Date:   Mon, 6 Mar 2023 17:54:15 +0530
From:   Kautuk Consul <kconsul@linux.vnet.ibm.com>
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
        Fabiano Rosas <farosas@linux.ibm.com>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        Sathvika Vasireddy <sv@linux.ibm.com>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] arch/powerpc/kvm: kvmppc_hv_entry: remove r4 argument
Message-ID: <ZAXbb9shzU+6l0wh@li-a450e7cc-27df-11b2-a85c-b5a9ac31e8ef.ibm.com>
References: <20230220052355.109033-1-kconsul@linux.vnet.ibm.com>
 <20230220052355.109033-3-kconsul@linux.vnet.ibm.com>
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In-Reply-To: <20230220052355.109033-3-kconsul@linux.vnet.ibm.com>
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Hi,

On 2023-02-20 10:53:55, Kautuk Consul wrote:
> kvmppc_hv_entry is called from only 2 locations within
> book3s_hv_rmhandlers.S. Both of those locations set r4
> as HSTATE_KVM_VCPU(r13) before calling kvmppc_hv_entry.
> So, shift the r4 load instruction to kvmppc_hv_entry and
> thus modify the calling convention of this function.
> 

I am posting v2 of this patch-set now.
I have tested this on POWER8 and it works fine.
Can anyone review the v2 for this patch ? 
I didn't receive any review comments for this patch.

> Signed-off-by: Kautuk Consul <kconsul@linux.vnet.ibm.com>
> ---
>  arch/powerpc/kvm/book3s_hv_rmhandlers.S | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> index 7e063fde7adc..922667b09168 100644
> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> @@ -85,7 +85,7 @@ _GLOBAL_TOC(kvmppc_hv_entry_trampoline)
>  	RFI_TO_KERNEL
> 
>  kvmppc_call_hv_entry:
> -	ld	r4, HSTATE_KVM_VCPU(r13)
> +	/* Enter guest. */
>  	bl	kvmppc_hv_entry
> 
>  	/* Back from guest - restore host state and return to caller */
> @@ -352,9 +352,7 @@ kvm_secondary_got_guest:
>  	mtspr	SPRN_LDBAR, r0
>  	isync
>  63:
> -	/* Order load of vcpu after load of vcore */
> -	lwsync
> -	ld	r4, HSTATE_KVM_VCPU(r13)
> +	/* Enter guest. */
>  	bl	kvmppc_hv_entry
> 
>  	/* Back from the guest, go back to nap */
> @@ -506,7 +504,6 @@ kvmppc_hv_entry:
> 
>  	/* Required state:
>  	 *
> -	 * R4 = vcpu pointer (or NULL)
>  	 * MSR = ~IR|DR
>  	 * R13 = PACA
>  	 * R1 = host R1
> @@ -524,6 +521,8 @@ kvmppc_hv_entry:
>  	li	r6, KVM_GUEST_MODE_HOST_HV
>  	stb	r6, HSTATE_IN_GUEST(r13)
> 
> +	ld	r4, HSTATE_KVM_VCPU(r13)
> +
>  #ifdef CONFIG_KVM_BOOK3S_HV_P8_TIMING
>  	/* Store initial timestamp */
>  	cmpdi	r4, 0
> -- 
> 2.31.1
>