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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v6] x86/mm: Suppresses vm_events caused by page-walks
On Mon, May 7, 2018 at 7:40 AM, Alexandru Isaila
<aisaila@xxxxxxxxxxxxxxx> wrote:
> This patch is adding a way to enable/disable inguest pagefault
> events. It introduces the xc_monitor_inguest_pagefault function
> and adds the inguest_pagefault_disabled in the monitor structure.
> This is needed by the introspection so it will only get gla
> faults and not get spammed with other faults.
> In p2m_mem_access_check() we emulate so no event will get sent.
Thanks for the changes!
Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
>
> ---
> Changes since V5:
> - Add comment for the xc_monitor_inguest_pagefault() func.
> - Add altp2m_write_no_gpt test in xen_access
> ---
> tools/libxc/include/xenctrl.h | 7 +++++++
> tools/libxc/xc_monitor.c | 14 ++++++++++++++
> tools/tests/xen-access/xen-access.c | 36 +++++++++++++++++++++++++++++++++++-
> xen/arch/x86/mm/mem_access.c | 9 +++++++++
> xen/arch/x86/monitor.c | 13 +++++++++++++
> xen/include/asm-x86/domain.h | 5 +++++
> xen/include/asm-x86/monitor.h | 3 ++-
> xen/include/public/domctl.h | 2 ++
> 8 files changed, 87 insertions(+), 2 deletions(-)
>
> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
> index 09e1363..6f9070d 100644
> --- a/tools/libxc/include/xenctrl.h
> +++ b/tools/libxc/include/xenctrl.h
> @@ -2056,6 +2056,13 @@ int xc_monitor_descriptor_access(xc_interface *xch,
> uint32_t domain_id,
> bool enable);
> int xc_monitor_guest_request(xc_interface *xch, uint32_t domain_id,
> bool enable, bool sync, bool allow_userspace);
> +/*
> + * Disables page-walk mem_access events by emulating. If the
> + * emulation can not be performed then a VM_EVENT_REASON_EMUL_UNIMPLEMENTED
> + * event will be issued.
> + */
> +int xc_monitor_inguest_pagefault(xc_interface *xch, uint32_t domain_id,
> + bool disable);
> int xc_monitor_debug_exceptions(xc_interface *xch, uint32_t domain_id,
> bool enable, bool sync);
> int xc_monitor_cpuid(xc_interface *xch, uint32_t domain_id, bool enable);
> diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
> index 0233b87..4ac823e 100644
> --- a/tools/libxc/xc_monitor.c
> +++ b/tools/libxc/xc_monitor.c
> @@ -163,6 +163,20 @@ int xc_monitor_guest_request(xc_interface *xch, uint32_t
> domain_id, bool enable,
> return do_domctl(xch, &domctl);
> }
>
> +int xc_monitor_inguest_pagefault(xc_interface *xch, uint32_t domain_id,
> + bool disable)
> +{
> + DECLARE_DOMCTL;
> +
> + domctl.cmd = XEN_DOMCTL_monitor_op;
> + domctl.domain = domain_id;
> + domctl.u.monitor_op.op = disable ? XEN_DOMCTL_MONITOR_OP_ENABLE
> + : XEN_DOMCTL_MONITOR_OP_DISABLE;
> + domctl.u.monitor_op.event = XEN_DOMCTL_MONITOR_EVENT_INGUEST_PAGEFAULT;
> +
> + return do_domctl(xch, &domctl);
> +}
> +
> int xc_monitor_emulate_each_rep(xc_interface *xch, uint32_t domain_id,
> bool enable)
> {
> diff --git a/tools/tests/xen-access/xen-access.c
> b/tools/tests/xen-access/xen-access.c
> index 9d960e2..e940137 100644
> --- a/tools/tests/xen-access/xen-access.c
> +++ b/tools/tests/xen-access/xen-access.c
> @@ -362,7 +362,7 @@ void usage(char* progname)
> {
> fprintf(stderr, "Usage: %s [-m] <domain_id> write|exec", progname);
> #if defined(__i386__) || defined(__x86_64__)
> - fprintf(stderr,
> "|breakpoint|altp2m_write|altp2m_exec|debug|cpuid|desc_access|write_ctrlreg_cr4");
> + fprintf(stderr,
> "|breakpoint|altp2m_write|altp2m_exec|debug|cpuid|desc_access|write_ctrlreg_cr4|altp2m_write_no_gpt");
> #elif defined(__arm__) || defined(__aarch64__)
> fprintf(stderr, "|privcall");
> #endif
> @@ -395,6 +395,7 @@ int main(int argc, char *argv[])
> int cpuid = 0;
> int desc_access = 0;
> int write_ctrlreg_cr4 = 0;
> + int altp2m_write_no_gpt = 0;
> uint16_t altp2m_view_id = 0;
>
> char* progname = argv[0];
> @@ -453,6 +454,13 @@ int main(int argc, char *argv[])
> altp2m = 1;
> memaccess = 1;
> }
> + else if ( !strcmp(argv[0], "altp2m_write_no_gpt") )
> + {
> + default_access = XENMEM_access_rw;
> + altp2m_write_no_gpt = 1;
> + memaccess = 1;
> + altp2m = 1;
> + }
> else if ( !strcmp(argv[0], "debug") )
> {
> debug = 1;
> @@ -513,6 +521,22 @@ int main(int argc, char *argv[])
> xen_pfn_t gfn = 0;
> unsigned long perm_set = 0;
>
> + if( altp2m_write_no_gpt )
> + {
> + rc = xc_monitor_inguest_pagefault(xch, domain_id, 1);
> + if ( rc < 0 )
> + {
> + ERROR("Error %d setting inguest pagefault\n", rc);
> + goto exit;
> + }
> + rc = xc_monitor_emul_unimplemented(xch, domain_id, 1);
> + if ( rc < 0 )
> + {
> + ERROR("Error %d failed to enable emul unimplemented\n", rc);
> + goto exit;
> + }
> + }
> +
> rc = xc_altp2m_set_domain_state( xch, domain_id, 1 );
> if ( rc < 0 )
> {
> @@ -857,6 +881,16 @@ int main(int argc, char *argv[])
> req.u.write_ctrlreg.old_value,
> req.u.write_ctrlreg.new_value);
> break;
> + case VM_EVENT_REASON_EMUL_UNIMPLEMENTED:
> + if ( altp2m_write_no_gpt && req.flags &
> VM_EVENT_FLAG_ALTERNATE_P2M )
> + {
> + DPRINTF("\tSwitching back to default view!\n");
> +
> + rsp.flags |= (VM_EVENT_FLAG_ALTERNATE_P2M |
> + VM_EVENT_FLAG_TOGGLE_SINGLESTEP);
> + rsp.altp2m_idx = 0;
> + }
> + break;
> default:
> fprintf(stderr, "UNKNOWN REASON CODE %d\n", req.reason);
> }
> diff --git a/xen/arch/x86/mm/mem_access.c b/xen/arch/x86/mm/mem_access.c
> index c0cd017..febe38d 100644
> --- a/xen/arch/x86/mm/mem_access.c
> +++ b/xen/arch/x86/mm/mem_access.c
> @@ -28,6 +28,7 @@
> #include <public/vm_event.h>
> #include <asm/p2m.h>
> #include <asm/altp2m.h>
> +#include <asm/hvm/emulate.h>
> #include <asm/vm_event.h>
>
> #include "mm-locks.h"
> @@ -207,6 +208,14 @@ bool p2m_mem_access_check(paddr_t gpa, unsigned long gla,
> return true;
> }
> }
> + if ( vm_event_check_ring(d->vm_event_monitor) &&
> + d->arch.monitor.inguest_pagefault_disabled &&
> + npfec.kind != npfec_kind_with_gla ) /* don't send a mem_event */
> + {
> + hvm_emulate_one_vm_event(EMUL_KIND_NORMAL, TRAP_invalid_op,
> X86_EVENT_NO_EC);
> +
> + return true;
> + }
>
> *req_ptr = NULL;
> req = xzalloc(vm_event_request_t);
> diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
> index f229e69..ce5d1ba 100644
> --- a/xen/arch/x86/monitor.c
> +++ b/xen/arch/x86/monitor.c
> @@ -241,6 +241,19 @@ int arch_monitor_domctl_event(struct domain *d,
> break;
> }
>
> + case XEN_DOMCTL_MONITOR_EVENT_INGUEST_PAGEFAULT:
> + {
> + bool old_status = ad->monitor.inguest_pagefault_disabled;
> +
> + if ( unlikely(old_status == requested_status) )
> + return -EEXIST;
> +
> + domain_pause(d);
> + ad->monitor.inguest_pagefault_disabled = requested_status;
> + domain_unpause(d);
> + break;
> + }
> +
> case XEN_DOMCTL_MONITOR_EVENT_DESC_ACCESS:
> {
> bool old_status = ad->monitor.descriptor_access_enabled;
> diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
> index 4679d54..fbdc392 100644
> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -412,6 +412,11 @@ struct arch_domain
> unsigned int descriptor_access_enabled :
> 1;
> unsigned int guest_request_userspace_enabled :
> 1;
> unsigned int emul_unimplemented_enabled :
> 1;
> + /*
> + * By default all events are sent.
> + * This is used to filter out pagefaults.
> + */
> + unsigned int inguest_pagefault_disabled :
> 1;
> struct monitor_msr_bitmap *msr_bitmap;
> uint64_t write_ctrlreg_mask[4];
> } monitor;
> diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
> index a0444d1..647df4a 100644
> --- a/xen/include/asm-x86/monitor.h
> +++ b/xen/include/asm-x86/monitor.h
> @@ -84,7 +84,8 @@ static inline uint32_t arch_monitor_get_capabilities(struct
> domain *d)
> (1U << XEN_DOMCTL_MONITOR_EVENT_DEBUG_EXCEPTION) |
> (1U << XEN_DOMCTL_MONITOR_EVENT_CPUID) |
> (1U << XEN_DOMCTL_MONITOR_EVENT_INTERRUPT) |
> - (1U << XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED);
> + (1U << XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED) |
> + (1U << XEN_DOMCTL_MONITOR_EVENT_INGUEST_PAGEFAULT);
>
> /* Since we know this is on VMX, we can just call the hvm func */
> if ( hvm_is_singlestep_supported() )
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index 9ae72959..ab89f35 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -1014,6 +1014,8 @@ struct xen_domctl_psr_cmt_op {
> #define XEN_DOMCTL_MONITOR_EVENT_INTERRUPT 8
> #define XEN_DOMCTL_MONITOR_EVENT_DESC_ACCESS 9
> #define XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED 10
> +/* Enabled by default */
> +#define XEN_DOMCTL_MONITOR_EVENT_INGUEST_PAGEFAULT 11
>
> struct xen_domctl_monitor_op {
> uint32_t op; /* XEN_DOMCTL_MONITOR_OP_* */
> --
> 2.7.4
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