Re: [PATCH v3 04/11] KVM: page track: add the framework of guest page tracking

[Paolo Bonzini]

On 14/02/2016 12:31, Xiao Guangrong wrote:
> The array, gfn_track[mode][gfn], is introduced in memory slot for every
> guest page, this is the tracking count for the gust page on different
> modes. If the page is tracked then the count is increased, the page is
> not tracked after the count reaches zero
> 
> We use 'unsigned short' as the tracking count which should be enough as
> shadow page table only can use 2^14 (2^3 for level, 2^1 for cr4_pae, 2^2
> for quadrant, 2^3 for access, 2^1 for nxe, 2^1 for cr0_wp, 2^1 for
> smep_andnot_wp, 2^1 for smap_andnot_wp, and 2^1 for smm) at most, there
> is enough room for other trackers
> 
> Two callbacks, kvm_page_track_create_memslot() and
> kvm_page_track_free_memslot() are implemented in this patch, they are
> internally used to initialize and reclaim the memory of the array
> 
> Currently, only write track mode is supported
> 
> Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm_host.h       |  2 ++
>  arch/x86/include/asm/kvm_page_track.h | 13 +++++++++
>  arch/x86/kvm/Makefile                 |  3 +-
>  arch/x86/kvm/page_track.c             | 52 +++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/x86.c                    |  5 ++++
>  5 files changed, 74 insertions(+), 1 deletion(-)
>  create mode 100644 arch/x86/include/asm/kvm_page_track.h
>  create mode 100644 arch/x86/kvm/page_track.c
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e1c1f57..d8931d0 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -32,6 +32,7 @@
>  #include <asm/mtrr.h>
>  #include <asm/msr-index.h>
>  #include <asm/asm.h>
> +#include <asm/kvm_page_track.h>
>  
>  #define KVM_MAX_VCPUS 255
>  #define KVM_SOFT_MAX_VCPUS 160
> @@ -650,6 +651,7 @@ struct kvm_lpage_info {
>  struct kvm_arch_memory_slot {
>  	struct kvm_rmap_head *rmap[KVM_NR_PAGE_SIZES];
>  	struct kvm_lpage_info *lpage_info[KVM_NR_PAGE_SIZES - 1];
> +	unsigned short *gfn_track[KVM_PAGE_TRACK_MAX];

Please add a comment at struct kvm_mmu_page_role mentioning that the
number of role bits for shadow pages (i.e. not counting direct and
invalid) must not exceed 15 (16 thoretically risks overflow already!),
and counting the 14 bits that are in use.

Paolo

>  };
>  
>  /*
> diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
> new file mode 100644
> index 0000000..55200406
> --- /dev/null
> +++ b/arch/x86/include/asm/kvm_page_track.h
> @@ -0,0 +1,13 @@
> +#ifndef _ASM_X86_KVM_PAGE_TRACK_H
> +#define _ASM_X86_KVM_PAGE_TRACK_H
> +
> +enum kvm_page_track_mode {
> +	KVM_PAGE_TRACK_WRITE,
> +	KVM_PAGE_TRACK_MAX,
> +};
> +
> +void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
> +				 struct kvm_memory_slot *dont);
> +int kvm_page_track_create_memslot(struct kvm_memory_slot *slot,
> +				  unsigned long npages);
> +#endif
> diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
> index a1ff508..464fa47 100644
> --- a/arch/x86/kvm/Makefile
> +++ b/arch/x86/kvm/Makefile
> @@ -13,9 +13,10 @@ kvm-$(CONFIG_KVM_ASYNC_PF)	+= $(KVM)/async_pf.o
>  
>  kvm-y			+= x86.o mmu.o emulate.o i8259.o irq.o lapic.o \
>  			   i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \
> -			   hyperv.o
> +			   hyperv.o page_track.o
>  
>  kvm-$(CONFIG_KVM_DEVICE_ASSIGNMENT)	+= assigned-dev.o iommu.o
> +
>  kvm-intel-y		+= vmx.o pmu_intel.o
>  kvm-amd-y		+= svm.o pmu_amd.o
>  
> diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c
> new file mode 100644
> index 0000000..8c396d0
> --- /dev/null
> +++ b/arch/x86/kvm/page_track.c
> @@ -0,0 +1,52 @@
> +/*
> + * Support KVM gust page tracking
> + *
> + * This feature allows us to track page access in guest. Currently, only
> + * write access is tracked.
> + *
> + * Copyright(C) 2015 Intel Corporation.
> + *
> + * Author:
> + *   Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + */
> +
> +#include <linux/kvm_host.h>
> +#include <asm/kvm_host.h>
> +#include <asm/kvm_page_track.h>
> +
> +#include "mmu.h"
> +
> +void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
> +				 struct kvm_memory_slot *dont)
> +{
> +	int i;
> +
> +	for (i = 0; i < KVM_PAGE_TRACK_MAX; i++)
> +		if (!dont || free->arch.gfn_track[i] !=
> +		      dont->arch.gfn_track[i]) {
> +			kvfree(free->arch.gfn_track[i]);
> +			free->arch.gfn_track[i] = NULL;
> +		}
> +}
> +
> +int kvm_page_track_create_memslot(struct kvm_memory_slot *slot,
> +				  unsigned long npages)
> +{
> +	int  i;
> +
> +	for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) {
> +		slot->arch.gfn_track[i] = kvm_kvzalloc(npages *
> +					    sizeof(*slot->arch.gfn_track[i]));
> +		if (!slot->arch.gfn_track[i])
> +			goto track_free;
> +	}
> +
> +	return 0;
> +
> +track_free:
> +	kvm_page_track_free_memslot(slot, NULL);
> +	return -ENOMEM;
> +}
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f448e64..e25ebb7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7895,6 +7895,8 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
>  			free->arch.lpage_info[i - 1] = NULL;
>  		}
>  	}
> +
> +	kvm_page_track_free_memslot(free, dont);
>  }
>  
>  int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
> @@ -7943,6 +7945,9 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
>  		}
>  	}
>  
> +	if (kvm_page_track_create_memslot(slot, npages))
> +		goto out_free;
> +
>  	return 0;
>  
>  out_free:
>