linux-kernel - Re: [PATCH v3 5/5] xen: Put EFI machinery in place

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Date:	Wed, 26 Mar 2014 13:31:04 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Matt Fleming" <matt@...sole-pimps.org>
Cc:	<david.vrabel@...rix.com>, <ian.campbell@...rix.com>,
	<stefano.stabellini@...citrix.com>, <jeremy@...p.org>,
	<fenghua.yu@...el.com>, <matt.fleming@...el.com>,
	<tony.luck@...el.com>, <x86@...nel.org>, <tglx@...utronix.de>,
	<xen-devel@...ts.xenproject.org>, <boris.ostrovsky@...cle.com>,
	"Daniel Kiper" <daniel.kiper@...cle.com>, <konrad.wilk@...cle.com>,
	"Tang Liang" <liang.tang@...cle.com>, <eshelton@...ox.com>,
	<mingo@...hat.com>, <linux-efi@...r.kernel.org>,
	<linux-ia64@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<hpa@...or.com>
Subject: Re: [PATCH v3 5/5] xen: Put EFI machinery in place

>>> On 26.03.14 at 14:12, <matt@...sole-pimps.org> wrote:
> On Tue, 25 Mar, at 09:57:56PM, Daniel Kiper wrote:
>> +static void __init efi_init_xen(void)
>> +{
>> +	efi_char16_t vendor_c16[100];
>> +	char vendor[ARRAY_SIZE(vendor_c16)];
>> +	int ret, i;
>> +	struct xen_platform_op op;
>> +	union xenpf_efi_info *info = &op.u.firmware_info.u.efi_info;
>> +
>> +	efi = efi_xen;
>> +	op.cmd = XENPF_firmware_info;
>> +	op.u.firmware_info.type = XEN_FW_EFI_INFO;
>> +
>> +	/*
>> +	 * Show what we know for posterity
>> +	 */
>> +	op.u.firmware_info.index = XEN_FW_EFI_VENDOR;
>> +	info->vendor.bufsz = sizeof(vendor_c16);
>> +	set_xen_guest_handle(info->vendor.name, vendor_c16);
>> +	ret = HYPERVISOR_dom0_op(&op);
>> +	if (!ret) {
>> +		for (i = 0; i < sizeof(vendor) - 1 && vendor_c16[i]; ++i)
>> +			vendor[i] = vendor_c16[i];
>> +		vendor[i] = '\0';
>> +	} else
>> +		pr_err("Could not get the firmware vendor!\n");
>> +
> 
> Is there a reason that you can't just populate an efi_system_table_t
> object, which could be used by efi_init(), so that we can save you the
> trouble of duplicating all of this code?

Would the generic function cope with all other fields being NULL (or
equivalent)?

>> +/*
>> + * Convenience functions to obtain memory types and attributes
>> + */
>> +static u32 efi_mem_type_xen(unsigned long phys_addr)
>> +{
>> +	struct xen_platform_op op;
>> +	union xenpf_efi_info *info = &op.u.firmware_info.u.efi_info;
>> +
>> +	op.cmd = XENPF_firmware_info;
>> +	op.u.firmware_info.type = XEN_FW_EFI_INFO;
>> +	op.u.firmware_info.index = XEN_FW_EFI_MEM_INFO;
>> +	info->mem.addr = phys_addr;
>> +	info->mem.size = 0;
>> +	return HYPERVISOR_dom0_op(&op) ? 0 : info->mem.type;
>> +}
> 
> Same idea here. Unless you expect the EFI memory map to change at runtime
> (and it's not clear to me whether that wouldn't cause other things to
> explode) you'd be better off building a struct efi_memory_map and using
> the existing generic functions.

As said in another reply to this series - the memory map isn't being
(and shouldn't be) exposed to Dom0.

Jan

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