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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v4] vm_event: Implement ARM SMC events
On Wed, 28 Sep 2016, Tamas K Lengyel wrote:
> On Wed, Sep 28, 2016 at 5:58 PM, Stefano Stabellini
> <sstabellini@xxxxxxxxxx> wrote:
> > On Fri, 16 Sep 2016, Tamas K Lengyel wrote:
> >> The ARM SMC instructions are already configured to trap to Xen by default.
> >> In
> >> this patch we allow a user-space process in a privileged domain to receive
> >> notification of when such event happens through the vm_event subsystem by
> >> introducing the PRIVILEGED_CALL type.
> >>
> >> The intended use-case for this feature is for a monitor application to be
> >> able
> >> insert tap-points into the domU kernel-code. For this task only
> >> unconditional
> >> SMC instruction should be used.
> >>
> >> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
> >> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> >> Acked-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> >> ---
> >> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> >> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> >> Cc: Julien Grall <julien.grall@xxxxxxx>
> >>
> >> v4: Style fixes
> >>
> >> Note: previous discussion around this patch proposed filtering SMCs with
> >> failed
> >> condition checks. As that patch is yet-to-be implemented and the 4.8
> >> code-freeze rapidly approaching I would like this patch to get
> >> included.
> >> In this patch a proper warning is placed in the public header for
> >> potential users not to rely on SMCs with failed condition checks
> >> being
> >> trapped. As the intended use-case for this feature doesn't use
> >> conditional SMCs this warning should be sufficient. Hardware that
> >> does
> >> issue events for SMCs with failed condition checks doesn't pose a
> >> problem
> >> for a monitor application in any way. The xen-access test tool
> >> illustrates
> >> how SMCs issued by the guest can be safely handled for all cases.
> >>
> >> tools/libxc/include/xenctrl.h | 2 +
> >> tools/libxc/xc_monitor.c | 14 +++++++
> >> tools/tests/xen-access/xen-access.c | 32 ++++++++++++++-
> >> xen/arch/arm/Makefile | 1 +
> >> xen/arch/arm/monitor.c | 80
> >> +++++++++++++++++++++++++++++++++++++
> >> xen/arch/arm/traps.c | 16 +++++++-
> >> xen/include/asm-arm/domain.h | 5 +++
> >> xen/include/asm-arm/monitor.h | 18 +++------
> >> xen/include/public/domctl.h | 1 +
> >> xen/include/public/vm_event.h | 7 ++++
> >> 10 files changed, 160 insertions(+), 16 deletions(-)
> >> create mode 100644 xen/arch/arm/monitor.c
> >>
> >> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
> >> index 560ce7b..eb53172 100644
> >> --- a/tools/libxc/include/xenctrl.h
> >> +++ b/tools/libxc/include/xenctrl.h
> >> @@ -2168,6 +2168,8 @@ int xc_monitor_guest_request(xc_interface *xch,
> >> domid_t domain_id,
> >> int xc_monitor_debug_exceptions(xc_interface *xch, domid_t domain_id,
> >> bool enable, bool sync);
> >> int xc_monitor_cpuid(xc_interface *xch, domid_t domain_id, bool enable);
> >> +int xc_monitor_privileged_call(xc_interface *xch, domid_t domain_id,
> >> + bool enable);
> >> /**
> >> * This function enables / disables emulation for each REP for a
> >> * REP-compatible instruction.
> >> diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
> >> index 4298813..15a7c32 100644
> >> --- a/tools/libxc/xc_monitor.c
> >> +++ b/tools/libxc/xc_monitor.c
> >> @@ -185,6 +185,20 @@ int xc_monitor_cpuid(xc_interface *xch, domid_t
> >> domain_id, bool enable)
> >> return do_domctl(xch, &domctl);
> >> }
> >>
> >> +int xc_monitor_privileged_call(xc_interface *xch, domid_t domain_id,
> >> + bool enable)
> >> +{
> >> + DECLARE_DOMCTL;
> >> +
> >> + domctl.cmd = XEN_DOMCTL_monitor_op;
> >> + domctl.domain = domain_id;
> >> + domctl.u.monitor_op.op = enable ? XEN_DOMCTL_MONITOR_OP_ENABLE
> >> + : XEN_DOMCTL_MONITOR_OP_DISABLE;
> >> + domctl.u.monitor_op.event = XEN_DOMCTL_MONITOR_EVENT_PRIVILEGED_CALL;
> >> +
> >> + return do_domctl(xch, &domctl);
> >> +}
> >> +
> >> /*
> >> * Local variables:
> >> * mode: C
> >> diff --git a/tools/tests/xen-access/xen-access.c
> >> b/tools/tests/xen-access/xen-access.c
> >> index ed18c71..cadeae1 100644
> >> --- a/tools/tests/xen-access/xen-access.c
> >> +++ b/tools/tests/xen-access/xen-access.c
> >> @@ -338,6 +338,8 @@ 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");
> >> +#elif defined(__arm__) || defined(__aarch64__)
> >> + fprintf(stderr, "|privcall");
> >> #endif
> >> fprintf(stderr,
> >> "\n"
> >> @@ -362,6 +364,7 @@ int main(int argc, char *argv[])
> >> int required = 0;
> >> int breakpoint = 0;
> >> int shutting_down = 0;
> >> + int privcall = 0;
> >> int altp2m = 0;
> >> int debug = 0;
> >> int cpuid = 0;
> >> @@ -431,6 +434,11 @@ int main(int argc, char *argv[])
> >> {
> >> cpuid = 1;
> >> }
> >> +#elif defined(__arm__) || defined(__aarch64__)
> >> + else if ( !strcmp(argv[0], "privcall") )
> >> + {
> >> + privcall = 1;
> >> + }
> >> #endif
> >> else
> >> {
> >> @@ -563,6 +571,16 @@ int main(int argc, char *argv[])
> >> }
> >> }
> >>
> >> + if ( privcall )
> >> + {
> >> + rc = xc_monitor_privileged_call(xch, domain_id, 1);
> >> + if ( rc < 0 )
> >> + {
> >> + ERROR("Error %d setting privileged call trapping with
> >> vm_event\n", rc);
> >> + goto exit;
> >> + }
> >> + }
> >> +
> >> /* Wait for access */
> >> for (;;)
> >> {
> >> @@ -578,6 +596,9 @@ int main(int argc, char *argv[])
> >> if ( cpuid )
> >> rc = xc_monitor_cpuid(xch, domain_id, 0);
> >>
> >> + if ( privcall )
> >> + rc = xc_monitor_privileged_call(xch, domain_id, 0);
> >> +
> >> if ( altp2m )
> >> {
> >> rc = xc_altp2m_switch_to_view( xch, domain_id, 0 );
> >> @@ -678,7 +699,7 @@ int main(int argc, char *argv[])
> >> rsp.u.mem_access = req.u.mem_access;
> >> break;
> >> case VM_EVENT_REASON_SOFTWARE_BREAKPOINT:
> >> - printf("Breakpoint: rip=%016"PRIx64", gfn=%"PRIx64" (vcpu
> >> %d)\n",
> >> + printf("Breakpoint: rip=%016"PRIx64" gfn=%"PRIx64" (vcpu
> >> %d)\n",
> >> req.data.regs.x86.rip,
> >> req.u.software_breakpoint.gfn,
> >> req.vcpu_id);
> >> @@ -695,6 +716,15 @@ int main(int argc, char *argv[])
> >> continue;
> >> }
> >> break;
> >> + case VM_EVENT_REASON_PRIVILEGED_CALL:
> >> + printf("Privileged call: pc=%"PRIx64" (vcpu %d)\n",
> >> + req.data.regs.arm.pc,
> >> + req.vcpu_id);
> >> +
> >> + rsp.data.regs.arm = req.data.regs.arm;
> >> + rsp.data.regs.arm.pc += 4;
> >> + rsp.flags |= VM_EVENT_FLAG_SET_REGISTERS;
> >> + break;
> >> case VM_EVENT_REASON_SINGLESTEP:
> >> printf("Singlestep: rip=%016"PRIx64", vcpu %d, altp2m
> >> %u\n",
> >> req.data.regs.x86.rip,
> >> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
> >> index 64fdf41..b140d7e 100644
> >> --- a/xen/arch/arm/Makefile
> >> +++ b/xen/arch/arm/Makefile
> >> @@ -25,6 +25,7 @@ obj-y += irq.o
> >> obj-y += kernel.o
> >> obj-$(CONFIG_LIVEPATCH) += livepatch.o
> >> obj-y += mm.o
> >> +obj-y += monitor.o
> >> obj-y += p2m.o
> >> obj-y += percpu.o
> >> obj-y += platform.o
> >> diff --git a/xen/arch/arm/monitor.c b/xen/arch/arm/monitor.c
> >> new file mode 100644
> >> index 0000000..1e8bdfc
> >> --- /dev/null
> >> +++ b/xen/arch/arm/monitor.c
> >> @@ -0,0 +1,80 @@
> >> +/*
> >> + * arch/arm/monitor.c
> >> + *
> >> + * Arch-specific monitor_op domctl handler.
> >> + *
> >> + * Copyright (c) 2016 Tamas K Lengyel (tamas.lengyel@xxxxxxxxxxxx)
> >> + *
> >> + * This program is free software; you can redistribute it and/or
> >> + * modify it under the terms of the GNU General Public
> >> + * License v2 as published by the Free Software Foundation.
> >> + *
> >> + * This program is distributed in the hope that it will be useful,
> >> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> >> + * General Public License for more details.
> >> + *
> >> + * You should have received a copy of the GNU General Public
> >> + * License along with this program; If not, see
> >> <http://www.gnu.org/licenses/>.
> >> + */
> >> +
> >> +#include <xen/vm_event.h>
> >> +#include <xen/monitor.h>
> >> +#include <asm/monitor.h>
> >> +#include <asm/vm_event.h>
> >> +#include <public/vm_event.h>
> >> +
> >> +int arch_monitor_domctl_event(struct domain *d,
> >> + struct xen_domctl_monitor_op *mop)
> >> +{
> >> + struct arch_domain *ad = &d->arch;
> >> + bool_t requested_status = (XEN_DOMCTL_MONITOR_OP_ENABLE == mop->op);
> >> +
> >> + switch ( mop->event )
> >> + {
> >> + case XEN_DOMCTL_MONITOR_EVENT_PRIVILEGED_CALL:
> >> + {
> >> + bool_t old_status = ad->monitor.privileged_call_enabled;
> >> +
> >> + if ( unlikely(old_status == requested_status) )
> >> + return -EEXIST;
> >> +
> >> + domain_pause(d);
> >> + ad->monitor.privileged_call_enabled = requested_status;
> >> + domain_unpause(d);
> >> + break;
> >> + }
> >> +
> >> + default:
> >> + /*
> >> + * Should not be reached unless arch_monitor_get_capabilities() is
> >> + * not properly implemented.
> >> + */
> >> + ASSERT_UNREACHABLE();
> >> + return -EOPNOTSUPP;
> >> + }
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +int monitor_smc(void)
> >> +{
> >> + struct vcpu *curr = current;
> >> + vm_event_request_t req = {
> >> + .reason = VM_EVENT_REASON_PRIVILEGED_CALL
> >> + };
> >> +
> >> + if ( !curr->domain->arch.monitor.privileged_call_enabled )
> >> + return 0;
> >
> > Isn't this check redundant? The only caller is do_trap_smc.
>
> No, it's necessary as Xen traps SMCs regardless if we have the monitor
> enabled or not. So we have to check if there is a listener to send
> this event to when we trap one. If there isn't, this just makes it so
> that we fall back to path that's the current default, injecting an
> undefined instruction exception.
Fair enough, but don't we have exactly the same check in do_trap_smc?
> >
> > Aside from that, it is OK for me.
> >
> >
> >> + return monitor_traps(curr, 1, &req);
> >> +}
> >> +
> >> +/*
> >> + * Local variables:
> >> + * mode: C
> >> + * c-file-style: "BSD"
> >> + * c-basic-offset: 4
> >> + * indent-tabs-mode: nil
> >> + * End:
> >> + */
> >> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> >> index 39a05fd..3555a28 100644
> >> --- a/xen/arch/arm/traps.c
> >> +++ b/xen/arch/arm/traps.c
> >> @@ -41,6 +41,7 @@
> >> #include <asm/mmio.h>
> >> #include <asm/cpufeature.h>
> >> #include <asm/flushtlb.h>
> >> +#include <asm/monitor.h>
> >>
> >> #include "decode.h"
> >> #include "vtimer.h"
> >> @@ -2527,6 +2528,17 @@ bad_data_abort:
> >> inject_dabt_exception(regs, info.gva, hsr.len);
> >> }
> >>
> >> +static void do_trap_smc(struct cpu_user_regs *regs, const union hsr hsr)
> >> +{
> >> + int rc = 0;
> >> +
> >> + if ( current->domain->arch.monitor.privileged_call_enabled )
> >> + rc = monitor_smc();
> >> +
> >> + if ( rc != 1 )
> >> + inject_undef_exception(regs, hsr);
> >> +}
> >> +
> >> static void enter_hypervisor_head(struct cpu_user_regs *regs)
> >> {
> >> if ( guest_mode(regs) )
> >> @@ -2602,7 +2614,7 @@ asmlinkage void do_trap_hypervisor(struct
> >> cpu_user_regs *regs)
> >> */
> >> GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
> >> perfc_incr(trap_smc32);
> >> - inject_undef32_exception(regs);
> >> + do_trap_smc(regs, hsr);
> >> break;
> >> case HSR_EC_HVC32:
> >> GUEST_BUG_ON(!psr_mode_is_32bit(regs->cpsr));
> >> @@ -2635,7 +2647,7 @@ asmlinkage void do_trap_hypervisor(struct
> >> cpu_user_regs *regs)
> >> */
> >> GUEST_BUG_ON(psr_mode_is_32bit(regs->cpsr));
> >> perfc_incr(trap_smc64);
> >> - inject_undef64_exception(regs, hsr.len);
> >> + do_trap_smc(regs, hsr);
> >> break;
> >> case HSR_EC_SYSREG:
> >> GUEST_BUG_ON(psr_mode_is_32bit(regs->cpsr));
> >> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> >> index 9452fcd..2d6fbb1 100644
> >> --- a/xen/include/asm-arm/domain.h
> >> +++ b/xen/include/asm-arm/domain.h
> >> @@ -126,6 +126,11 @@ struct arch_domain
> >> paddr_t efi_acpi_gpa;
> >> paddr_t efi_acpi_len;
> >> #endif
> >> +
> >> + /* Monitor options */
> >> + struct {
> >> + uint8_t privileged_call_enabled : 1;
> >> + } monitor;
> >> } __cacheline_aligned;
> >>
> >> struct arch_vcpu
> >> diff --git a/xen/include/asm-arm/monitor.h b/xen/include/asm-arm/monitor.h
> >> index 4af707a..1c4fea3 100644
> >> --- a/xen/include/asm-arm/monitor.h
> >> +++ b/xen/include/asm-arm/monitor.h
> >> @@ -32,19 +32,8 @@ int arch_monitor_domctl_op(struct domain *d, struct
> >> xen_domctl_monitor_op *mop)
> >> return -EOPNOTSUPP;
> >> }
> >>
> >> -static inline
> >> int arch_monitor_domctl_event(struct domain *d,
> >> - struct xen_domctl_monitor_op *mop)
> >> -{
> >> - /*
> >> - * No arch-specific monitor vm-events on ARM.
> >> - *
> >> - * Should not be reached unless arch_monitor_get_capabilities() is not
> >> - * properly implemented.
> >> - */
> >> - ASSERT_UNREACHABLE();
> >> - return -EOPNOTSUPP;
> >> -}
> >> + struct xen_domctl_monitor_op *mop);
> >>
> >> static inline
> >> int arch_monitor_init_domain(struct domain *d)
> >> @@ -63,9 +52,12 @@ static inline uint32_t
> >> arch_monitor_get_capabilities(struct domain *d)
> >> {
> >> uint32_t capabilities = 0;
> >>
> >> - capabilities = (1U << XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST);
> >> + capabilities = (1U << XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST |
> >> + 1U << XEN_DOMCTL_MONITOR_EVENT_PRIVILEGED_CALL);
> >>
> >> return capabilities;
> >> }
> >>
> >> +int monitor_smc(void);
> >> +
> >> #endif /* __ASM_ARM_MONITOR_H__ */
> >> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> >> index ddd3de4..177319d 100644
> >> --- a/xen/include/public/domctl.h
> >> +++ b/xen/include/public/domctl.h
> >> @@ -1085,6 +1085,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_domctl_psr_cmt_op_t);
> >> #define XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST 4
> >> #define XEN_DOMCTL_MONITOR_EVENT_DEBUG_EXCEPTION 5
> >> #define XEN_DOMCTL_MONITOR_EVENT_CPUID 6
> >> +#define XEN_DOMCTL_MONITOR_EVENT_PRIVILEGED_CALL 7
> >>
> >> struct xen_domctl_monitor_op {
> >> uint32_t op; /* XEN_DOMCTL_MONITOR_OP_* */
> >> diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
> >> index f756126..b251f68 100644
> >> --- a/xen/include/public/vm_event.h
> >> +++ b/xen/include/public/vm_event.h
> >> @@ -124,6 +124,13 @@
> >> #define VM_EVENT_REASON_DEBUG_EXCEPTION 9
> >> /* CPUID executed */
> >> #define VM_EVENT_REASON_CPUID 10
> >> +/*
> >> + * Privileged call executed (e.g. SMC).
> >> + * Note: event may be generated even if SMC condition check fails on some
> >> CPUs.
> >> + * As this behavior is CPU-specific, users are advised to not rely
> >> on it.
> >> + * These kinds of events will be filtered out in future versions.
> >> + */
> >> +#define VM_EVENT_REASON_PRIVILEGED_CALL 11
> >
> > It is acceptable
> >
> >> /* Supported values for the vm_event_write_ctrlreg index. */
> >> #define VM_EVENT_X86_CR0 0
>
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