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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 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.
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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