On Tue, Feb 16, 2016 at 6:07 PM, Alex Bennée <alex.ben...@linaro.org> wrote: > > Alvise Rigo <a.r...@virtualopensystems.com> writes: > >> Add a circular buffer to store the hw addresses used in the last >> EXCLUSIVE_HISTORY_LEN exclusive accesses. >> >> When an address is pop'ed from the buffer, its page will be set as not >> exclusive. In this way, we avoid: >> - frequent set/unset of a page (causing frequent flushes as well) >> - the possibility to forget the EXCL bit set. > > Why was this a possibility before? Shouldn't that be tackled in the > patch that introduced it?
Yes and no. The problem happens for instance when a LL will not be followed by the SC. In this situation, the flag will be set for the page, but might remain set for the rest of the execution (unless a complete LL/SC in performed later on in the same guest page). > >> >> Suggested-by: Jani Kokkonen <jani.kokko...@huawei.com> >> Suggested-by: Claudio Fontana <claudio.font...@huawei.com> >> Signed-off-by: Alvise Rigo <a.r...@virtualopensystems.com> >> --- >> cputlb.c | 29 +++++++++++++++++++---------- >> exec.c | 19 +++++++++++++++++++ >> include/qom/cpu.h | 8 ++++++++ >> softmmu_llsc_template.h | 1 + >> vl.c | 3 +++ >> 5 files changed, 50 insertions(+), 10 deletions(-) >> >> diff --git a/cputlb.c b/cputlb.c >> index 06ce2da..f3c4d97 100644 >> --- a/cputlb.c >> +++ b/cputlb.c >> @@ -395,16 +395,6 @@ void tlb_set_page_with_attrs(CPUState *cpu, >> target_ulong vaddr, >> env->tlb_v_table[mmu_idx][vidx] = *te; >> env->iotlb_v[mmu_idx][vidx] = env->iotlb[mmu_idx][index]; >> >> - if (unlikely(!(te->addr_write & TLB_MMIO) && (te->addr_write & >> TLB_EXCL))) { >> - /* We are removing an exclusive entry, set the page to dirty. This >> - * is not be necessary if the vCPU has performed both SC and LL. */ >> - hwaddr hw_addr = (env->iotlb[mmu_idx][index].addr & >> TARGET_PAGE_MASK) + >> - (te->addr_write & >> TARGET_PAGE_MASK); >> - if (!cpu->ll_sc_context) { >> - cpu_physical_memory_unset_excl(hw_addr); >> - } >> - } >> - > > Errm is this right? I got confused reviewing 8/16 because my final tree > didn't have this code. I'm not sure the adding of history obviates the > need to clear the exclusive flag? We will clear it adding a new item to the history. When an entry is added, the oldest is removed and cleaned, solving the problem mentioned above. Thank you, alvise > >> /* refill the tlb */ >> env->iotlb[mmu_idx][index].addr = iotlb - vaddr; >> env->iotlb[mmu_idx][index].attrs = attrs; >> @@ -517,6 +507,25 @@ static inline bool lookup_and_reset_cpus_ll_addr(hwaddr >> addr, hwaddr size) >> return ret; >> } >> >> +extern CPUExclusiveHistory excl_history; >> +static inline void excl_history_put_addr(hwaddr addr) >> +{ >> + hwaddr last; >> + >> + /* Calculate the index of the next exclusive address */ >> + excl_history.last_idx = (excl_history.last_idx + 1) % >> excl_history.length; >> + >> + last = excl_history.c_array[excl_history.last_idx]; >> + >> + /* Unset EXCL bit of the oldest entry */ >> + if (last != EXCLUSIVE_RESET_ADDR) { >> + cpu_physical_memory_unset_excl(last); >> + } >> + >> + /* Add a new address, overwriting the oldest one */ >> + excl_history.c_array[excl_history.last_idx] = addr & TARGET_PAGE_MASK; >> +} >> + >> #define MMUSUFFIX _mmu >> >> /* Generates LoadLink/StoreConditional helpers in softmmu_template.h */ >> diff --git a/exec.c b/exec.c >> index 51f366d..2e123f1 100644 >> --- a/exec.c >> +++ b/exec.c >> @@ -177,6 +177,25 @@ struct CPUAddressSpace { >> MemoryListener tcg_as_listener; >> }; >> >> +/* Exclusive memory support */ >> +CPUExclusiveHistory excl_history; >> +void cpu_exclusive_history_init(void) >> +{ >> + /* Initialize exclusive history for atomic instruction handling. */ >> + if (tcg_enabled()) { >> + g_assert(EXCLUSIVE_HISTORY_CPU_LEN * max_cpus <= UINT16_MAX); >> + excl_history.length = EXCLUSIVE_HISTORY_CPU_LEN * max_cpus; >> + excl_history.c_array = g_malloc(excl_history.length * >> sizeof(hwaddr)); >> + memset(excl_history.c_array, -1, excl_history.length * >> sizeof(hwaddr)); >> + } >> +} >> + >> +void cpu_exclusive_history_free(void) >> +{ >> + if (tcg_enabled()) { >> + g_free(excl_history.c_array); >> + } >> +} >> #endif >> >> #if !defined(CONFIG_USER_ONLY) >> diff --git a/include/qom/cpu.h b/include/qom/cpu.h >> index 6f6c1c0..0452fd0 100644 >> --- a/include/qom/cpu.h >> +++ b/include/qom/cpu.h >> @@ -227,7 +227,15 @@ struct kvm_run; >> #define TB_JMP_CACHE_SIZE (1 << TB_JMP_CACHE_BITS) >> >> /* Atomic insn translation TLB support. */ >> +typedef struct CPUExclusiveHistory { >> + uint16_t last_idx; /* index of last insertion */ >> + uint16_t length; /* history's length, it depends on >> smp_cpus */ >> + hwaddr *c_array; /* history's circular array */ >> +} CPUExclusiveHistory; >> #define EXCLUSIVE_RESET_ADDR ULLONG_MAX >> +#define EXCLUSIVE_HISTORY_CPU_LEN 256 >> +void cpu_exclusive_history_init(void); >> +void cpu_exclusive_history_free(void); >> >> /** >> * CPUState: >> diff --git a/softmmu_llsc_template.h b/softmmu_llsc_template.h >> index b4712ba..b4e7f9d 100644 >> --- a/softmmu_llsc_template.h >> +++ b/softmmu_llsc_template.h >> @@ -75,6 +75,7 @@ WORD_TYPE helper_ldlink_name(CPUArchState *env, >> target_ulong addr, >> * to request any flush. */ >> if (!cpu_physical_memory_is_excl(hw_addr)) { >> cpu_physical_memory_set_excl(hw_addr); >> + excl_history_put_addr(hw_addr); >> CPU_FOREACH(cpu) { >> if (current_cpu != cpu) { >> tlb_flush(cpu, 1); >> diff --git a/vl.c b/vl.c >> index f043009..b22d99b 100644 >> --- a/vl.c >> +++ b/vl.c >> @@ -547,6 +547,7 @@ static void res_free(void) >> { >> g_free(boot_splash_filedata); >> boot_splash_filedata = NULL; >> + cpu_exclusive_history_free(); >> } >> >> static int default_driver_check(void *opaque, QemuOpts *opts, Error **errp) >> @@ -4322,6 +4323,8 @@ int main(int argc, char **argv, char **envp) >> >> configure_accelerator(current_machine); >> >> + cpu_exclusive_history_init(); >> + >> if (qtest_chrdev) { >> qtest_init(qtest_chrdev, qtest_log, &error_fatal); >> } > > > -- > Alex Bennée