linux-kernel - Re: [PATCHv5 05/12] efi/x86: Implement support for unaccepted memory

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Date:   Fri, 29 Apr 2022 12:53:30 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        Ard Biesheuvel <ardb@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Varad Gautam <varad.gautam@...e.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>, x86@...nel.org,
        linux-mm@...ck.org, linux-coco@...ts.linux.dev,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv5 05/12] efi/x86: Implement support for unaccepted memory

On Mon, Apr 25, 2022 at 06:39:27AM +0300, Kirill A. Shutemov wrote:
> diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
> index 5401985901f5..f9b88174209e 100644
> --- a/drivers/firmware/efi/libstub/x86-stub.c
> +++ b/drivers/firmware/efi/libstub/x86-stub.c
> @@ -15,6 +15,7 @@
>  #include <asm/setup.h>
>  #include <asm/desc.h>
>  #include <asm/boot.h>
> +#include <asm/unaccepted_memory.h>
>  
>  #include "efistub.h"
>  
> @@ -504,6 +505,17 @@ setup_e820(struct boot_params *params, struct setup_data *e820ext, u32 e820ext_s
>  			e820_type = E820_TYPE_PMEM;
>  			break;
>  
> +		case EFI_UNACCEPTED_MEMORY:
> +			if (!IS_ENABLED(CONFIG_UNACCEPTED_MEMORY)) {
> +				efi_warn_once("The system has unaccepted memory,"
> +					     " but kernel does not support it\n");
> +				efi_warn_once("Consider enabling UNACCEPTED_MEMORY\n");

CONFIG_UNACCEPTED_MEMORY

> +				continue;
> +			}
> +			e820_type = E820_TYPE_RAM;
> +			process_unaccepted_memory(params, d->phys_addr,
> +					d->phys_addr + PAGE_SIZE * d->num_pages);

Align arguments on the opening brace.

> +			break;
>  		default:
>  			continue;
>  		}
> @@ -568,6 +580,59 @@ static efi_status_t alloc_e820ext(u32 nr_desc, struct setup_data **e820ext,
>  	return status;
>  }
>  
> +static efi_status_t allocate_unaccepted_memory(struct boot_params *params,
> +					       __u32 nr_desc,
> +					       struct efi_boot_memmap *map)
> +{
> +	unsigned long *mem = NULL;
> +	u64 size, max_addr = 0;
> +	efi_status_t status;
> +	bool found = false;
> +	int i;
> +
> +	/* Check if there's any unaccepted memory and find the max address */
> +	for (i = 0; i < nr_desc; i++) {
> +		efi_memory_desc_t *d;
> +
> +		d = efi_early_memdesc_ptr(*map->map, *map->desc_size, i);
> +		if (d->type == EFI_UNACCEPTED_MEMORY)
> +			found = true;
> +		if (d->phys_addr + d->num_pages * PAGE_SIZE > max_addr)
> +			max_addr = d->phys_addr + d->num_pages * PAGE_SIZE;
> +	}
> +
> +	if (!found) {
> +		params->unaccepted_memory = 0;
> +		return EFI_SUCCESS;
> +	}
> +
> +	/*
> +	 * If unaccepted memory is present allocate a bitmap to track what
> +	 * memory has to be accepted before access.
> +	 *
> +	 * One bit in the bitmap represents 2MiB in the address space:
> +	 * A 4k bitmap can track 64GiB of physical address space.
> +	 *
> +	 * In the worst case scenario -- a huge hole in the middle of the
> +	 * address space -- It needs 256MiB to handle 4PiB of the address
> +	 * space.
> +	 *
> +	 * TODO: handle situation if params->unaccepted_memory has already set.

"... is already set."

And when is that TODO taken care of? Later patch or patchset?

Thx.

-- 
Regards/Gruss,
    Boris.

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