linux-kernel - Re: [PATCH v7 1/3] efi/x86: Fix EFI memory map corruption with kexec

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Date: Mon, 3 Jun 2024 18:31:13 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: "Kalra, Ashish" <ashish.kalra@....com>, tglx@...utronix.de,
	mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org,
	rafael@...nel.org, hpa@...or.com, peterz@...radead.org,
	adrian.hunter@...el.com, sathyanarayanan.kuppuswamy@...ux.intel.com,
	jun.nakajima@...el.com, rick.p.edgecombe@...el.com,
	thomas.lendacky@....com, michael.roth@....com, seanjc@...gle.com,
	kai.huang@...el.com, bhe@...hat.com,
	kirill.shutemov@...ux.intel.com, bdas@...hat.com,
	vkuznets@...hat.com, dionnaglaze@...gle.com, anisinha@...hat.com,
	jroedel@...e.de, ardb@...nel.org, kexec@...ts.infradead.org,
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/3] efi/x86: Fix EFI memory map corruption with kexec

On Mon, Jun 03, 2024 at 04:46:39PM +0200, Borislav Petkov wrote:
> On Mon, Jun 03, 2024 at 09:01:49AM -0500, Kalra, Ashish wrote:
> > If we skip efi_arch_mem_reserve() (which should probably be anyway skipped
> > for kexec case), then for kexec boot, EFI memmap is memremapped in the same
> > virtual address as the first kernel and not the allocated memblock address.
> 
> Are you saying that we should simply do
> 
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index fdf07dd6f459..410cb0743289 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -577,6 +577,9 @@ void __init efi_mem_reserve(phys_addr_t addr, u64 size)
>  	if (WARN_ON_ONCE(efi_enabled(EFI_PARAVIRT)))
>  		return;
>  
> +	if (kexec_in_progress)
> +		return;
> +
>  	if (!memblock_is_region_reserved(addr, size))
>  		memblock_reserve(addr, size);
>  
> and skip that whole call?

I think Ashish suggested rather 

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index fdf07dd6f459..eccc10ab15a4 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -580,6 +580,9 @@ void __init efi_mem_reserve(phys_addr_t addr, u64 size)
 	if (!memblock_is_region_reserved(addr, size))
 		memblock_reserve(addr, size);
 
+	if (kexec_in_progress)
+		return;
+
 	/*
 	 * Some architectures (x86) reserve all boot services ranges
 	 * until efi_free_boot_services() because of buggy firmware
 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette

-- 
Sincerely yours,
Mike.