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Message-ID: <793b2b58-a199-c067-aec7-b07c444a6091@linux.alibaba.com>
Date: Mon, 20 Apr 2020 18:42:15 +0800
From: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
To: maobibo <maobibo@...ngson.cn>, pbonzini@...hat.com,
tsbogend@...ha.franken.de, paulus@...abs.org, mpe@...erman.id.au,
benh@...nel.crashing.org, borntraeger@...ibm.com,
frankja@...ux.ibm.com, david@...hat.com, cohuck@...hat.com,
heiko.carstens@...ibm.com, gor@...ux.ibm.com,
sean.j.christopherson@...el.com, vkuznets@...hat.com,
wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
hpa@...or.com, maz@...nel.org, james.morse@....com,
julien.thierry.kdev@...il.com, suzuki.poulose@....com,
christoffer.dall@....com, peterx@...hat.com, thuth@...hat.com
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.cs.columbia.edu, linux-mips@...r.kernel.org,
kvm-ppc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] KVM: MIPS: clean up redundant kvm_run parameters in
assembly
On 2020/4/20 18:32, maobibo wrote:
>
>
> On 04/19/2020 03:51 PM, Tianjia Zhang wrote:
>> In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
>> structure. Earlier than historical reasons, many kvm-related function
>> parameters retain the 'kvm_run' and 'kvm_vcpu' parameters at the same time.
>> This patch does a unified cleanup of these remaining redundant parameters.
>>
>> Signed-off-by: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
>> ---
>> arch/mips/include/asm/kvm_host.h | 4 ++--
>> arch/mips/kvm/entry.c | 15 +++++----------
>> arch/mips/kvm/mips.c | 3 ++-
>> arch/mips/kvm/trap_emul.c | 2 +-
>> arch/mips/kvm/vz.c | 2 +-
>> 5 files changed, 11 insertions(+), 15 deletions(-)
>>
>> diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
>> index 971439297cea..db915c55166d 100644
>> --- a/arch/mips/include/asm/kvm_host.h
>> +++ b/arch/mips/include/asm/kvm_host.h
>> @@ -310,7 +310,7 @@ struct kvm_mmu_memory_cache {
>> #define KVM_MIPS_GUEST_TLB_SIZE 64
>> struct kvm_vcpu_arch {
>> void *guest_ebase;
>> - int (*vcpu_run)(struct kvm_run *run, struct kvm_vcpu *vcpu);
>> + int (*vcpu_run)(struct kvm_vcpu *vcpu);
>>
>> /* Host registers preserved across guest mode execution */
>> unsigned long host_stack;
>> @@ -821,7 +821,7 @@ int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks);
>> /* Debug: dump vcpu state */
>> int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu);
>>
>> -extern int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu);
>> +extern int kvm_mips_handle_exit(struct kvm_vcpu *vcpu);
>>
>> /* Building of entry/exception code */
>> int kvm_mips_entry_setup(void);
>> diff --git a/arch/mips/kvm/entry.c b/arch/mips/kvm/entry.c
>> index 16e1c93b484f..e3f29af3b6cd 100644
>> --- a/arch/mips/kvm/entry.c
>> +++ b/arch/mips/kvm/entry.c
>> @@ -204,7 +204,7 @@ static inline void build_set_exc_base(u32 **p, unsigned int reg)
>> * Assemble the start of the vcpu_run function to run a guest VCPU. The function
>> * conforms to the following prototype:
>> *
>> - * int vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu);
>> + * int vcpu_run(struct kvm_vcpu *vcpu);
>> *
>> * The exit from the guest and return to the caller is handled by the code
>> * generated by kvm_mips_build_ret_to_host().
>> @@ -217,8 +217,7 @@ void *kvm_mips_build_vcpu_run(void *addr)
>> unsigned int i;
>>
>> /*
>> - * A0: run
>> - * A1: vcpu
>> + * A0: vcpu
>> */
>>
>> /* k0/k1 not being used in host kernel context */
>> @@ -237,10 +236,10 @@ void *kvm_mips_build_vcpu_run(void *addr)
>> kvm_mips_build_save_scratch(&p, V1, K1);
>>
>> /* VCPU scratch register has pointer to vcpu */
>> - UASM_i_MTC0(&p, A1, scratch_vcpu[0], scratch_vcpu[1]);
>> + UASM_i_MTC0(&p, A0, scratch_vcpu[0], scratch_vcpu[1]);
>>
>> /* Offset into vcpu->arch */
>> - UASM_i_ADDIU(&p, K1, A1, offsetof(struct kvm_vcpu, arch));
>> + UASM_i_ADDIU(&p, K1, A0, offsetof(struct kvm_vcpu, arch));
>>
>> /*
>> * Save the host stack to VCPU, used for exception processing
>> @@ -628,10 +627,7 @@ void *kvm_mips_build_exit(void *addr)
>> /* Now that context has been saved, we can use other registers */
>>
>> /* Restore vcpu */
>> - UASM_i_MFC0(&p, S1, scratch_vcpu[0], scratch_vcpu[1]);
>> -
>> - /* Restore run (vcpu->run) */
>> - UASM_i_LW(&p, S0, offsetof(struct kvm_vcpu, run), S1);
>> + UASM_i_MFC0(&p, S0, scratch_vcpu[0], scratch_vcpu[1]);
>>
>> /*
>> * Save Host level EPC, BadVaddr and Cause to VCPU, useful to process
>> @@ -793,7 +789,6 @@ void *kvm_mips_build_exit(void *addr)
>> * with this in the kernel
>> */
>> uasm_i_move(&p, A0, S0);
>> - uasm_i_move(&p, A1, S1);
>> UASM_i_LA(&p, T9, (unsigned long)kvm_mips_handle_exit);
>> uasm_i_jalr(&p, RA, T9);
>> UASM_i_ADDIU(&p, SP, SP, -CALLFRAME_SIZ);
>
> I suggest keeping asm code untouched, the change for c code is much easier to understand, however I do not see obvious advantage to remove one redundant function parameter :)
>
>
> regards
> bibo,mao
>
This is acceptable, asm code is an independent patch, is to provide
convenience for this operation.
>
>> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
>> index 9710477a9827..32850470c037 100644
>> --- a/arch/mips/kvm/mips.c
>> +++ b/arch/mips/kvm/mips.c
>> @@ -1186,8 +1186,9 @@ static void kvm_mips_set_c0_status(void)
>> /*
>> * Return value is in the form (errcode<<2 | RESUME_FLAG_HOST | RESUME_FLAG_NV)
>> */
>> -int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
>> +int kvm_mips_handle_exit(struct kvm_vcpu *vcpu)
>> {
>> + struct kvm_run *run = vcpu->run;
>> u32 cause = vcpu->arch.host_cp0_cause;
>> u32 exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
>> u32 __user *opc = (u32 __user *) vcpu->arch.pc;
>> diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
>> index d822f3aee3dc..04c864cc356a 100644
>> --- a/arch/mips/kvm/trap_emul.c
>> +++ b/arch/mips/kvm/trap_emul.c
>> @@ -1238,7 +1238,7 @@ static int kvm_trap_emul_vcpu_run(struct kvm_vcpu *vcpu)
>> */
>> kvm_mips_suspend_mm(cpu);
>>
>> - r = vcpu->arch.vcpu_run(vcpu->run, vcpu);
>> + r = vcpu->arch.vcpu_run(vcpu);
>>
>> /* We may have migrated while handling guest exits */
>> cpu = smp_processor_id();
>> diff --git a/arch/mips/kvm/vz.c b/arch/mips/kvm/vz.c
>> index 94f1d23828e3..c5878fa0636d 100644
>> --- a/arch/mips/kvm/vz.c
>> +++ b/arch/mips/kvm/vz.c
>> @@ -3152,7 +3152,7 @@ static int kvm_vz_vcpu_run(struct kvm_vcpu *vcpu)
>> kvm_vz_vcpu_load_tlb(vcpu, cpu);
>> kvm_vz_vcpu_load_wired(vcpu);
>>
>> - r = vcpu->arch.vcpu_run(vcpu->run, vcpu);
>> + r = vcpu->arch.vcpu_run(vcpu);
>>
>> kvm_vz_vcpu_save_wired(vcpu);
>>
>>
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