linux-kernel - Re: [PATCH v2] KVM: arm/arm64: Fix external abort type matching

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Message-ID: <86efpoabed.fsf@arm.com>
Date:   Fri, 27 Oct 2017 15:55:06 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Dongjiu Geng <gengdongjiu@...wei.com>
Cc:     <christoffer.dall@...aro.org>, <linux@...linux.org.uk>,
        <james.morse@....com>, <tbaicar@...eaurora.org>,
        <catalin.marinas@....com>, <will.deacon@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] KVM: arm/arm64: Fix external abort type matching

On Thu, Oct 26 2017 at  6:07:01 pm BST, Dongjiu Geng <gengdongjiu@...wei.com> wrote:
> For this matching, current code using the {I,D}FSC
> range to match kvm_vcpu_trap_get_fault_type() return
> value, but kvm_vcpu_trap_get_fault_type() only return
> the part {I,D}FSC instead of whole, so fix this issue
>
> Value       Type
> 0x10        FSC_SEA
> 0x14        FSC_SEA_TTW0 FSC_SEA_TTW1 FSC_SEA_TTW2 FSC_SEA_TTW3
> 0x18        FSC_SECC
> 0x1c        FSC_SECC_TTW0 FSC_SECC_TTW1 FSC_SECC_TTW2 FSC_SECC_TTW3
>
> CC: James Morse <james.morse@....com>
> CC: Tyler Baicar <tbaicar@...eaurora.org>
> Signed-off-by: Dongjiu Geng <gengdongjiu@...wei.com>
>
> ---
> As shown below code:
>
> The kvm_vcpu_trap_get_fault_type() only return {I,D}FSC bit[5]:bit[2], not
> the whole {I,D}FSC, but FSC_SEA_TTWx and FSC_SECC_TTWx are the whole {I,D}FSC
> value.
>
> static inline u8 kvm_vcpu_trap_get_fault_type(const struct kvm_vcpu *vcpu)
> {
>     return kvm_vcpu_get_hsr(vcpu) & ESR_ELx_FSC_TYPE;
> }
>
> static inline bool kvm_vcpu_dabt_isextabt(const struct kvm_vcpu *vcpu)
> {
>     switch (kvm_vcpu_trap_get_fault_type(vcpu)) {
>     case FSC_SEA:
>     case FSC_SEA_TTW0:
>     case FSC_SEA_TTW1:
>     case FSC_SEA_TTW2:
>     case FSC_SEA_TTW3:
>     case FSC_SECC:
>     case FSC_SECC_TTW0:
>     case FSC_SECC_TTW1:
>     case FSC_SECC_TTW2:
>     case FSC_SECC_TTW3:
>         return true;
>     default:
>         return false;
>     }
> }
> ---
>  arch/arm/include/asm/kvm_arm.h       | 10 ++--------
>  arch/arm/include/asm/kvm_emulate.h   | 10 ++--------
>  arch/arm64/include/asm/kvm_arm.h     | 10 ++--------
>  arch/arm64/include/asm/kvm_emulate.h | 10 ++--------
>  4 files changed, 8 insertions(+), 32 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_arm.h b/arch/arm/include/asm/kvm_arm.h
> index c878145..b4b155c 100644
> --- a/arch/arm/include/asm/kvm_arm.h
> +++ b/arch/arm/include/asm/kvm_arm.h
> @@ -188,15 +188,9 @@
>  #define FSC_ACCESS	(0x08)
>  #define FSC_PERM	(0x0c)
>  #define FSC_SEA		(0x10)
> -#define FSC_SEA_TTW0	(0x14)
> -#define FSC_SEA_TTW1	(0x15)
> -#define FSC_SEA_TTW2	(0x16)
> -#define FSC_SEA_TTW3	(0x17)
> +#define FSC_SEA_TTW	(0x14)
>  #define FSC_SECC	(0x18)
> -#define FSC_SECC_TTW0	(0x1c)
> -#define FSC_SECC_TTW1	(0x1d)
> -#define FSC_SECC_TTW2	(0x1e)
> -#define FSC_SECC_TTW3	(0x1f)
> +#define FSC_SECC_TTW	(0x1c)
>  
>  /* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
>  #define HPFAR_MASK	(~0xf)
> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
> index 98089ff..aed8279 100644
> --- a/arch/arm/include/asm/kvm_emulate.h
> +++ b/arch/arm/include/asm/kvm_emulate.h
> @@ -205,15 +205,9 @@ static inline bool kvm_vcpu_dabt_isextabt(struct kvm_vcpu *vcpu)
>  {
>  	switch (kvm_vcpu_trap_get_fault_type(vcpu)) {
>  	case FSC_SEA:
> -	case FSC_SEA_TTW0:
> -	case FSC_SEA_TTW1:
> -	case FSC_SEA_TTW2:
> -	case FSC_SEA_TTW3:
> +	case FSC_SEA_TTW:
>  	case FSC_SECC:
> -	case FSC_SECC_TTW0:
> -	case FSC_SECC_TTW1:
> -	case FSC_SECC_TTW2:
> -	case FSC_SECC_TTW3:
> +	case FSC_SECC_TTW:
>  		return true;
>  	default:
>  		return false;
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 61d694c..c0f1798 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -205,15 +205,9 @@
>  #define FSC_ACCESS	ESR_ELx_FSC_ACCESS
>  #define FSC_PERM	ESR_ELx_FSC_PERM
>  #define FSC_SEA		ESR_ELx_FSC_EXTABT
> -#define FSC_SEA_TTW0	(0x14)
> -#define FSC_SEA_TTW1	(0x15)
> -#define FSC_SEA_TTW2	(0x16)
> -#define FSC_SEA_TTW3	(0x17)
> +#define FSC_SEA_TTW	(0x14)
>  #define FSC_SECC	(0x18)
> -#define FSC_SECC_TTW0	(0x1c)
> -#define FSC_SECC_TTW1	(0x1d)
> -#define FSC_SECC_TTW2	(0x1e)
> -#define FSC_SECC_TTW3	(0x1f)
> +#define FSC_SECC_TTW	(0x1c)
>  
>  /* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
>  #define HPFAR_MASK	(~UL(0xf))
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index e5df3fc..5cde311 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -239,15 +239,9 @@ static inline bool kvm_vcpu_dabt_isextabt(const struct kvm_vcpu *vcpu)
>  {
>  	switch (kvm_vcpu_trap_get_fault_type(vcpu)) {
>  	case FSC_SEA:
> -	case FSC_SEA_TTW0:
> -	case FSC_SEA_TTW1:
> -	case FSC_SEA_TTW2:
> -	case FSC_SEA_TTW3:
> +	case FSC_SEA_TTW:
>  	case FSC_SECC:
> -	case FSC_SECC_TTW0:
> -	case FSC_SECC_TTW1:
> -	case FSC_SECC_TTW2:
> -	case FSC_SECC_TTW3:
> +	case FSC_SECC_TTW:
>  		return true;
>  	default:
>  		return false;

What is the bug you're fixing? From what I can tell, you're simply
removing valuable symbols from the kernel, and inventing another one
that doesn't exist in the architecture.

If you were instead adding an accessor for the full fault syndrome, then
that would be a useful addition. But as it is, this patch looks
completely pointless.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.