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SubjectRe: [Xen-devel] [PATCH] xen pv-on-hvm: add pfn_is_ram helper for kdump
On Thu, Jul 12, 2012 at 07:20:39PM +0200, Olaf Hering wrote:
> Register pfn_is_ram helper speed up reading /proc/vmcore in the kdump
> kernel. See commit message of 997c136f518c ("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: Olaf Hering <olaf@aepfle.de>
> ---
> arch/x86/xen/mmu.c | 41 ++++++++++++++++++++++++++++++++++++
> include/xen/interface/hvm/hvm_op.h | 20 ++++++++++++++++++
> 2 Dateien geändert, 61 Zeilen hinzugefügt(+)
>
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index 3a73785..54de84d 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -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>
>
> @@ -2245,6 +2246,43 @@ 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;
> @@ -2275,6 +2313,9 @@ 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
>
> diff --git a/include/xen/interface/hvm/hvm_op.h b/include/xen/interface/hvm/hvm_op.h
> index a4827f4..0816ae4 100644
> --- a/include/xen/interface/hvm/hvm_op.h
> +++ b/include/xen/interface/hvm/hvm_op.h
> @@ -43,4 +43,24 @@ 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);
>
> +typedef enum {
> + 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 */
> +} hvmmem_type_t;

Does this have to be a typdef?

> +
> +#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;
> +};
> +typedef struct xen_hvm_get_mem_type xen_hvm_get_mem_type_t;

Please no typdefs. I can fix this up, but in the future pls don't add
more of them.


> +DEFINE_GUEST_HANDLE_STRUCT(xen_hvm_get_mem_type_t);
> +
> #endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */
> --
> 1.7.10.4
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel
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