Re: [PATCH v6 1/5] KVM: s390: clean up redundant 'kvm_run' parameters

Re: [PATCH v6 1/5] KVM: s390: clean up redundant 'kvm_run' parameters

[Christian Borntraeger]

On 23.06.20 15:14, Tianjia Zhang wrote:
> In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
> structure. For 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@linux.alibaba.com>
> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/s390/kvm/kvm-s390.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)

Tinajia,

I have trouble seeing value in this particular patch. We add LOCs
without providing any noticable benefit. All other patches in this series at
least reduce the amount of code. So I would defer this to Paolo if he prefers
to have this way across all architectures. 
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index d47c19718615..f5f96dc33712 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4175,8 +4175,9 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
>  	return rc;
>  }
>  
> -static void sync_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> +static void sync_regs_fmt2(struct kvm_vcpu *vcpu)
>  {
> +	struct kvm_run *kvm_run = vcpu->run;
>  	struct runtime_instr_cb *riccb;
>  	struct gs_cb *gscb;
>  
> @@ -4242,8 +4243,10 @@ static void sync_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  	/* SIE will load etoken directly from SDNX and therefore kvm_run */
>  }
>  
> -static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> +static void sync_regs(struct kvm_vcpu *vcpu)
>  {
> +	struct kvm_run *kvm_run = vcpu->run;
> +
>  	if (kvm_run->kvm_dirty_regs & KVM_SYNC_PREFIX)
>  		kvm_s390_set_prefix(vcpu, kvm_run->s.regs.prefix);
>  	if (kvm_run->kvm_dirty_regs & KVM_SYNC_CRS) {
> @@ -4272,7 +4275,7 @@ static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  
>  	/* Sync fmt2 only data */
>  	if (likely(!kvm_s390_pv_cpu_is_protected(vcpu))) {
> -		sync_regs_fmt2(vcpu, kvm_run);
> +		sync_regs_fmt2(vcpu);
>  	} else {
>  		/*
>  		 * In several places we have to modify our internal view to
> @@ -4291,8 +4294,10 @@ static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  	kvm_run->kvm_dirty_regs = 0;
>  }
>  
> -static void store_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> +static void store_regs_fmt2(struct kvm_vcpu *vcpu)
>  {
> +	struct kvm_run *kvm_run = vcpu->run;
> +
>  	kvm_run->s.regs.todpr = vcpu->arch.sie_block->todpr;
>  	kvm_run->s.regs.pp = vcpu->arch.sie_block->pp;
>  	kvm_run->s.regs.gbea = vcpu->arch.sie_block->gbea;
> @@ -4312,8 +4317,10 @@ static void store_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  	/* SIE will save etoken directly into SDNX and therefore kvm_run */
>  }
>  
> -static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> +static void store_regs(struct kvm_vcpu *vcpu)
>  {
> +	struct kvm_run *kvm_run = vcpu->run;
> +
>  	kvm_run->psw_mask = vcpu->arch.sie_block->gpsw.mask;
>  	kvm_run->psw_addr = vcpu->arch.sie_block->gpsw.addr;
>  	kvm_run->s.regs.prefix = kvm_s390_get_prefix(vcpu);
> @@ -4332,7 +4339,7 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  	current->thread.fpu.fpc = vcpu->arch.host_fpregs.fpc;
>  	current->thread.fpu.regs = vcpu->arch.host_fpregs.regs;
>  	if (likely(!kvm_s390_pv_cpu_is_protected(vcpu)))
> -		store_regs_fmt2(vcpu, kvm_run);
> +		store_regs_fmt2(vcpu);
>  }
>  
>  int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> @@ -4370,7 +4377,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>  		goto out;
>  	}
>  
> -	sync_regs(vcpu, kvm_run);
> +	sync_regs(vcpu);
>  	enable_cpu_timer_accounting(vcpu);
>  
>  	might_fault();
> @@ -4392,7 +4399,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>  	}
>  
>  	disable_cpu_timer_accounting(vcpu);
> -	store_regs(vcpu, kvm_run);
> +	store_regs(vcpu);
>  
>  	kvm_sigset_deactivate(vcpu);
>  
> 

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Re: [PATCH v6 1/5] KVM: s390: clean up redundant 'kvm_run' parameters

[Tianjia Zhang]

On 2020/6/23 23:31, Christian Borntraeger wrote:
> 
> 
> On 23.06.20 15:14, Tianjia Zhang wrote:
>> In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
>> structure. For 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@linux.alibaba.com>
>> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>>   arch/s390/kvm/kvm-s390.c | 23 +++++++++++++++--------
>>   1 file changed, 15 insertions(+), 8 deletions(-)
> 
> Tinajia,
> 
> I have trouble seeing value in this particular patch. We add LOCs
> without providing any noticable benefit. All other patches in this series at
> least reduce the amount of code. So I would defer this to Paolo if he prefers
> to have this way across all architectures.

Yes, this is a full architecture optimization. Some of the architecture 
optimization has been merged into the mainline. I think it is necessary 
to unify this optimization. This is also the meaning of Paolo.
You can refer to the email of the previous version:
https://lkml.org/lkml/2020/4/27/16

Thanks,
Tianjia

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Re: [PATCH v6 0/5] clean up redundant 'kvm_run' parameters

[Tianjia Zhang]

Hi Paolo,

Any opinion on this series patches? Can I help with this patchset ?

Thanks and best,
Tianjia

On 2020/6/23 21:14, Tianjia Zhang wrote:
> In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
> structure. For 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.
> 
> This series of patches has completely cleaned the architecture of
> arm64, mips, ppc, and s390 (no such redundant code on x86). Due to
> the large number of modified codes, a separate patch is made for each
> platform. On the ppc platform, there is also a redundant structure
> pointer of 'kvm_run' in 'vcpu_arch', which has also been cleaned
> separately.
> 
> ---
> v6 changes:
>    Rearrange patch sets, only keep the unmerged patch.
>    rebase on mainline.
> 
> v5 change:
>    ppc: fix for review.
> 
> v4 change:
>    mips: fixes two errors in entry.c.
> 
> v3 change:
>    Keep the existing `vcpu->run` in the function body unchanged.
> 
> v2 change:
>    s390 retains the original variable name and minimizes modification.
> 
> Tianjia Zhang (5):
>    KVM: s390: clean up redundant 'kvm_run' parameters
>    KVM: arm64: clean up redundant 'kvm_run' parameters
>    KVM: PPC: clean up redundant kvm_run parameters in assembly
>    KVM: MIPS: clean up redundant 'kvm_run' parameters
>    KVM: MIPS: clean up redundant kvm_run parameters in assembly
> 
>   arch/arm64/include/asm/kvm_coproc.h   |  12 +--
>   arch/arm64/include/asm/kvm_host.h     |  11 +--
>   arch/arm64/include/asm/kvm_mmu.h      |   2 +-
>   arch/arm64/kvm/arm.c                  |   6 +-
>   arch/arm64/kvm/handle_exit.c          |  36 ++++----
>   arch/arm64/kvm/mmio.c                 |  11 +--
>   arch/arm64/kvm/mmu.c                  |   5 +-
>   arch/arm64/kvm/sys_regs.c             |  13 ++-
>   arch/mips/include/asm/kvm_host.h      |  32 ++------
>   arch/mips/kvm/emulate.c               |  59 +++++--------
>   arch/mips/kvm/entry.c                 |  21 ++---
>   arch/mips/kvm/mips.c                  |  14 ++--
>   arch/mips/kvm/trap_emul.c             | 114 +++++++++++---------------
>   arch/mips/kvm/vz.c                    |  26 +++---
>   arch/powerpc/include/asm/kvm_ppc.h    |   2 +-
>   arch/powerpc/kvm/book3s_interrupts.S  |  22 +++--
>   arch/powerpc/kvm/book3s_pr.c          |   9 +-
>   arch/powerpc/kvm/booke.c              |   9 +-
>   arch/powerpc/kvm/booke_interrupts.S   |   9 +-
>   arch/powerpc/kvm/bookehv_interrupts.S |  10 +--
>   arch/s390/kvm/kvm-s390.c              |  23 ++++--
>   21 files changed, 188 insertions(+), 258 deletions(-)
> 

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Re: [PATCH v6 1/5] KVM: s390: clean up redundant 'kvm_run' parameters

[Paolo Bonzini]

On 23/06/20 17:31, Christian Borntraeger wrote:
> 
> I have trouble seeing value in this particular patch. We add LOCs
> without providing any noticable benefit. All other patches in this series at
> least reduce the amount of code. So I would defer this to Paolo if he prefers
> to have this way across all architectures. 

Yes, it adds lines of code but they're just

+	struct kvm_run *kvm_run = vcpu->run;

You could avoid the LoC increase by repeating vcpu->run over and over,
but I think the code overall is clearer.

Paolo


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Re: [PATCH v6 3/5] KVM: PPC: clean up redundant kvm_run parameters in assembly

[Paolo Bonzini]

On 23/06/20 15:14, Tianjia Zhang wrote:
>  
>  	/* Load non-volatile guest state from the vcpu */
> -	VCPU_LOAD_NVGPRS(r4)
> +	VCPU_LOAD_NVGPRS(r3)
>  
>  kvm_start_lightweight:
>  	/* Copy registers into shadow vcpu so we can access them in real mode */
> -	mr	r3, r4
>  	bl	FUNC(kvmppc_copy_to_svcpu)
>  	nop
> -	REST_GPR(4, r1)
> +	REST_GPR(3, r1)
>  
>  #ifdef CONFIG_PPC_BOOK3S_64
>  	/* Get the dcbz32 flag */
> @@ -146,7 +144,7 @@ after_sprg3_load:

Below, there are a bunch of references to r3 and r4 left

        rldicl  r3, r3, 0, 63           /* r3 &= 1 */
        stb     r3, HSTATE_RESTORE_HID5(r13)

        /* Load up guest SPRG3 value, since it's user readable */
        lwz     r3, VCPU_SHAREDBE(r4)				  <<<
        cmpwi   r3, 0
        ld      r5, VCPU_SHARED(r4)				  <<<

where r3 is also destroyed.  So I'd rather have three patches:

- one that is as small as possible, changing the prototypes and adding

	mr r4, r3

- one that entirely swaps out r3 and r4.  This would be the hard one to
review!

- one that cleans up the prologue and epilogue

But overall I think it's simplest to just leave out this patch.

Paolo


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Re: [PATCH v6 0/5] clean up redundant 'kvm_run' parameters

[Paolo Bonzini]

On 10/07/20 09:32, Tianjia Zhang wrote:
> Hi Paolo,
> 
> Any opinion on this series patches? Can I help with this patchset ?

I was hoping to have some Tested-by, for now I'm queuing patches 1 and
2.  Thanks,

Paolo

> Thanks and best,
> Tianjia
> 
> On 2020/6/23 21:14, Tianjia Zhang wrote:
>> In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
>> structure. For 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.
>>
>> This series of patches has completely cleaned the architecture of
>> arm64, mips, ppc, and s390 (no such redundant code on x86). Due to
>> the large number of modified codes, a separate patch is made for each
>> platform. On the ppc platform, there is also a redundant structure
>> pointer of 'kvm_run' in 'vcpu_arch', which has also been cleaned
>> separately.
>>
>> ---
>> v6 changes:
>>    Rearrange patch sets, only keep the unmerged patch.
>>    rebase on mainline.
>>
>> v5 change:
>>    ppc: fix for review.
>>
>> v4 change:
>>    mips: fixes two errors in entry.c.
>>
>> v3 change:
>>    Keep the existing `vcpu->run` in the function body unchanged.
>>
>> v2 change:
>>    s390 retains the original variable name and minimizes modification.
>>
>> Tianjia Zhang (5):
>>    KVM: s390: clean up redundant 'kvm_run' parameters
>>    KVM: arm64: clean up redundant 'kvm_run' parameters
>>    KVM: PPC: clean up redundant kvm_run parameters in assembly
>>    KVM: MIPS: clean up redundant 'kvm_run' parameters
>>    KVM: MIPS: clean up redundant kvm_run parameters in assembly
>>
>>   arch/arm64/include/asm/kvm_coproc.h   |  12 +--
>>   arch/arm64/include/asm/kvm_host.h     |  11 +--
>>   arch/arm64/include/asm/kvm_mmu.h      |   2 +-
>>   arch/arm64/kvm/arm.c                  |   6 +-
>>   arch/arm64/kvm/handle_exit.c          |  36 ++++----
>>   arch/arm64/kvm/mmio.c                 |  11 +--
>>   arch/arm64/kvm/mmu.c                  |   5 +-
>>   arch/arm64/kvm/sys_regs.c             |  13 ++-
>>   arch/mips/include/asm/kvm_host.h      |  32 ++------
>>   arch/mips/kvm/emulate.c               |  59 +++++--------
>>   arch/mips/kvm/entry.c                 |  21 ++---
>>   arch/mips/kvm/mips.c                  |  14 ++--
>>   arch/mips/kvm/trap_emul.c             | 114 +++++++++++---------------
>>   arch/mips/kvm/vz.c                    |  26 +++---
>>   arch/powerpc/include/asm/kvm_ppc.h    |   2 +-
>>   arch/powerpc/kvm/book3s_interrupts.S  |  22 +++--
>>   arch/powerpc/kvm/book3s_pr.c          |   9 +-
>>   arch/powerpc/kvm/booke.c              |   9 +-
>>   arch/powerpc/kvm/booke_interrupts.S   |   9 +-
>>   arch/powerpc/kvm/bookehv_interrupts.S |  10 +--
>>   arch/s390/kvm/kvm-s390.c              |  23 ++++--
>>   21 files changed, 188 insertions(+), 258 deletions(-)
>>
> 


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Re: [PATCH v6 3/5] KVM: PPC: clean up redundant kvm_run parameters in assembly

[Paul Mackerras]

On Tue, Jun 23, 2020 at 09:14:16PM +0800, Tianjia Zhang wrote:
> In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
> structure. For 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.

Thanks, patch applied to my kvm-ppc-next branch, with fixes.

Paul.

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