Subject: Re: linux-next: manual merge of the kvm-arm tree with the arm64 tree

From: Stephen Rothwell <[email-masked]>
Date: Fri, 21 Mar 2025 15:29:55 +1100

Hi all,

On Mon, 17 Mar 2025 17:17:01 +1100 Stephen Rothwell <[email-masked]> wrote:
> 
> Today's linux-next merge of the kvm-arm tree got a conflict in:
> 
>   arch/arm64/kernel/proton-pack.c
> 
> between commits:
> 
>   e403e8538359 ("arm64: errata: Assume that unknown CPUs _are_ vulnerable to Spectre BHB")
>   a5951389e58d ("arm64: errata: Add newer ARM cores to the spectre_bhb_loop_affected() lists")
> 
> from the arm64 tree and commit:
> 
>   e3121298c7fc ("arm64: Modify _midr_range() functions to read MIDR/REVIDR internally")
> 
> from the kvm-arm tree.
> 
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging.  You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
> 
> 
> diff --cc arch/arm64/kernel/proton-pack.c
> index 0f51fd10b4b0,a573fa40d4b6..000000000000
> --- a/arch/arm64/kernel/proton-pack.c
> +++ b/arch/arm64/kernel/proton-pack.c
> @@@ -845,86 -845,52 +845,86 @@@ static unsigned long system_bhb_mitigat
>    * This must be called with SCOPE_LOCAL_CPU for each type of CPU, before any
>    * SCOPE_SYSTEM call will give the right answer.
>    */
>  -u8 spectre_bhb_loop_affected(int scope)
>  +static bool is_spectre_bhb_safe(int scope)
>  +{
>  +	static const struct midr_range spectre_bhb_safe_list[] = {
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A35),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A53),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A55),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A510),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A520),
>  +		MIDR_ALL_VERSIONS(MIDR_BRAHMA_B53),
>  +		MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_2XX_SILVER),
>  +		MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_3XX_SILVER),
>  +		MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_SILVER),
>  +		{},
>  +	};
>  +	static bool all_safe = true;
>  +
>  +	if (scope != SCOPE_LOCAL_CPU)
>  +		return all_safe;
>  +
> - 	if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_safe_list))
> ++	if (is_midr_in_range_list(spectre_bhb_safe_list))
>  +		return true;
>  +
>  +	all_safe = false;
>  +
>  +	return false;
>  +}
>  +
>  +static u8 spectre_bhb_loop_affected(void)
>   {
>   	u8 k = 0;
>  -	static u8 max_bhb_k;
>   
>  -	if (scope == SCOPE_LOCAL_CPU) {
>  -		static const struct midr_range spectre_bhb_k32_list[] = {
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_A78),
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_A78AE),
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_A78C),
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_X1),
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_A710),
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_X2),
>  -			MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N2),
>  -			MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V1),
>  -			{},
>  -		};
>  -		static const struct midr_range spectre_bhb_k24_list[] = {
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_A76),
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_A77),
>  -			MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
>  -			{},
>  -		};
>  -		static const struct midr_range spectre_bhb_k11_list[] = {
>  -			MIDR_ALL_VERSIONS(MIDR_AMPERE1),
>  -			{},
>  -		};
>  -		static const struct midr_range spectre_bhb_k8_list[] = {
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
>  -			MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
>  -			{},
>  -		};
>  +	static const struct midr_range spectre_bhb_k132_list[] = {
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_X3),
>  +		MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V2),
>  +	};
>  +	static const struct midr_range spectre_bhb_k38_list[] = {
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A715),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A720),
>  +	};
>  +	static const struct midr_range spectre_bhb_k32_list[] = {
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A78),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A78AE),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A78C),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_X1),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A710),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_X2),
>  +		MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N2),
>  +		MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V1),
>  +		{},
>  +	};
>  +	static const struct midr_range spectre_bhb_k24_list[] = {
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A76),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A76AE),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A77),
>  +		MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
>  +		MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_GOLD),
>  +		{},
>  +	};
>  +	static const struct midr_range spectre_bhb_k11_list[] = {
>  +		MIDR_ALL_VERSIONS(MIDR_AMPERE1),
>  +		{},
>  +	};
>  +	static const struct midr_range spectre_bhb_k8_list[] = {
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
>  +		MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
>  +		{},
>  +	};
>   
> - 	if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k132_list))
>  -		if (is_midr_in_range_list(spectre_bhb_k32_list))
>  -			k = 32;
>  -		else if (is_midr_in_range_list(spectre_bhb_k24_list))
>  -			k = 24;
>  -		else if (is_midr_in_range_list(spectre_bhb_k11_list))
>  -			k = 11;
>  -		else if (is_midr_in_range_list(spectre_bhb_k8_list))
>  -			k =  8;
>  -
>  -		max_bhb_k = max(max_bhb_k, k);
>  -	} else {
>  -		k = max_bhb_k;
>  -	}
> ++	if (is_midr_in_range_list(spectre_bhb_k132_list))
>  +		k = 132;
> - 	else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k38_list))
> ++	else if (is_midr_in_range_list(spectre_bhb_k38_list))
>  +		k = 38;
> - 	else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k32_list))
> ++	else if (is_midr_in_range_list(spectre_bhb_k32_list))
>  +		k = 32;
> - 	else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k24_list))
> ++	else if (is_midr_in_range_list(spectre_bhb_k24_list))
>  +		k = 24;
> - 	else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k11_list))
> ++	else if (is_midr_in_range_list(spectre_bhb_k11_list))
>  +		k = 11;
> - 	else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k8_list))
> ++	else if (is_midr_in_range_list(spectre_bhb_k8_list))
>  +		k =  8;
>   
>   	return k;
>   }

This is now a conflict between the kvm tree and the arm64 tree.

-- 
Cheers,
Stephen Rothwell