| Message ID | 20240223162202.1936541-22-alex.bennee@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | maintainer updates for 9.0 pre-PR (tests, plugin register support) | expand |
On 2024/02/24 1:21, Alex Bennée wrote: > We can only request a list of registers once the vCPU has been > initialised so the user needs to use either call the get function on > vCPU initialisation or during the translation phase. > > We don't expose the reg number to the plugin instead hiding it behind > an opaque handle. As the register set is potentially different for > each vCPU we store a separate set of handles for each vCPU. This will > become more important if we are able to emulate more heterogeneous > systems. > > Having an internal state within the plugins also allows us to expand > the interface in future (for example providing callbacks on register > change if the translator can track changes). > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1706 > Cc: Akihiko Odaki <akihiko.odaki@daynix.com> > Message-Id: <20240103173349.398526-39-alex.bennee@linaro.org> > Based-on: <20231025093128.33116-18-akihiko.odaki@daynix.com> > Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org> > > --- > v4 > - the get/read_registers functions are now implicitly for current > vCPU only to accidental cpu != current_cpu uses. > v5 > - make reg_handles as per-CPUPluginState variable. > --- > include/qemu/plugin.h | 2 + > include/qemu/qemu-plugin.h | 48 +++++++++++++++++++- > plugins/api.c | 88 ++++++++++++++++++++++++++++++++++++ > plugins/qemu-plugins.symbols | 2 + > 4 files changed, 138 insertions(+), 2 deletions(-) > > diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h > index 0e7b9693d80..64fb425fb0b 100644 > --- a/include/qemu/plugin.h > +++ b/include/qemu/plugin.h > @@ -189,9 +189,11 @@ struct qemu_plugin_insn *qemu_plugin_tb_insn_get(struct qemu_plugin_tb *tb, > /** > * struct CPUPluginState - per-CPU state for plugins > * @event_mask: plugin event bitmap. Modified only via async work. > + * @reg_handles: hash table of register handles. > */ > struct CPUPluginState { > DECLARE_BITMAP(event_mask, QEMU_PLUGIN_EV_MAX); > + GHashTable *reg_handles; > }; > > /** > diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h > index 93981f8f89f..3b6b18058d2 100644 > --- a/include/qemu/qemu-plugin.h > +++ b/include/qemu/qemu-plugin.h > @@ -11,6 +11,7 @@ > #ifndef QEMU_QEMU_PLUGIN_H > #define QEMU_QEMU_PLUGIN_H > > +#include <glib.h> > #include <inttypes.h> > #include <stdbool.h> > #include <stddef.h> > @@ -229,8 +230,8 @@ struct qemu_plugin_insn; > * @QEMU_PLUGIN_CB_R_REGS: callback reads the CPU's regs > * @QEMU_PLUGIN_CB_RW_REGS: callback reads and writes the CPU's regs > * > - * Note: currently unused, plugins cannot read or change system > - * register state. > + * Note: currently QEMU_PLUGIN_CB_RW_REGS is unused, plugins cannot change > + * system register state. > */ > enum qemu_plugin_cb_flags { > QEMU_PLUGIN_CB_NO_REGS, > @@ -707,4 +708,47 @@ uint64_t qemu_plugin_end_code(void); > QEMU_PLUGIN_API > uint64_t qemu_plugin_entry_code(void); > > +/** struct qemu_plugin_register - Opaque handle for register access */ > +struct qemu_plugin_register; > + > +/** > + * typedef qemu_plugin_reg_descriptor - register descriptions > + * > + * @handle: opaque handle for retrieving value with qemu_plugin_read_register > + * @name: register name > + * @feature: optional feature descriptor, can be NULL > + */ > +typedef struct { > + struct qemu_plugin_register *handle; > + const char *name; > + const char *feature; > +} qemu_plugin_reg_descriptor; > + > +/** > + * qemu_plugin_get_registers() - return register list for current vCPU > + * > + * Returns a GArray of qemu_plugin_reg_descriptor or NULL. Caller > + * frees the array (but not the const strings). > + * > + * Should be used from a qemu_plugin_register_vcpu_init_cb() callback > + * after the vCPU is initialised, i.e. in the vCPU context. > + */ > +GArray *qemu_plugin_get_registers(void); > + > +/** > + * qemu_plugin_read_register() - read register for current vCPU > + * > + * @handle: a @qemu_plugin_reg_handle handle > + * @buf: A GByteArray for the data owned by the plugin > + * > + * This function is only available in a context that register read access is > + * explicitly requested via the QEMU_PLUGIN_CB_R_REGS flag. > + * > + * Returns the size of the read register. The content of @buf is in target byte > + * order. On failure returns -1 > + */ > +int qemu_plugin_read_register(struct qemu_plugin_register *handle, > + GByteArray *buf); > + > + > #endif /* QEMU_QEMU_PLUGIN_H */ > diff --git a/plugins/api.c b/plugins/api.c > index 54df72c1c00..f6c3ba2366f 100644 > --- a/plugins/api.c > +++ b/plugins/api.c > @@ -8,6 +8,7 @@ > * > * qemu_plugin_tb > * qemu_plugin_insn > + * qemu_plugin_register > * > * Which can then be passed back into the API to do additional things. > * As such all the public functions in here are exported in > @@ -35,10 +36,12 @@ > */ > > #include "qemu/osdep.h" > +#include "qemu/main-loop.h" > #include "qemu/plugin.h" > #include "qemu/log.h" > #include "tcg/tcg.h" > #include "exec/exec-all.h" > +#include "exec/gdbstub.h" > #include "exec/ram_addr.h" > #include "disas/disas.h" > #include "plugin.h" > @@ -410,3 +413,88 @@ uint64_t qemu_plugin_entry_code(void) > #endif > return entry; > } > + > +/* > + * Register handles > + * > + * The plugin infrastructure keeps hold of these internal data > + * structures which are presented to plugins as opaque handles. They > + * are local to each vCPU as there can be slight variations for each > + * vCPU depending on enabled features. We track this in > + * CPUPluginState. > + */ Since we do no longer coalesce registers for different classes, I need to bring my old question back: Why don't you just cast register numbers into pointers and use it as handles? You can even just expose gdb_reg_num with the interface. > + > +struct qemu_plugin_register { > + const char *name; > + int gdb_reg_num; > +}; > + > +/* > + * Create register handles. > + * > + * We need to create a handle for each register so the plugin > + * infrastructure can call gdbstub to read a register. We also > + * construct a result array with those handles and some ancillary data > + * the plugin might find useful. > + */ > + > +static GArray *create_register_handles(CPUState *cs, GArray *gdbstub_regs) > +{ > + GArray *find_data = g_array_new(true, true, > + sizeof(qemu_plugin_reg_descriptor)); > + > + if (!cs->plugin_state->reg_handles) { > + cs->plugin_state->reg_handles = g_hash_table_new(g_direct_hash, > + g_direct_equal); > + } > + > + for (int i = 0; i < gdbstub_regs->len; i++) { > + GDBRegDesc *grd = &g_array_index(gdbstub_regs, GDBRegDesc, i); > + gpointer key = GINT_TO_POINTER(grd->gdb_reg); > + struct qemu_plugin_register *val > + = g_hash_table_lookup(cs->plugin_state->reg_handles, > + key); > + > + /* skip "un-named" regs */ > + if (!grd->name) { > + continue; > + } > + > + /* Doesn't exist, create one */ > + if (!val) { > + val = g_new0(struct qemu_plugin_register, 1); > + val->gdb_reg_num = grd->gdb_reg; > + val->name = g_intern_string(grd->name); > + > + g_hash_table_insert(cs->plugin_state->reg_handles, key, val); > + } else { > + /* make sure we are not seeing a key clash */ > + g_assert(val->gdb_reg_num == grd->gdb_reg); > + } > + > + /* Create a record for the plugin */ > + qemu_plugin_reg_descriptor desc = { > + .handle = val, > + .name = val->name, > + .feature = g_intern_string(grd->feature_name) > + }; > + g_array_append_val(find_data, desc); > + } > + > + return find_data; > +} > + > +GArray *qemu_plugin_get_registers(void) > +{ > + g_assert(current_cpu); > + > + g_autoptr(GArray) regs = gdb_get_register_list(current_cpu); > + return regs->len ? create_register_handles(current_cpu, regs) : NULL; > +} > + > +int qemu_plugin_read_register(struct qemu_plugin_register *reg, GByteArray *buf) > +{ > + g_assert(current_cpu); > + > + return gdb_read_register(current_cpu, buf, reg->gdb_reg_num); > +} > diff --git a/plugins/qemu-plugins.symbols b/plugins/qemu-plugins.symbols > index adb67608598..27fe97239be 100644 > --- a/plugins/qemu-plugins.symbols > +++ b/plugins/qemu-plugins.symbols > @@ -3,6 +3,7 @@ > qemu_plugin_end_code; > qemu_plugin_entry_code; > qemu_plugin_get_hwaddr; > + qemu_plugin_get_registers; > qemu_plugin_hwaddr_device_name; > qemu_plugin_hwaddr_is_io; > qemu_plugin_hwaddr_phys_addr; > @@ -19,6 +20,7 @@ > qemu_plugin_num_vcpus; > qemu_plugin_outs; > qemu_plugin_path_to_binary; > + qemu_plugin_read_register; > qemu_plugin_register_atexit_cb; > qemu_plugin_register_flush_cb; > qemu_plugin_register_vcpu_exit_cb;
Akihiko Odaki <akihiko.odaki@daynix.com> writes: > On 2024/02/24 1:21, Alex Bennée wrote: >> We can only request a list of registers once the vCPU has been >> initialised so the user needs to use either call the get function on >> vCPU initialisation or during the translation phase. >> We don't expose the reg number to the plugin instead hiding it >> behind >> an opaque handle. As the register set is potentially different for >> each vCPU we store a separate set of handles for each vCPU. This will >> become more important if we are able to emulate more heterogeneous >> systems. >> Having an internal state within the plugins also allows us to expand >> the interface in future (for example providing callbacks on register >> change if the translator can track changes). <snip> >> + >> +/* >> + * Register handles >> + * >> + * The plugin infrastructure keeps hold of these internal data >> + * structures which are presented to plugins as opaque handles. They >> + * are local to each vCPU as there can be slight variations for each >> + * vCPU depending on enabled features. We track this in >> + * CPUPluginState. >> + */ > > Since we do no longer coalesce registers for different classes, I need > to bring my old question back: Why don't you just cast register > numbers into pointers and use it as handles? In the interest of getting this merged before the fast approaching soft-freeze I shall do this for now. However once the plugin system has knowledge of individual registers exposed by TCG it will need to track internal state so will need some sort of container for that. > You can even just expose gdb_reg_num with the interface. As I have explained before I don't want plugins to treat the handle as a pure index in case they start providing numbers that aren't in the list provided by qemu_plugin_get_registers.
On 2024/02/26 20:12, Alex Bennée wrote: > Akihiko Odaki <akihiko.odaki@daynix.com> writes: > >> On 2024/02/24 1:21, Alex Bennée wrote: >>> We can only request a list of registers once the vCPU has been >>> initialised so the user needs to use either call the get function on >>> vCPU initialisation or during the translation phase. >>> We don't expose the reg number to the plugin instead hiding it >>> behind >>> an opaque handle. As the register set is potentially different for >>> each vCPU we store a separate set of handles for each vCPU. This will >>> become more important if we are able to emulate more heterogeneous >>> systems. >>> Having an internal state within the plugins also allows us to expand >>> the interface in future (for example providing callbacks on register >>> change if the translator can track changes). > <snip> >>> + >>> +/* >>> + * Register handles >>> + * >>> + * The plugin infrastructure keeps hold of these internal data >>> + * structures which are presented to plugins as opaque handles. They >>> + * are local to each vCPU as there can be slight variations for each >>> + * vCPU depending on enabled features. We track this in >>> + * CPUPluginState. >>> + */ >> >> Since we do no longer coalesce registers for different classes, I need >> to bring my old question back: Why don't you just cast register >> numbers into pointers and use it as handles? > > In the interest of getting this merged before the fast approaching > soft-freeze I shall do this for now. However once the plugin system has > knowledge of individual registers exposed by TCG it will need to track > internal state so will need some sort of container for that. Indeed it's likely that we would have containers for registers, but we don't know who would own them yet. These containers may not be held by vCPU classes as you previously proposed because we may support different configurations of one vCPU class. The current proposal to allocate handles for each vCPU may not be what we would want to do in the future either. To support SMP debugging with gdbstub, gdbstub must know sets of vCPUs that have identical registers, and once it does, it's better to allocate handles for each of such sets, not each of vCPUs. Let's figure out how we should manage containers when a need arises. > >> You can even just expose gdb_reg_num with the interface. > > As I have explained before I don't want plugins to treat the handle as > a pure index in case they start providing numbers that aren't in the > list provided by qemu_plugin_get_registers. > You can assert the given number has an associated name.
diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h index 0e7b9693d80..64fb425fb0b 100644 --- a/include/qemu/plugin.h +++ b/include/qemu/plugin.h @@ -189,9 +189,11 @@ struct qemu_plugin_insn *qemu_plugin_tb_insn_get(struct qemu_plugin_tb *tb, /** * struct CPUPluginState - per-CPU state for plugins * @event_mask: plugin event bitmap. Modified only via async work. + * @reg_handles: hash table of register handles. */ struct CPUPluginState { DECLARE_BITMAP(event_mask, QEMU_PLUGIN_EV_MAX); + GHashTable *reg_handles; }; /** diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h index 93981f8f89f..3b6b18058d2 100644 --- a/include/qemu/qemu-plugin.h +++ b/include/qemu/qemu-plugin.h @@ -11,6 +11,7 @@ #ifndef QEMU_QEMU_PLUGIN_H #define QEMU_QEMU_PLUGIN_H +#include <glib.h> #include <inttypes.h> #include <stdbool.h> #include <stddef.h> @@ -229,8 +230,8 @@ struct qemu_plugin_insn; * @QEMU_PLUGIN_CB_R_REGS: callback reads the CPU's regs * @QEMU_PLUGIN_CB_RW_REGS: callback reads and writes the CPU's regs * - * Note: currently unused, plugins cannot read or change system - * register state. + * Note: currently QEMU_PLUGIN_CB_RW_REGS is unused, plugins cannot change + * system register state. */ enum qemu_plugin_cb_flags { QEMU_PLUGIN_CB_NO_REGS, @@ -707,4 +708,47 @@ uint64_t qemu_plugin_end_code(void); QEMU_PLUGIN_API uint64_t qemu_plugin_entry_code(void); +/** struct qemu_plugin_register - Opaque handle for register access */ +struct qemu_plugin_register; + +/** + * typedef qemu_plugin_reg_descriptor - register descriptions + * + * @handle: opaque handle for retrieving value with qemu_plugin_read_register + * @name: register name + * @feature: optional feature descriptor, can be NULL + */ +typedef struct { + struct qemu_plugin_register *handle; + const char *name; + const char *feature; +} qemu_plugin_reg_descriptor; + +/** + * qemu_plugin_get_registers() - return register list for current vCPU + * + * Returns a GArray of qemu_plugin_reg_descriptor or NULL. Caller + * frees the array (but not the const strings). + * + * Should be used from a qemu_plugin_register_vcpu_init_cb() callback + * after the vCPU is initialised, i.e. in the vCPU context. + */ +GArray *qemu_plugin_get_registers(void); + +/** + * qemu_plugin_read_register() - read register for current vCPU + * + * @handle: a @qemu_plugin_reg_handle handle + * @buf: A GByteArray for the data owned by the plugin + * + * This function is only available in a context that register read access is + * explicitly requested via the QEMU_PLUGIN_CB_R_REGS flag. + * + * Returns the size of the read register. The content of @buf is in target byte + * order. On failure returns -1 + */ +int qemu_plugin_read_register(struct qemu_plugin_register *handle, + GByteArray *buf); + + #endif /* QEMU_QEMU_PLUGIN_H */ diff --git a/plugins/api.c b/plugins/api.c index 54df72c1c00..f6c3ba2366f 100644 --- a/plugins/api.c +++ b/plugins/api.c @@ -8,6 +8,7 @@ * * qemu_plugin_tb * qemu_plugin_insn + * qemu_plugin_register * * Which can then be passed back into the API to do additional things. * As such all the public functions in here are exported in @@ -35,10 +36,12 @@ */ #include "qemu/osdep.h" +#include "qemu/main-loop.h" #include "qemu/plugin.h" #include "qemu/log.h" #include "tcg/tcg.h" #include "exec/exec-all.h" +#include "exec/gdbstub.h" #include "exec/ram_addr.h" #include "disas/disas.h" #include "plugin.h" @@ -410,3 +413,88 @@ uint64_t qemu_plugin_entry_code(void) #endif return entry; } + +/* + * Register handles + * + * The plugin infrastructure keeps hold of these internal data + * structures which are presented to plugins as opaque handles. They + * are local to each vCPU as there can be slight variations for each + * vCPU depending on enabled features. We track this in + * CPUPluginState. + */ + +struct qemu_plugin_register { + const char *name; + int gdb_reg_num; +}; + +/* + * Create register handles. + * + * We need to create a handle for each register so the plugin + * infrastructure can call gdbstub to read a register. We also + * construct a result array with those handles and some ancillary data + * the plugin might find useful. + */ + +static GArray *create_register_handles(CPUState *cs, GArray *gdbstub_regs) +{ + GArray *find_data = g_array_new(true, true, + sizeof(qemu_plugin_reg_descriptor)); + + if (!cs->plugin_state->reg_handles) { + cs->plugin_state->reg_handles = g_hash_table_new(g_direct_hash, + g_direct_equal); + } + + for (int i = 0; i < gdbstub_regs->len; i++) { + GDBRegDesc *grd = &g_array_index(gdbstub_regs, GDBRegDesc, i); + gpointer key = GINT_TO_POINTER(grd->gdb_reg); + struct qemu_plugin_register *val + = g_hash_table_lookup(cs->plugin_state->reg_handles, + key); + + /* skip "un-named" regs */ + if (!grd->name) { + continue; + } + + /* Doesn't exist, create one */ + if (!val) { + val = g_new0(struct qemu_plugin_register, 1); + val->gdb_reg_num = grd->gdb_reg; + val->name = g_intern_string(grd->name); + + g_hash_table_insert(cs->plugin_state->reg_handles, key, val); + } else { + /* make sure we are not seeing a key clash */ + g_assert(val->gdb_reg_num == grd->gdb_reg); + } + + /* Create a record for the plugin */ + qemu_plugin_reg_descriptor desc = { + .handle = val, + .name = val->name, + .feature = g_intern_string(grd->feature_name) + }; + g_array_append_val(find_data, desc); + } + + return find_data; +} + +GArray *qemu_plugin_get_registers(void) +{ + g_assert(current_cpu); + + g_autoptr(GArray) regs = gdb_get_register_list(current_cpu); + return regs->len ? create_register_handles(current_cpu, regs) : NULL; +} + +int qemu_plugin_read_register(struct qemu_plugin_register *reg, GByteArray *buf) +{ + g_assert(current_cpu); + + return gdb_read_register(current_cpu, buf, reg->gdb_reg_num); +} diff --git a/plugins/qemu-plugins.symbols b/plugins/qemu-plugins.symbols index adb67608598..27fe97239be 100644 --- a/plugins/qemu-plugins.symbols +++ b/plugins/qemu-plugins.symbols @@ -3,6 +3,7 @@ qemu_plugin_end_code; qemu_plugin_entry_code; qemu_plugin_get_hwaddr; + qemu_plugin_get_registers; qemu_plugin_hwaddr_device_name; qemu_plugin_hwaddr_is_io; qemu_plugin_hwaddr_phys_addr; @@ -19,6 +20,7 @@ qemu_plugin_num_vcpus; qemu_plugin_outs; qemu_plugin_path_to_binary; + qemu_plugin_read_register; qemu_plugin_register_atexit_cb; qemu_plugin_register_flush_cb; qemu_plugin_register_vcpu_exit_cb;