linux-kernel - RE: [PATCH v2 1/1] x86/hyperv: Use Hyper-V entropy to seed guest random number generator

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Message-ID:
 <SJ1PR21MB34571493BC1473790F5917E0CE2A2@SJ1PR21MB3457.namprd21.prod.outlook.com>
Date: Wed, 13 Mar 2024 04:50:59 +0000
From: Long Li <longli@...rosoft.com>
To: "mhklinux@...look.com" <mhklinux@...look.com>, Haiyang Zhang
	<haiyangz@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>, Dexuan
 Cui <decui@...rosoft.com>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>, "hpa@...or.com"
	<hpa@...or.com>, "arnd@...db.de" <arnd@...db.de>, "tytso@....edu"
	<tytso@....edu>, jason <jason@...c4.com>, "x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: RE: [PATCH v2 1/1] x86/hyperv: Use Hyper-V entropy to seed guest
 random number generator

> +void __init ms_hyperv_late_init(void)
> +{
> +       struct acpi_table_header *header;
> +       acpi_status status;
> +       u8 *randomdata;
> +       u32 length, i;
> +
> +       /*
> +        * Seed the Linux random number generator with entropy provided by
> +        * the Hyper-V host in ACPI table OEM0.  It would be nice to do this
> +        * even earlier in ms_hyperv_init_platform(), but the ACPI subsystem
> +        * isn't set up at that point. Skip if booted via EFI as generic EFI
> +        * code has already done some seeding using the EFI RNG protocol.
> +        */
> +       if (!IS_ENABLED(CONFIG_ACPI) || efi_enabled(EFI_BOOT))
> +               return;
> +
> +       status = acpi_get_table("OEM0", 0, &header);
> +       if (ACPI_FAILURE(status) || !header)
> +               return;

Should we call acpi_put_table() if header == 0? It will also be helpful doing a pr_info() here so user knows that hyper-v random number is not used.