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Date: Tue, 4 Jun 2024 21:08:55 -0500
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Subject: Re: [PATCH v7 1/3] efi/x86: Fix EFI memory map corruption with kexec
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To: Dave Young <dyoung@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>, Mike Rapoport <rppt@kernel.org>,
 tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com,
 x86@kernel.org, rafael@kernel.org, hpa@zytor.com, peterz@infradead.org,
 adrian.hunter@intel.com, sathyanarayanan.kuppuswamy@linux.intel.com,
 jun.nakajima@intel.com, rick.p.edgecombe@intel.com, thomas.lendacky@amd.com,
 michael.roth@amd.com, seanjc@google.com, kai.huang@intel.com,
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 jroedel@suse.de, ardb@kernel.org, kexec@lists.infradead.org,
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References: <f4be03b8488665f56a1e5c6e6459f447352dfcf5.1717111180.git.ashish.kalra@amd.com>
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From: "Kalra, Ashish" <ashish.kalra@amd.com>
In-Reply-To: <CALu+AoSESmasAHqWdCGgQNbsTXfwbfhERBkaqSeaX881zqKtFg@mail.gmail.com>
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Hello Dave,

On 6/4/2024 8:58 PM, Dave Young wrote:
> On Wed, 5 Jun 2024 at 09:52, Dave Young <dyoung@redhat.com> wrote:
>>>>         ...
>>>>         if (efi.memmap.flags & (EFI_MEMMAP_MEMBLOCK | EFI_MEMMAP_SLAB)) {
>>>>                 __efi_memmap_free(efi.memmap.phys_map,
>>>>                                 efi.memmap.desc_size * efi.memmap.nr_map, efi.memmap.flags);
>>>>         }
>>> From your debugging the memmap should not be freed.  This piece of
>>> code was added in below commit,  added Dan Williams in cc list:
>>> commit f0ef6523475f18ccd213e22ee593dfd131a2c5ea
>>> Author: Dan Williams <dan.j.williams@intel.com>
>>> Date:   Mon Jan 13 18:22:44 2020 +0100
>>>
>>>     efi: Fix efi_memmap_alloc() leaks
>>>
>>>     With efi_fake_memmap() and efi_arch_mem_reserve() the efi table may be
>>>     updated and replaced multiple times. When that happens a previous
>>>     dynamically allocated efi memory map can be garbage collected. Use the
>>>     new EFI_MEMMAP_{SLAB,MEMBLOCK} flags to detect when a dynamically
>>>     allocated memory map is being replaced.
>>>
>> Dan, probably those regions should be freed only for "fake" memmap?
> Ashish, can you comment out the __efi_memmap_free see if it works for
> you just confirm about the behavior.

Yes, i have already tried and tested that, if i avoid __efi_memmap_free(), then i don't see this memory map corruption.

Thanks, Ashish