linux-kernel - Re: [PATCH V2 1/2] efi/unaccepted: Do not let /proc/vmcore try to access unaccepted memory

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Message-ID: <7f4881dc-885a-a8f5-47a5-0dd23886a416@redhat.com>
Date:   Tue, 12 Sep 2023 09:18:30 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ard Biesheuvel <ardb@...nel.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Dave Young <dyoung@...hat.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-coco@...ts.linux.dev, linux-efi@...r.kernel.org,
        kexec@...ts.infradead.org
Subject: Re: [PATCH V2 1/2] efi/unaccepted: Do not let /proc/vmcore try to
 access unaccepted memory

On 11.09.23 13:21, Adrian Hunter wrote:
> Support for unaccepted memory was added recently, refer commit dcdfdd40fa82
> ("mm: Add support for unaccepted memory"), whereby a virtual machine may
> need to accept memory before it can be used.
> 
> Do not let /proc/vmcore try to access unaccepted memory because it can
> cause the guest to fail.
> 
> For /proc/vmcore, which is read-only, this means a read or mmap of
> unaccepted memory will return zeros.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---

[...]

> +static inline bool pfn_is_unaccepted_memory(unsigned long pfn)
> +{
> +	phys_addr_t paddr = pfn << PAGE_SHIFT;
> +
> +	return range_contains_unaccepted_memory(paddr, paddr + PAGE_SIZE);
> +}
> +
>   #endif /* _LINUX_MM_H */

As stated, if the relevant table is not already properly populated with 
information about unaccepted memory by the first kernel, this probably 
logically belongs into Kirills series.

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb