linux-kernel - Re: [PATCH v2] x86/boot: Use EFI setup data if provided

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Message-ID: <20190327014852.GA3659@MiWiFi-R3L-srv>
Date:   Wed, 27 Mar 2019 09:48:52 +0800
From:   "bhe@...hat.com" <bhe@...hat.com>
To:     Junichi Nomura <j-nomura@...jp.nec.com>,
        Borislav Petkov <bp@...en8.de>
Cc:     Dave Young <dyoung@...hat.com>,
        "fanc.fnst@...fujitsu.com" <fanc.fnst@...fujitsu.com>,
        "kasong@...hat.com" <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86/boot: Use EFI setup data if provided

Hi Junichi,

On 03/26/19 at 02:57pm, Borislav Petkov wrote:
> On Mon, Mar 25, 2019 at 11:10:01PM +0000, Junichi Nomura wrote:
> > efi_get_rsdp_addr() and kexec_get_rsdp_addr() could be implemented
> > like this (sorry about the pseudo code):
> 
> This doesn't look like what I suggested:
> 
> > So efi_get_rsdp_addr() needs to be refactored in such a way so that at
> > least the loop towards the end gets carved out into a separate function
> > - __efi_get_rsdp_addr() or so - which gets config_tables, nr_tables and
> > size as arguments and finds the RSDP address in the kexec-ed kernel.
> 
> You need to carve out the loop at the end and make it into a separate
> __efi_get_rsdp_addr() function which gets the physical or the virtual
> address.

I guess Boris is suggesting code like below. Please correct me if I am
wrong.

static acpi_physical_address _efi_get_rsdp_addr(efi_config_table tbl, ...)
{
	/* Get EFI tables from systab. */
	for (i = 0; i < nr_tables; i++) {
		...
	}
	return rsdp_addr;
}

static acpi_physical_address efi_get_rsdp_addr(void)
{
	...
	/* Get systab from boot params. */		
	...
	/* Handle EFI bitness properly */
	...
	return _efi_get_rsdp_addr();
}


static acpi_physical_address kexec_get_rsdp_addr(void)
{
	if (!is_kexec_booted)
		return 0;

	efi_get_setup_data_addr();
	...
	/* Handle EFI bitness properly */
	...
	return _efi_get_rsdp_addr();
}

acpi_physical_address get_rsdp_addr(void)
{
        acpi_physical_address pa;

        pa = get_acpi_rsdp();

        if (!pa)
                pa = boot_params->acpi_rsdp_addr;


	/**
	/*I think here we should check if it's kexec booted firstly.
	 * Skip it if not kexec. this can avoid the wrong kexec virt
	 * addr parsing./
        if (!pa)
                pa = kexec_get_rdsp_addr();             <--- new function

        if (!pa)
                pa = efi_get_rsdp_addr();

        if (!pa)
                pa = bios_get_rsdp_addr();

        return pa;
}