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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.gmail.com with ESMTPSA id j11sm2938709ejt.114.2021.11.04.11.53.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Nov 2021 11:53:54 -0700 (PDT) Message-ID: <0154963b-6bb5-fc33-6a29-bfa57f187c38@redhat.com> Date: Thu, 4 Nov 2021 19:50:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [RFC][PATCH 18/22] x86,kvm: Remove .fixup usage Content-Language: en-US To: Peter Zijlstra , x86@kernel.org Cc: linux-kernel@vger.kernel.org, jpoimboe@redhat.com, mark.rutland@arm.com, dvyukov@google.com, seanjc@google.com, mbenes@suse.cz References: <20211104164729.226550532@infradead.org> <20211104165525.588957687@infradead.org> From: Paolo Bonzini In-Reply-To: <20211104165525.588957687@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/4/21 17:47, Peter Zijlstra wrote: > KVM instruction emulation has a gnarly hack where the .fixup does a > return, luckily exceptions can easily emulate a return so create a new > extable type to fully do the FASTOP magic. > > Signed-off-by: Peter Zijlstra (Intel) > --- > arch/x86/include/asm/extable_fixup_types.h | 1 + > arch/x86/kvm/emulate.c | 14 +++----------- > arch/x86/mm/extable.c | 11 +++++++++++ > 3 files changed, 15 insertions(+), 11 deletions(-) > > --- a/arch/x86/include/asm/extable_fixup_types.h > +++ b/arch/x86/include/asm/extable_fixup_types.h > @@ -40,5 +40,6 @@ > #define EX_TYPE_ONE_REG (EX_TYPE_IMM_REG | EX_TYPE_IMM(1)) > > #define EX_TYPE_FAULT_SGX 18 > +#define EX_TYPE_KVM_FASTOP 19 > > #endif > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -344,7 +344,7 @@ static int fastop(struct x86_emulate_ctx > __FOP_RET(#op "_" #dst) > > #define FOP1EEX(op, dst) \ > - FOP1E(op, dst) _ASM_EXTABLE(10b, kvm_fastop_exception) > + FOP1E(op, dst) _ASM_EXTABLE_TYPE(10b, 10b, EX_TYPE_KVM_FASTOP) There's a ret right after the 10b label, so I think you can just use this: diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 493511efa3dc..f382c03c5954 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -315,7 +315,7 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop); __FOP_FUNC(#name) #define __FOP_RET(name) \ - "ret \n\t" \ + "11: ret \n\t" \ ".size " name ", .-" name "\n\t" #define FOP_RET(name) \ @@ -344,7 +344,7 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop); __FOP_RET(#op "_" #dst) #define FOP1EEX(op, dst) \ - FOP1E(op, dst) _ASM_EXTABLE(10b, kvm_fastop_exception) + FOP1E(op, dst) _ASM_EXTABLE_TYPE_REG(10b, 11b, EX_TYPE_ZERO_REG, %esi) #define FASTOP1(op) \ FOP_START(op) \ Paolo