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Message-ID: <0b110e7f-9d08-496e-158e-8c3ff7307423@loongson.cn>
Date: Mon, 20 Apr 2020 18:32:39 +0800
From: maobibo <maobibo@...ngson.cn>
To: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>,
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 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
> 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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