linux-kernel - RE: [PATCH v13 00/11] Parallel CPU bringup for x86

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Date:   Wed, 8 Mar 2023 12:15:56 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'David Woodhouse' <dwmw2@...radead.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Usama Arif <usama.arif@...edance.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Phillips, Kim" <kim.phillips@....com>,
        "brgerst@...il.com" <brgerst@...il.com>,
        "Rapan, Sabin" <sabrapan@...zon.com>
CC:     "piotrgorski@...hyos.org" <piotrgorski@...hyos.org>,
        "oleksandr@...alenko.name" <oleksandr@...alenko.name>,
        "arjan@...ux.intel.com" <arjan@...ux.intel.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
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        "liangma@...ngbit.com" <liangma@...ngbit.com>
Subject: RE: [PATCH v13 00/11] Parallel CPU bringup for x86_64

From: David Woodhouse
> Sent: 08 March 2023 09:05
...
> https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/parallel-6.2-v14
> 
> Looks like this:
> 
> /*
>  * We can do 64-bit AP bringup in parallel if the CPU reports its APIC
>  * ID in CPUID (either leaf 0x0B if we need the full APIC ID in X2APIC
>  * mode, or leaf 0x01 if 8 bits are sufficient). Otherwise it's too
>  * hard.
>  */
> static bool prepare_parallel_bringup(void)
> {
> 	bool has_sev_es = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT) &&
> 		static_branch_unlikely(&sev_es_enable_key);
> 
> 	if (IS_ENABLED(CONFIG_X86_32))
> 		return false;
> 
> 	/*
> 	 * Encrypted guests other than SEV-ES (in the future) will need to
> 	 * implement an early way of finding the APIC ID, since they will
> 	 * presumably block direct CPUID too. Be kind to our future selves
> 	 * by warning here instead of just letting them break. Parallel
> 	 * startup doesn't have to be in the first round of enabling patches
> 	 * for any such technology.
> 	 */
> 	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT) || !has_sev_es) {
> 		pr_info("Disabling parallel bringup due to guest memory encryption\n");
> 		return false;
> 	}

That looks wrong, won't has_sev_es almost always be false
so it prints the message and returns?
Maybe s/||/&&/ ?

	David

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