linux-kernel - Re: [RFC PATCH v4 14/28] Add support to access boot related data in the clear

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Date:   Fri, 17 Mar 2017 14:50:14 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Dave Young <dyoung@...hat.com>
CC:     <linux-arch@...r.kernel.org>, <linux-efi@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
        <iommu@...ts.linux-foundation.org>, Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Larry Woodman <lwoodman@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v4 14/28] Add support to access boot related data in
 the clear

On 3/8/2017 12:55 AM, Dave Young wrote:
> On 02/16/17 at 09:45am, Tom Lendacky wrote:
> [snip]
>> + * This function determines if an address should be mapped encrypted.
>> + * Boot setup data, EFI data and E820 areas are checked in making this
>> + * determination.
>> + */
>> +static bool memremap_should_map_encrypted(resource_size_t phys_addr,
>> +					  unsigned long size)
>> +{
>> +	/*
>> +	 * SME is not active, return true:
>> +	 *   - For early_memremap_pgprot_adjust(), returning true or false
>> +	 *     results in the same protection value
>> +	 *   - For arch_memremap_do_ram_remap(), returning true will allow
>> +	 *     the RAM remap to occur instead of falling back to ioremap()
>> +	 */
>> +	if (!sme_active())
>> +		return true;
>
> From the function name shouldn't above be return false?

I've re-worked this so that the check is in a different location and
doesn't cause confusion.

>
>> +
>> +	/* Check if the address is part of the setup data */
>> +	if (memremap_is_setup_data(phys_addr, size))
>> +		return false;
>> +
>> +	/* Check if the address is part of EFI boot/runtime data */
>> +	switch (efi_mem_type(phys_addr)) {
>> +	case EFI_BOOT_SERVICES_DATA:
>> +	case EFI_RUNTIME_SERVICES_DATA:
>
> Only these two types needed? I'm not sure about this, just bring up the
> question.

I've re-worked this code so that there is a single EFI routine that
checks boot_params.efi_info.efi_memmap/efi_systab, EFI tables and the
EFI memtype.  As for the EFI memtypes, I believe those are the only
ones required.  Some of the other types will be picked up by the e820
checks (ACPI, NVS, etc.).

Thanks,
Tom

>
>> +		return false;
>> +	default:
>> +		break;
>> +	}
>> +
>> +	/* Check if the address is outside kernel usable area */
>> +	switch (e820__get_entry_type(phys_addr, phys_addr + size - 1)) {
>> +	case E820_TYPE_RESERVED:
>> +	case E820_TYPE_ACPI:
>> +	case E820_TYPE_NVS:
>> +	case E820_TYPE_UNUSABLE:
>> +		return false;
>> +	default:
>> +		break;
>> +	}
>> +
>> +	return true;
>> +}
>> +
>
> Thanks
> Dave
>