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From: Paolo Bonzini <pbonzini@redhat.com>
To: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
	tsbogend@alpha.franken.de, paulus@ozlabs.org, mpe@ellerman.id.au,
	benh@kernel.crashing.org, borntraeger@de.ibm.com,
	frankja@linux.ibm.com, david@redhat.com, cohuck@redhat.com,
	heiko.carstens@de.ibm.com, gor@linux.ibm.com,
	sean.j.christopherson@intel.com, vkuznets@redhat.com,
	wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org,
	tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	x86@kernel.org, hpa@zytor.com, maz@kernel.org,
	james.morse@arm.com, julien.thierry.kdev@gmail.com,
	suzuki.poulose@arm.com, christoffer.dall@arm.com,
	peterx@redhat.com, thuth@redhat.com, chenhuacai@gmail.com
Cc: linux-s390@vger.kernel.org, kvm@vger.kernel.org,
	linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v6 3/5] KVM: PPC: clean up redundant kvm_run parameters in assembly
Date: Fri, 10 Jul 2020 09:57:02 +0200
Message-ID: <8947174f-ce16-c076-e208-55e743d9fdf0@redhat.com> (raw)
In-Reply-To: <20200623131418.31473-4-tianjia.zhang@linux.alibaba.com>

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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Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23 13:14 [PATCH v6 0/5] clean up redundant 'kvm_run' parameters Tianjia Zhang
2020-06-23 13:14 ` [PATCH v6 1/5] KVM: s390: " Tianjia Zhang
2020-06-23 15:31   ` Christian Borntraeger
2020-06-24  2:39     ` Tianjia Zhang
2020-07-10  7:48     ` Paolo Bonzini
2020-06-23 13:14 ` [PATCH v6 2/5] KVM: arm64: " Tianjia Zhang
2020-06-23 13:14 ` [PATCH v6 3/5] KVM: PPC: clean up redundant kvm_run parameters in assembly Tianjia Zhang
2020-07-10  7:57   ` Paolo Bonzini [this message]
2020-07-23  6:19   ` Paul Mackerras
2020-06-23 13:14 ` [PATCH v6 4/5] KVM: MIPS: clean up redundant 'kvm_run' parameters Tianjia Zhang
2020-06-23 13:14 ` [PATCH v6 5/5] KVM: MIPS: clean up redundant kvm_run parameters in assembly Tianjia Zhang
2020-07-10  7:32 ` [PATCH v6 0/5] clean up redundant 'kvm_run' parameters Tianjia Zhang
2020-07-10  8:06   ` Paolo Bonzini

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