Commit 34b6f01a authored by Olaf Hering's avatar Olaf Hering Committed by Konrad Rzeszutek Wilk
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xen pv-on-hvm: add pfn_is_ram helper for kdump 



Register pfn_is_ram helper speed up reading /proc/vmcore in the kdump
kernel. See commit message of 997c136f ("fs/proc/vmcore.c: add hook
to read_from_oldmem() to check for non-ram pages") for details.

It makes use of a new hvmop HVMOP_get_mem_type which was introduced in
xen 4.2 (23298:26413986e6e0) and backported to 4.1.1.

The new function is currently only enabled for reading /proc/vmcore.
Later it will be used also for the kexec kernel. Since that requires
more changes in the generic kernel make it static for the time being.

Signed-off-by: default avatarOlaf Hering <olaf@aepfle.de>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 9b6934a3

arch/x86/xen/mmu.c

+41 −0
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ 
#include <linux/gfp.h>

#include <linux/memblock.h>

#include <linux/seq_file.h>

#include <linux/crash_dump.h>



#include <trace/events/xen.h>
@@ -2381,6 +2382,43 @@ void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order) 
EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);



#ifdef CONFIG_XEN_PVHVM

#ifdef CONFIG_PROC_VMCORE

/*

 * This function is used in two contexts:

 * - the kdump kernel has to check whether a pfn of the crashed kernel

 *   was a ballooned page. vmcore is using this function to decide

 *   whether to access a pfn of the crashed kernel.

 * - the kexec kernel has to check whether a pfn was ballooned by the

 *   previous kernel. If the pfn is ballooned, handle it properly.

 * Returns 0 if the pfn is not backed by a RAM page, the caller may

 * handle the pfn special in this case.

 */

static int xen_oldmem_pfn_is_ram(unsigned long pfn)

{

	struct xen_hvm_get_mem_type a = {

		.domid = DOMID_SELF,

		.pfn = pfn,

	};

	int ram;



	if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a))

		return -ENXIO;



	switch (a.mem_type) {

		case HVMMEM_mmio_dm:

			ram = 0;

			break;

		case HVMMEM_ram_rw:

		case HVMMEM_ram_ro:

		default:

			ram = 1;

			break;

	}



	return ram;

}

#endif



static void xen_hvm_exit_mmap(struct mm_struct *mm)

{

	struct xen_hvm_pagetable_dying a;
@@ -2411,6 +2449,9 @@ void __init xen_hvm_init_mmu_ops(void) 
{

	if (is_pagetable_dying_supported())

		pv_mmu_ops.exit_mmap = xen_hvm_exit_mmap;

#ifdef CONFIG_PROC_VMCORE

	register_oldmem_pfn_is_ram(&xen_oldmem_pfn_is_ram);

#endif

}

#endif

include/xen/interface/hvm/hvm_op.h

+19 −0
Original line number Diff line number Diff line
@@ -43,4 +43,23 @@ struct xen_hvm_pagetable_dying { 
typedef struct xen_hvm_pagetable_dying xen_hvm_pagetable_dying_t;

DEFINE_GUEST_HANDLE_STRUCT(xen_hvm_pagetable_dying_t);

 

enum hvmmem_type_t {

    HVMMEM_ram_rw,             /* Normal read/write guest RAM */

    HVMMEM_ram_ro,             /* Read-only; writes are discarded */

    HVMMEM_mmio_dm,            /* Reads and write go to the device model */

};



#define HVMOP_get_mem_type    15

/* Return hvmmem_type_t for the specified pfn. */

struct xen_hvm_get_mem_type {

    /* Domain to be queried. */

    domid_t domid;

    /* OUT variable. */

    uint16_t mem_type;

    uint16_t pad[2]; /* align next field on 8-byte boundary */

    /* IN variable. */

    uint64_t pfn;

};

DEFINE_GUEST_HANDLE_STRUCT(xen_hvm_get_mem_type);



#endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */

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