Re: [Xen-devel] [PATCH] x86/xen: do not identity map E820 memory regions that are UNUSABLE

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On 09/07/13 19:36, Konrad Rzeszutek Wilk wrote:
> On Tue, Jul 09, 2013 at 06:00:17PM +0100, Aurelien Chartier wrote:
>> On 09/07/13 14:38, David Vrabel wrote:
>>> From: David Vrabel <david.vrabel@xxxxxxxxxx>
>>>
>>> If there are UNUSABLE regions in the machine memory map, dom0 will
>>> attempt to map them 1:1 which is not permitted by Xen and the kernel
>>> will crash.
>>>
>>> There isn't anything interesting in the UNUSABLE region that the dom0
>>> kernel needs access to so we can avoid making the 1:1 mapping and
>>> leave the region as RAM.
>>>
>>> Since the obtaining the memory map for dom0 and domU are now more
>>> different, refactor each into separate functions.
>>>
>>> This fixes a dom0 boot failure if tboot is used (because tboot was
>>> marking a memory region as UNUSABLE).
>>>
>>> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
>>> Cc: stable@xxxxxxxxxxxxxxx
>> I tested it with Xen 4.1.3-rc and Linux 3.8.13.4 and it is fixing the
>> early boot crash I reported.
> How did you test it? How can one reproduce this crash? Do you see
> this failure with v3.10 or just with v3.8 (and earlier)?

I tested it by booting Xen and Linux over tboot (1.7.0) with TXT/TPM
enabled. The issue is always reproducible.

I posted a log of the kernel panic on xen-devel in May if than can help:
http://lists.xen.org/archives/html/xen-devel/2013-05/msg01534.html

I did not test with v3.10 yet, but I did not see any commit that could
have fixed it. I'll give it a try though.

>> Tested-by: Aurelien Chartier <aurelien.chartier@xxxxxxxxxx>
>>
>>> ---
>>>  arch/x86/xen/setup.c |  114 ++++++++++++++++++++++++++++++++++++++++----------
>>>  1 files changed, 91 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
>>> index 94eac5c..3fdb6bd 100644
>>> --- a/arch/x86/xen/setup.c
>>> +++ b/arch/x86/xen/setup.c
>>> @@ -55,6 +55,91 @@ unsigned long xen_released_pages;
>>>   */
>>>  #define EXTRA_MEM_RATIO		(10)
>>>  
>>> +static int __init xen_get_memory_map_dom0(struct e820entry *map,
>>> +					  unsigned *nr_entries)
>>> +{
>>> +	struct xen_memory_map memmap;
>>> +	unsigned i;
>>> +	int ret;
>>> +
>>> +	/*
>>> +	 * Dom0 requires access to machine addresses for BIOS data and
>>> +	 * MMIO (e.g. PCI) devices.  The reset of the kernel expects
>>> +	 * to be able to access these through a 1:1 p2m mapping.
>>> +	 *
>>> +	 * We need to take the pseudo physical memory map and set up
>>> +	 * 1:1 mappings corresponding to the RESERVED regions and
>>> +	 * holes in the /machine/ memory map, adding/expanding the RAM
>>> +	 * region at the end of the map for the relocated RAM.
>>> +	 *
>>> +	 * This is more easily done if we just start with the machine
>>> +	 * memory map.
>>> +	 *
>>> +	 * UNUSABLE regions are awkward, they are not interesting to
>>> +	 * dom0 and Xen won't allow them to be mapped so we want to
>>> +	 * leave these as RAM in the pseudo physical map.
>>> +	 *
>>> +	 * Again, this is easiest if we take the machine memory map
>>> +	 * and change the UNUSABLE regions to RAM.
>>> +	 */
>>> +
>>> +	memmap.nr_entries = *nr_entries;
>>> +	set_xen_guest_handle(memmap.buffer, map);
>>> +
>>> +	ret = HYPERVISOR_memory_op(XENMEM_machine_memory_map, &memmap);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	for (i = 0; i < memmap.nr_entries; i++) {
>>> +		if (map[i].type == E820_UNUSABLE)
>>> +			map[i].type = E820_RAM;
>>> +	}
>>> +
>>> +	*nr_entries = memmap.nr_entries;
>>> +	return 0;
>>> +}
>>> +
>>> +static int __init xen_get_memory_map_domu(struct e820entry *map,
>>> +					  unsigned *nr_entries)
>>> +{
>>> +	struct xen_memory_map memmap;
>>> +	int ret;
>>> +
>>> +	/*
>>> +	 * For domUs, use the psuedo-physical memory map.
>> Small typo here.
>>
>>> +	 *
>>> +	 * If this is not available, fake up a memory map with a
>>> +	 * single region containing the initial number of pages.
>>> +	 */
>>> +
>>> +	memmap.nr_entries = *nr_entries;
>>> +	set_xen_guest_handle(memmap.buffer, map);
>>> +
>>> +	ret = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
>>> +	if (ret == -ENOSYS) {
>>> +		unsigned long max_pfn = min(MAX_DOMAIN_PAGES,
>>> +					    xen_start_info->nr_pages);
>>> +		memmap.nr_entries = 1;
>>> +		map[0].addr = 0ULL;
>>> +		map[0].size = PFN_PHYS(max_pfn);
>>> +		/* 8MB slack (to balance backend allocations). */
>>> +		map[0].size += 8ULL << 20;
>>> +		map[0].type = E820_RAM;
>>> +	} else if (ret < 0)
>>> +		return ret;
>>> +
>>> +	*nr_entries = memmap.nr_entries;
>>> +	return 0;
>>> +}
>>> +
>>> +static int __init xen_get_memory_map(struct e820entry *map, unsigned *nr_entries)
>>> +{
>>> +	if (xen_initial_domain())
>>> +		return xen_get_memory_map_dom0(map, nr_entries);
>>> +	else
>>> +		return xen_get_memory_map_domu(map, nr_entries);
>>> +}
>>> +
>>>  static void __init xen_add_extra_mem(u64 start, u64 size)
>>>  {
>>>  	unsigned long pfn;
>>> @@ -319,42 +404,25 @@ static void xen_align_and_add_e820_region(u64 start, u64 size, int type)
>>>  char * __init xen_memory_setup(void)
>>>  {
>>>  	static struct e820entry map[E820MAX] __initdata;
>>> +	unsigned map_nr_entries = E820MAX;
>>>  
>>>  	unsigned long max_pfn = xen_start_info->nr_pages;
>>>  	unsigned long long mem_end;
>>>  	int rc;
>>> -	struct xen_memory_map memmap;
>>>  	unsigned long max_pages;
>>>  	unsigned long last_pfn = 0;
>>>  	unsigned long extra_pages = 0;
>>>  	unsigned long populated;
>>>  	int i;
>>> -	int op;
>>>  
>>>  	max_pfn = min(MAX_DOMAIN_PAGES, max_pfn);
>>>  	mem_end = PFN_PHYS(max_pfn);
>>>  
>>> -	memmap.nr_entries = E820MAX;
>>> -	set_xen_guest_handle(memmap.buffer, map);
>>> -
>>> -	op = xen_initial_domain() ?
>>> -		XENMEM_machine_memory_map :
>>> -		XENMEM_memory_map;
>>> -	rc = HYPERVISOR_memory_op(op, &memmap);
>>> -	if (rc == -ENOSYS) {
>>> -		BUG_ON(xen_initial_domain());
>>> -		memmap.nr_entries = 1;
>>> -		map[0].addr = 0ULL;
>>> -		map[0].size = mem_end;
>>> -		/* 8MB slack (to balance backend allocations). */
>>> -		map[0].size += 8ULL << 20;
>>> -		map[0].type = E820_RAM;
>>> -		rc = 0;
>>> -	}
>>> +	rc = xen_get_memory_map(map, &map_nr_entries);
>>>  	BUG_ON(rc);
>>>  
>>>  	/* Make sure the Xen-supplied memory map is well-ordered. */
>>> -	sanitize_e820_map(map, memmap.nr_entries, &memmap.nr_entries);
>>> +	sanitize_e820_map(map, map_nr_entries, &map_nr_entries);
>>>  
>>>  	max_pages = xen_get_max_pages();
>>>  	if (max_pages > max_pfn)
>>> @@ -366,12 +434,12 @@ char * __init xen_memory_setup(void)
>>>  	 * this are first released.
>>>  	 */
>>>  	xen_released_pages = xen_set_identity_and_release(
>>> -		map, memmap.nr_entries, max_pfn);
>>> +		map, map_nr_entries, max_pfn);
>>>  
>>>  	/*
>>>  	 * Populate back the non-RAM pages and E820 gaps that had been
>>>  	 * released. */
>>> -	populated = xen_populate_chunk(map, memmap.nr_entries,
>>> +	populated = xen_populate_chunk(map, map_nr_entries,
>>>  			max_pfn, &last_pfn, xen_released_pages);
>>>  
>>>  	xen_released_pages -= populated;
>>> @@ -395,7 +463,7 @@ char * __init xen_memory_setup(void)
>>>  	extra_pages = min(EXTRA_MEM_RATIO * min(max_pfn, PFN_DOWN(MAXMEM)),
>>>  			  extra_pages);
>>>  	i = 0;
>>> -	while (i < memmap.nr_entries) {
>>> +	while (i < map_nr_entries) {
>>>  		u64 addr = map[i].addr;
>>>  		u64 size = map[i].size;
>>>  		u32 type = map[i].type;
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel

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