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?
>
> 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?
> /* 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
