linux-kernel - Re: [PATCH] x86/boot: Use EFI setup data if provided

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Message-ID: <20190325060128.GB9385@dhcp-128-65.nay.redhat.com>
Date:   Mon, 25 Mar 2019 14:01:28 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Junichi Nomura <j-nomura@...jp.nec.com>
Cc:     Borislav Petkov <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "fanc.fnst@...fujitsu.com" <fanc.fnst@...fujitsu.com>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "bp@...e.de" <bp@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/boot: Use EFI setup data if provided

On 03/25/19 at 12:27am, Junichi Nomura wrote:
> On Fri, Mar 22, 2019 at 04:23:28PM +0100, Borislav Petkov wrote:
> > On Fri, Mar 22, 2019 at 11:03:43AM +0000, Junichi Nomura wrote:
> > > Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
> > > boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
> > > in the early parsing code tries to search RSDP from EFI table but
> > > whose address is virtual.
> > > 
> > > Since kexec(1) provides physical address of config_table via boot_params,
> > > efi_get_rsdp_addr() should look for setup_data in the same way as
> > > efi_systab_init() in arch/x86/platform/efi/efi.c does.
> > 
> > If the kexec kernel should continue to use efi_systab_init() then you
> > should make efi_get_rsdp_addr() exit early in the kexec-ed kernel.
> 
> I'm not sure which way kexec devel is going. Added kexec list.
> Here is the version that exits early in efi_get_rsdp_addr().
> 
> [PATCH] x86/boot: Don't try to search RSDP from EFI when kexec-booted
> 
> Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
> boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
> in the early parsing code tries to search RSDP from EFI table but
> whose address is virtual.
> 
> Normally kexec(1) provides physical address of config_table via boot_params
> and EFI code uses that during initialization.
> For the early boot code, we just exit efi_get_rsdp_addr() early if the kernel
> is booted by kexec.
> 
> Fixes: 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in boot_params")
> Signed-off-by: Jun'ichi Nomura <j-nomura@...jp.nec.com>
> Cc: Chao Fan <fanc.fnst@...fujitsu.com>
> Cc: Borislav Petkov <bp@...e.de>
> 
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index 0ef4ad5..1cefc43 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -44,6 +44,24 @@ static acpi_physical_address get_acpi_rsdp(void)
>  	return addr;
>  }
>  
> +static bool is_kexec_booted(void)
> +{
> +	struct setup_data *data;
> +
> +	/*
> +	 * kexec-tools provides EFI setup data so that kexec-ed kernel
> +	 * can find proper tables.
> +	 */
> +	data = (struct setup_data *) boot_params->hdr.setup_data;
> +	while (data) {
> +		if (data->type == SETUP_EFI)
> +			return true;
> +		data = (struct setup_data *) data->next;
> +	}
> +
> +	return false;
> +}
> +
>  /* Search EFI system tables for RSDP. */
>  static acpi_physical_address efi_get_rsdp_addr(void)
>  {
> @@ -57,6 +75,10 @@ static acpi_physical_address efi_get_rsdp_addr(void)
>  	int size, i;
>  	char *sig;
>  
> +	/* If the system is kexec-booted, poking EFI systab may not work. */
> +	if (is_kexec_booted())
> +		return 0;
> +
>  	ei = &boot_params->efi_info;
>  	sig = (char *)&ei->efi_loader_signature;
>  
> 
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Good catch, this way looks good to me.  But the function
is_kexec_booted can be compiled when #ifdef CONFIG_EFI

Otherwise:

Acked-by: Dave Young <dyoung@...hat.com>

Thanks
Dave

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