> -----Original Message-----
> From: Alexandru Stefan ISAILA [mailto:aisa...@bitdefender.com]
> Sent: 04 June 2019 12:50
> To: xen-devel@lists.xenproject.org
> Cc: Paul Durrant <paul.durr...@citrix.com>; jbeul...@suse.com; Andrew Cooper
> <andrew.coop...@citrix.com>; w...@xen.org; Roger Pau Monne
> <roger....@citrix.com>;
> boris.ostrov...@oracle.com; suravee.suthikulpa...@amd.com;
> brian.wo...@amd.com;
> rcojoc...@bitdefender.com; ta...@tklengyel.com; jun.nakaj...@intel.com; Kevin
> Tian
> <kevin.t...@intel.com>; George Dunlap <george.dun...@citrix.com>; Tim
> (Xen.org) <t...@xen.org>;
> Alexandru Stefan ISAILA <aisa...@bitdefender.com>
> Subject: [PATCH v5] x86/emulate: Send vm_event from emulate
>
> This patch aims to have mem access vm events sent from the emulator.
> This is useful where we want to only emulate a page walk without
> checking the EPT, but we still want to check the EPT when emulating
> the instruction that caused the page walk. In this case, the original
> EPT fault is caused by the walk trying to set the accessed or dirty
> bits, but executing the instruction itself might also cause an EPT
> fault if permitted to run, and this second fault should not be lost.
>
> We use hvmemul_map_linear_addr() to intercept r/w access and
> __hvm_copy() to intercept exec access.
>
> First we try to send a vm event and if the event is sent then emulation
> returns X86EMUL_RETRY in order to stop emulation on instructions that
> use access protected pages. If the event is not sent then the
> emulation goes on as expected.
>
> Signed-off-by: Alexandru Isaila <aisa...@bitdefender.com>
Emulation parts...
Reviewed-by: Paul Durrant <paul.durr...@citrix.com>
...with one nit, inline below...
>
> ---
> Changes since V4:
> - Move the exec interception to __hvm_copy()
> - Remove the page-walk in hvm_emulate_send_vm_event() and get
> the needed address from the existing page walk
> - Add send_event param to __hvm_copy() and
> hvm_copy_from_guest_linear()
> - Drop X86EMUL_ACCESS_EXCEPTION and use X86EMUL_RETRY instead.
> ---
> xen/arch/x86/hvm/emulate.c | 71 +++++++++++++++++++++++++++++--
> xen/arch/x86/hvm/hvm.c | 27 +++++++-----
> xen/arch/x86/hvm/svm/svm.c | 2 +-
> xen/arch/x86/hvm/vm_event.c | 2 +-
> xen/arch/x86/hvm/vmx/vvmx.c | 2 +-
> xen/arch/x86/mm/mem_access.c | 3 +-
> xen/arch/x86/mm/shadow/common.c | 4 +-
> xen/arch/x86/mm/shadow/hvm.c | 2 +-
> xen/include/asm-x86/hvm/emulate.h | 9 +++-
> xen/include/asm-x86/hvm/support.h | 2 +-
> 10 files changed, 101 insertions(+), 23 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
> index 8659c89862..9b2d8c2014 100644
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -12,9 +12,11 @@
> #include <xen/init.h>
> #include <xen/lib.h>
> #include <xen/sched.h>
> +#include <xen/monitor.h>
> #include <xen/paging.h>
> #include <xen/trace.h>
> #include <xen/vm_event.h>
> +#include <asm/altp2m.h>
> #include <asm/event.h>
> #include <asm/i387.h>
> #include <asm/xstate.h>
> @@ -530,6 +532,57 @@ static int hvmemul_do_mmio_addr(paddr_t mmio_gpa,
> return hvmemul_do_io_addr(1, mmio_gpa, reps, size, dir, df, ram_gpa);
> }
>
> +bool hvm_emulate_send_vm_event(unsigned long gla, gfn_t gfn,
> + uint32_t pfec, bool send_event)
> +{
> + xenmem_access_t access;
> + vm_event_request_t req = {};
> + paddr_t gpa = ((gfn_x(gfn) << PAGE_SHIFT) | (gla & ~PAGE_MASK));
> +
> + if ( !send_event || !pfec )
> + return false;
> +
> + if ( p2m_get_mem_access(current->domain, gfn, &access,
> + altp2m_vcpu_idx(current)) != 0 )
> + return false;
> +
> + switch ( access ) {
> + case XENMEM_access_x:
> + case XENMEM_access_rx:
> + if ( pfec & PFEC_write_access )
> + req.u.mem_access.flags = MEM_ACCESS_R | MEM_ACCESS_W;
> + break;
> +
> + case XENMEM_access_w:
> + case XENMEM_access_rw:
> + if ( pfec & PFEC_insn_fetch )
> + req.u.mem_access.flags = MEM_ACCESS_X;
> + break;
> +
> + case XENMEM_access_r:
> + case XENMEM_access_n:
> + if ( pfec & PFEC_write_access )
> + req.u.mem_access.flags |= MEM_ACCESS_R | MEM_ACCESS_W;
> + if ( pfec & PFEC_insn_fetch )
> + req.u.mem_access.flags |= MEM_ACCESS_X;
> + break;
> +
> + default:
> + return false;
> + }
> +
> + if ( !req.u.mem_access.flags )
> + return false; /* no violation */
> +
> + req.reason = VM_EVENT_REASON_MEM_ACCESS;
> + req.u.mem_access.gfn = gfn_x(gfn);
> + req.u.mem_access.flags |= MEM_ACCESS_FAULT_WITH_GLA |
> MEM_ACCESS_GLA_VALID;
> + req.u.mem_access.gla = gla;
> + req.u.mem_access.offset = gpa & ((1 << PAGE_SHIFT) - 1);
& ~PAGE_MASK?
> +
> + return monitor_traps(current, true, &req) >= 0;
> +}
> +
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