On Mon, 2021-04-19 at 17:29 +0100, Alex Bennée wrote:
> Maxim Levitsky <mlevitsk@xxxxxxxxxx> writes:
>
> > Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> > ---
> > accel/kvm/kvm-all.c | 25 +++++++++++++++++++
> > gdbstub.c | 59 ++++++++++++++++++++++++++++++++++++--------
> > include/sysemu/kvm.h | 13 ++++++++++
> > 3 files changed, 87 insertions(+), 10 deletions(-)
> >
> > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> > index b6d9f92f15..bc7955fb19 100644
> > --- a/accel/kvm/kvm-all.c
> > +++ b/accel/kvm/kvm-all.c
> > @@ -147,6 +147,8 @@ bool kvm_vm_attributes_allowed;
> > bool kvm_direct_msi_allowed;
> > bool kvm_ioeventfd_any_length_allowed;
> > bool kvm_msi_use_devid;
> > +bool kvm_has_guest_debug;
> > +int kvm_sstep_flags;
> > static bool kvm_immediate_exit;
> > static hwaddr kvm_max_slot_size = ~0;
> >
> > @@ -2186,6 +2188,25 @@ static int kvm_init(MachineState *ms)
> > kvm_ioeventfd_any_length_allowed =
> > (kvm_check_extension(s, KVM_CAP_IOEVENTFD_ANY_LENGTH) > 0);
> >
> > + kvm_has_guest_debug =
> > + (kvm_check_extension(s, KVM_CAP_SET_GUEST_DEBUG) > 0);
> > +
> > + kvm_sstep_flags = 0;
> > +
> > + if (kvm_has_guest_debug) {
> > + /* Assume that single stepping is supported */
> > + kvm_sstep_flags = SSTEP_ENABLE;
> > +
> > + int guest_debug_flags =
> > + kvm_check_extension(s, KVM_CAP_SET_GUEST_DEBUG2);
> > +
> > + if (guest_debug_flags > 0) {
> > + if (guest_debug_flags & KVM_GUESTDBG_BLOCKIRQ) {
> > + kvm_sstep_flags |= SSTEP_NOIRQ;
> > + }
> > + }
> > + }
> > +
> > kvm_state = s;
> >
> > ret = kvm_arch_init(ms, s);
> > @@ -2796,6 +2817,10 @@ int kvm_update_guest_debug(CPUState *cpu, unsigned long reinject_trap)
> >
> > if (cpu->singlestep_enabled) {
> > data.dbg.control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP;
> > +
> > + if (cpu->singlestep_enabled & SSTEP_NOIRQ) {
> > + data.dbg.control |= KVM_GUESTDBG_BLOCKIRQ;
> > + }
> > }
> > kvm_arch_update_guest_debug(cpu, &data.dbg);
> >
> > diff --git a/gdbstub.c b/gdbstub.c
> > index 054665e93e..f789ded99d 100644
> > --- a/gdbstub.c
> > +++ b/gdbstub.c
> > @@ -369,12 +369,11 @@ typedef struct GDBState {
> > gdb_syscall_complete_cb current_syscall_cb;
> > GString *str_buf;
> > GByteArray *mem_buf;
> > + int sstep_flags;
> > + int supported_sstep_flags;
> > } GDBState;
> >
> > -/* By default use no IRQs and no timers while single stepping so as to
> > - * make single stepping like an ICE HW step.
> > - */
> > -static int sstep_flags = SSTEP_ENABLE|SSTEP_NOIRQ|SSTEP_NOTIMER;
> > +static GDBState gdbserver_state;
> >
> > /* Retrieves flags for single step mode. */
> > static int get_sstep_flags(void)
> > @@ -386,11 +385,10 @@ static int get_sstep_flags(void)
> > if (replay_mode != REPLAY_MODE_NONE) {
> > return SSTEP_ENABLE;
> > } else {
> > - return sstep_flags;
> > + return gdbserver_state.sstep_flags;
> > }
> > }
> >
> > -static GDBState gdbserver_state;
> >
> > static void init_gdbserver_state(void)
> > {
> > @@ -400,6 +398,23 @@ static void init_gdbserver_state(void)
> > gdbserver_state.str_buf = g_string_new(NULL);
> > gdbserver_state.mem_buf = g_byte_array_sized_new(MAX_PACKET_LENGTH);
> > gdbserver_state.last_packet = g_byte_array_sized_new(MAX_PACKET_LENGTH + 4);
> > +
> > +
> > + if (kvm_enabled()) {
> > + gdbserver_state.supported_sstep_flags =
> > kvm_get_supported_sstep_flags();
>
> This falls over as soon as you build something without KVM support (like
> a TCG only build or an emulation only target):
This is something I'll check from now on before sending patches.
>
> [10/1152] Compiling C object libqemu-riscv32-softmmu.fa.p/gdbstub.c.o
> FAILED: libqemu-riscv32-softmmu.fa.p/gdbstub.c.o
> cc -Ilibqemu-riscv32-softmmu.fa.p -I. -I../.. -Itarget/riscv -I../../target/riscv -Idtc/libfdt -I../../dtc/libfdt -I../../capstone/include/capstone -Iqapi -Itrace -Iui -Iui/shader -I/usr/include/pixman-1 -I/usr/include/libdrm -I/usr/include/spice-server -I/usr/include/spice-1 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -fdiagnostics-color=auto -pipe -Wall -Winvalid-pch -Werror -std=gnu99 -O2 -g -isystem /home/alex/lsrc/qemu.git/linux-headers -isystem linux-headers -iquote . -iquote /home/alex/lsrc/qemu.git -iquote /home/alex/lsrc/qemu.git/include -iquote /home/alex/lsrc/qemu.git/disas/libvixl -iquote /home/alex/lsrc/qemu.git/tcg/i386 -iquote /home/alex/lsrc/qemu.git/accel/tcg -pthread -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -m64 -mcx16 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -Wstrict-prototypes -Wredundant-decls -Wundef -Wwrite-strings -Wmissing-prototypes -fno-strict-aliasing -fno-common -fwrapv -Wold-style-declaration -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined -Wimplicit-fallthrough=2 -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi -fstack-protector-strong -DLEGACY_RDMA_REG_MR -fPIC -isystem../../linux-headers -isystemlinux-headers -DNEED_CPU_H '-DCONFIG_TARGET="riscv32-softmmu-config-target.h"' '-DCONFIG_DEVICES="riscv32-softmmu-config-devices.h"' -MD -MQ libqemu-riscv32-softmmu.fa.p/gdbstub.c.o -MF libqemu-riscv32-softmmu.fa.p/gdbstub.c.o.d -o libqemu-riscv32-softmmu.fa.p/gdbstub.c.o -c ../../gdbstub.c
> ../../gdbstub.c: In function ‘init_gdbserver_state’:
> ../../gdbstub.c:404:49: error: implicit declaration of function ‘kvm_get_supported_sstep_flags’; did you mean ‘hvf_get_supported_cpuid’? [-Werror=implicit-function-declaration]
> gdbserver_state.supported_sstep_flags = kvm_get_supported_sstep_flags();
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> hvf_get_supported_cpuid
> ../../gdbstub.c:404:49: error: nested extern declaration of ‘kvm_get_supported_sstep_flags’ [-Werror=nested-externs]
> ../../gdbstub.c: In function ‘gdbserver_start’:
> ../../gdbstub.c:3536:27: error: implicit declaration of function ‘kvm_supports_guest_debug’; did you mean ‘kvm_update_guest_debug’? [-Werror=implicit-function-declaration]
> if (kvm_enabled() && !kvm_supports_guest_debug()) {
> ^~~~~~~~~~~~~~~~~~~~~~~~
> kvm_update_guest_debug
> ../../gdbstub.c:3536:27: error: nested extern declaration of ‘kvm_supports_guest_debug’ [-Werror=nested-externs]
> cc1: all warnings being treated as errors
>
>
> > + } else {
> > + gdbserver_state.supported_sstep_flags =
> > + SSTEP_ENABLE | SSTEP_NOIRQ | SSTEP_NOTIMER;
> > + }
> > +
> > + /*
> > + * By default use no IRQs and no timers while single stepping so as to
> > + * make single stepping like an ICE HW step.
> > + */
> > +
> > + gdbserver_state.sstep_flags = SSTEP_ENABLE | SSTEP_NOIRQ | SSTEP_NOTIMER;
> > + gdbserver_state.sstep_flags &= gdbserver_state.supported_sstep_flags;
> > +
> > }
> >
> > #ifndef CONFIG_USER_ONLY
> > @@ -2023,24 +2038,43 @@ static void handle_v_commands(GdbCmdContext *gdb_ctx, void *user_ctx)
> >
> > static void handle_query_qemu_sstepbits(GdbCmdContext *gdb_ctx, void *user_ctx)
> > {
> > - g_string_printf(gdbserver_state.str_buf, "ENABLE=%x,NOIRQ=%x,NOTIMER=%x",
> > - SSTEP_ENABLE, SSTEP_NOIRQ, SSTEP_NOTIMER);
> > + g_string_printf(gdbserver_state.str_buf, "ENABLE=%x", SSTEP_ENABLE);
> > +
> > + if (gdbserver_state.supported_sstep_flags & SSTEP_NOIRQ) {
> > + g_string_append_printf(gdbserver_state.str_buf, ",NOIRQ=%x",
> > + SSTEP_NOIRQ);
> > + }
> > +
> > + if (gdbserver_state.supported_sstep_flags & SSTEP_NOTIMER) {
> > + g_string_append_printf(gdbserver_state.str_buf, ",NOTIMER=%x",
> > + SSTEP_NOTIMER);
> > + }
> > +
> > put_strbuf();
> > }
> >
> > static void handle_set_qemu_sstep(GdbCmdContext *gdb_ctx, void *user_ctx)
> > {
> > + int new_sstep_flags;
> > if (!gdb_ctx->num_params) {
> > return;
> > }
> >
> > - sstep_flags = gdb_ctx->params[0].val_ul;
> > + new_sstep_flags = gdb_ctx->params[0].val_ul;
> > +
> > + if (new_sstep_flags & ~gdbserver_state.supported_sstep_flags) {
> > + put_packet("E22");
> > + return;
> > + }
> > +
> > + gdbserver_state.sstep_flags = new_sstep_flags;
> > put_packet("OK");
> > }
> >
> > static void handle_query_qemu_sstep(GdbCmdContext *gdb_ctx, void *user_ctx)
> > {
> > - g_string_printf(gdbserver_state.str_buf, "0x%x", sstep_flags);
> > + g_string_printf(gdbserver_state.str_buf, "0x%x",
> > + gdbserver_state.sstep_flags);
> > put_strbuf();
> > }
> >
> > @@ -3499,6 +3533,11 @@ int gdbserver_start(const char *device)
> > return -1;
> > }
> >
> > + if (kvm_enabled() && !kvm_supports_guest_debug()) {
> > + error_report("gdbstub: KVM doesn't support guest debugging");
> > + return -1;
> > + }
> > +
> <snip>
>
> Otherwise it looks fine as far as it goes, however it would be nice to
> have some sort of test in for this. The gdbstub has a hand-rolled gdb
> script in tests/guest-debug/test-gdbstub.py but it's not integrated with
> the rest of the testing.
I'll take a look!
>
> As I suspect you need a) KVM enabled, b) a recent enough kernel and c)
> some sort of guest kernel that is going to enable timers and IRQs this
> might be something worth porting to the acceptance tests.
>
> We have an example in tests/acceptance/reverse_debugging.py which is run
> as part of check-acceptance. It's TCG only but perhaps is a template for
> how such a test could be implemented.
Thanks for the review,
Best regards,
Maxim Levitsky
>
