                    |   8 -
>>>    arch/powerpc/kvm/booke_emulate.c            |  44 --
>>>    arch/powerpc/kvm/booke_interrupts.S         | 535 -------------------
>>>    arch/powerpc/kvm/bookehv_interrupts.S       | 102 ----
>>>    arch/powerpc/kvm/e500.c                     | 553 --------------------
>>>    arch/powerpc/kvm/e500.h                     |  40 --
>>>    arch/powerpc/kvm/e500_emulate.c             | 100 ----
>>>    arch/powerpc/kvm/e500_mmu_host.c            |  54 --
>>>    arch/powerpc/kvm/e500mc.c                   |   5 +-
>>>    arch/powerpc/kvm/trace_booke.h              |  14 -
>>>    17 files changed, 4 insertions(+), 2194 deletions(-)
>>>    delete mode 100644 arch/powerpc/include/asm/kvm_book3s_32.h
>>>    delete mode 100644 arch/powerpc/kvm/book3s_32_mmu_host.c
>>>    delete mode 100644 arch/powerpc/kvm/booke_interrupts.S
>>>    delete mode 100644 arch/powerpc/kvm/e500.c
>>
>> Left over ?
>>
>> arch/powerpc/kernel/head_booke.h:#include <asm/kvm_asm.h>
>> arch/powerpc/kernel/head_booke.h:#include <asm/kvm_booke_hv_asm.h>
>> arch/powerpc/kernel/head_booke.h:       b
>> kvmppc_handler_\intno\()_\srr1
> 
> As far as I can tell, these are still needed for e5500/e6500,
> but you know more about the platform than I do.

$ git grep kvmppc_handler_ arch/powerpc/
arch/powerpc/kvm/bookehv_interrupts.S: 
_GLOBAL(kvmppc_handler_\intno\()_\srr1)

In your patch you remove the include of head_booke.h from there:

diff --git a/arch/powerpc/kvm/bookehv_interrupts.S 
b/arch/powerpc/kvm/bookehv_interrupts.S
index 8b4a402217ba..c75350fc449e 100644
--- a/arch/powerpc/kvm/bookehv_interrupts.S
+++ b/arch/powerpc/kvm/bookehv_interrupts.S
@@ -18,13 +18,9 @@
  #include <asm/asm-offsets.h>
  #include <asm/bitsperlong.h>

-#ifdef CONFIG_64BIT
  #include <asm/exception-64e.h>
  #include <asm/hw_irq.h>
  #include <asm/irqflags.h>
-#else
-#include "../kernel/head_booke.h" /* for THREAD_NORMSAVE() */
-#endif

  #define LONGBYTES		(BITS_PER_LONG / 8)

$ git grep head_booke.h
arch/powerpc/kernel/asm-offsets.c:#include "head_booke.h"
arch/powerpc/kernel/head_44x.S:#include "head_booke.h"
arch/powerpc/kernel/head_85xx.S:#include "head_booke.h"

$ git grep head_85xx.o
arch/powerpc/kernel/Makefile:obj-$(CONFIG_PPC_85xx)             += 
head_85xx.o

CONFIG_PPC_85xx depends on CONFIG_PPC32.

CONFIG_E5500_CPU and CONFIG_E6500_CPU both depend on CONFIG_PPC64.

So yes it is used on e5500/e6500 but only when they run a 32 bits kernel 
built with CONFIG_PPC_85xx. Isn't it what you want to get rid of with 
this patch ?

Am I missing something ?

Christophe