On Fri, Jul 07, 2023 at 11:36:11AM +0100, Richard Henderson wrote:
> We had done this for user-mode by invoking page_protect
> within the translator loop. Extend this to handle system
> mode as well. Move page locking out of tb_link_page.
>
> Reported-by: Liren Wei <lr...@bupt.edu.cn>
> Reported-by: Richard W.M. Jones <rjo...@redhat.com>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> Tested-by: Richard W.M. Jones <rjo...@redhat.com>
I tested another 5,000 iterations successfully, so this one looks good
as well. I don't have an easy way to test qemu-user, so I only tested
qemu-system-x86_64.
Rich.
> ---
> accel/tcg/internal.h | 30 ++++-
> accel/tcg/cpu-exec.c | 20 ++++
> accel/tcg/tb-maint.c | 242 ++++++++++++++++++++------------------
> accel/tcg/translate-all.c | 43 ++++++-
> accel/tcg/translator.c | 34 ++++--
> 5 files changed, 236 insertions(+), 133 deletions(-)
>
> diff --git a/accel/tcg/internal.h b/accel/tcg/internal.h
> index 650c3ac53f..e8cbbde581 100644
> --- a/accel/tcg/internal.h
> +++ b/accel/tcg/internal.h
> @@ -10,6 +10,7 @@
> #define ACCEL_TCG_INTERNAL_H
>
> #include "exec/exec-all.h"
> +#include "exec/translate-all.h"
>
> /*
> * Access to the various translations structures need to be serialised
> @@ -35,6 +36,32 @@ static inline void page_table_config_init(void) { }
> void page_table_config_init(void);
> #endif
>
> +#ifdef CONFIG_USER_ONLY
> +/*
> + * For user-only, page_protect sets the page read-only.
> + * Since most execution is already on read-only pages, and we'd need to
> + * account for other TBs on the same page, defer undoing any page protection
> + * until we receive the write fault.
> + */
> +static inline void tb_lock_page0(tb_page_addr_t p0)
> +{
> + page_protect(p0);
> +}
> +
> +static inline void tb_lock_page1(tb_page_addr_t p0, tb_page_addr_t p1)
> +{
> + page_protect(p1);
> +}
> +
> +static inline void tb_unlock_page1(tb_page_addr_t p0, tb_page_addr_t p1) { }
> +static inline void tb_unlock_pages(TranslationBlock *tb) { }
> +#else
> +void tb_lock_page0(tb_page_addr_t);
> +void tb_lock_page1(tb_page_addr_t, tb_page_addr_t);
> +void tb_unlock_page1(tb_page_addr_t, tb_page_addr_t);
> +void tb_unlock_pages(TranslationBlock *);
> +#endif
> +
> #ifdef CONFIG_SOFTMMU
> void tb_invalidate_phys_range_fast(ram_addr_t ram_addr,
> unsigned size,
> @@ -48,8 +75,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu, vaddr pc,
> void page_init(void);
> void tb_htable_init(void);
> void tb_reset_jump(TranslationBlock *tb, int n);
> -TranslationBlock *tb_link_page(TranslationBlock *tb, tb_page_addr_t phys_pc,
> - tb_page_addr_t phys_page2);
> +TranslationBlock *tb_link_page(TranslationBlock *tb);
> bool tb_invalidate_phys_page_unwind(tb_page_addr_t addr, uintptr_t pc);
> void cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
> uintptr_t host_pc);
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 31aa320513..fdd6d3e0e4 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -536,6 +536,26 @@ static void cpu_exec_longjmp_cleanup(CPUState *cpu)
> if (have_mmap_lock()) {
> mmap_unlock();
> }
> +#else
> + /*
> + * For softmmu, a tlb_fill fault during translation will land here,
> + * and we need to release any page locks held. In system mode we
> + * have one tcg_ctx per thread, so we know it was this cpu doing
> + * the translation.
> + *
> + * Alternative 1: Install a cleanup to be called via an exception
> + * handling safe longjmp. It seems plausible that all our hosts
> + * support such a thing. We'd have to properly register unwind info
> + * for the JIT for EH, rather that just for GDB.
> + *
> + * Alternative 2: Set and restore cpu->jmp_env in tb_gen_code to
> + * capture the cpu_loop_exit longjmp, perform the cleanup, and
> + * jump again to arrive here.
> + */
> + if (tcg_ctx->gen_tb) {
> + tb_unlock_pages(tcg_ctx->gen_tb);
> + tcg_ctx->gen_tb = NULL;
> + }
> #endif
> if (qemu_mutex_iothread_locked()) {
> qemu_mutex_unlock_iothread();
> diff --git a/accel/tcg/tb-maint.c b/accel/tcg/tb-maint.c
> index 9566224d18..c406b2f7b7 100644
> --- a/accel/tcg/tb-maint.c
> +++ b/accel/tcg/tb-maint.c
> @@ -70,17 +70,7 @@ typedef struct PageDesc PageDesc;
> */
> #define assert_page_locked(pd) tcg_debug_assert(have_mmap_lock())
>
> -static inline void page_lock_pair(PageDesc **ret_p1, tb_page_addr_t phys1,
> - PageDesc **ret_p2, tb_page_addr_t phys2,
> - bool alloc)
> -{
> - *ret_p1 = NULL;
> - *ret_p2 = NULL;
> -}
> -
> -static inline void page_unlock(PageDesc *pd) { }
> -static inline void page_lock_tb(const TranslationBlock *tb) { }
> -static inline void page_unlock_tb(const TranslationBlock *tb) { }
> +static inline void tb_lock_pages(const TranslationBlock *tb) { }
>
> /*
> * For user-only, since we are protecting all of memory with a single lock,
> @@ -96,7 +86,7 @@ static void tb_remove_all(void)
> }
>
> /* Call with mmap_lock held. */
> -static void tb_record(TranslationBlock *tb, PageDesc *p1, PageDesc *p2)
> +static void tb_record(TranslationBlock *tb)
> {
> vaddr addr;
> int flags;
> @@ -391,12 +381,108 @@ static void page_lock(PageDesc *pd)
> qemu_spin_lock(&pd->lock);
> }
>
> +/* Like qemu_spin_trylock, returns false on success */
> +static bool page_trylock(PageDesc *pd)
> +{
> + bool busy = qemu_spin_trylock(&pd->lock);
> + if (!busy) {
> + page_lock__debug(pd);
> + }
> + return busy;
> +}
> +
> static void page_unlock(PageDesc *pd)
> {
> qemu_spin_unlock(&pd->lock);
> page_unlock__debug(pd);
> }
>
> +void tb_lock_page0(tb_page_addr_t paddr)
> +{
> + page_lock(page_find_alloc(paddr >> TARGET_PAGE_BITS, true));
> +}
> +
> +void tb_lock_page1(tb_page_addr_t paddr0, tb_page_addr_t paddr1)
> +{
> + tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
> + tb_page_addr_t pindex1 = paddr1 >> TARGET_PAGE_BITS;
> + PageDesc *pd0, *pd1;
> +
> + if (pindex0 == pindex1) {
> + /* Identical pages, and the first page is already locked. */
> + return;
> + }
> +
> + pd1 = page_find_alloc(pindex1, true);
> + if (pindex0 < pindex1) {
> + /* Correct locking order, we may block. */
> + page_lock(pd1);
> + return;
> + }
> +
> + /* Incorrect locking order, we cannot block lest we deadlock. */
> + if (!page_trylock(pd1)) {
> + return;
> + }
> +
> + /*
> + * Drop the lock on page0 and get both page locks in the right order.
> + * Restart translation via longjmp.
> + */
> + pd0 = page_find_alloc(pindex0, false);
> + page_unlock(pd0);
> + page_lock(pd1);
> + page_lock(pd0);
> + siglongjmp(tcg_ctx->jmp_trans, -3);
> +}
> +
> +void tb_unlock_page1(tb_page_addr_t paddr0, tb_page_addr_t paddr1)
> +{
> + tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
> + tb_page_addr_t pindex1 = paddr1 >> TARGET_PAGE_BITS;
> +
> + if (pindex0 != pindex1) {
> + page_unlock(page_find_alloc(pindex1, false));
> + }
> +}
> +
> +static void tb_lock_pages(TranslationBlock *tb)
> +{
> + tb_page_addr_t paddr0 = tb_page_addr0(tb);
> + tb_page_addr_t paddr1 = tb_page_addr1(tb);
> + tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
> + tb_page_addr_t pindex1 = paddr1 >> TARGET_PAGE_BITS;
> +
> + if (unlikely(paddr0 == -1)) {
> + return;
> + }
> + if (unlikely(paddr1 != -1) && pindex0 != pindex1) {
> + if (pindex0 < pindex1) {
> + page_lock(page_find_alloc(pindex0, true));
> + page_lock(page_find_alloc(pindex1, true));
> + return;
> + }
> + page_lock(page_find_alloc(pindex1, true));
> + }
> + page_lock(page_find_alloc(pindex0, true));
> +}
> +
> +void tb_unlock_pages(TranslationBlock *tb)
> +{
> + tb_page_addr_t paddr0 = tb_page_addr0(tb);
> + tb_page_addr_t paddr1 = tb_page_addr1(tb);
> + tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
> + tb_page_addr_t pindex1 = paddr1 >> TARGET_PAGE_BITS;
> +
> + if (unlikely(paddr0 == -1)) {
> + return;
> + }
> + if (unlikely(paddr1 != -1) && pindex0 != pindex1) {
> + page_unlock(page_find_alloc(pindex1, false));
> + }
> + page_unlock(page_find_alloc(pindex0, false));
> +}
> +
> static inline struct page_entry *
> page_entry_new(PageDesc *pd, tb_page_addr_t index)
> {
> @@ -420,13 +506,10 @@ static void page_entry_destroy(gpointer p)
> /* returns false on success */
> static bool page_entry_trylock(struct page_entry *pe)
> {
> - bool busy;
> -
> - busy = qemu_spin_trylock(&pe->pd->lock);
> + bool busy = page_trylock(pe->pd);
> if (!busy) {
> g_assert(!pe->locked);
> pe->locked = true;
> - page_lock__debug(pe->pd);
> }
> return busy;
> }
> @@ -604,8 +687,7 @@ static void tb_remove_all(void)
> * Add the tb in the target page and protect it if necessary.
> * Called with @p->lock held.
> */
> -static inline void tb_page_add(PageDesc *p, TranslationBlock *tb,
> - unsigned int n)
> +static void tb_page_add(PageDesc *p, TranslationBlock *tb, unsigned int n)
> {
> bool page_already_protected;
>
> @@ -625,15 +707,21 @@ static inline void tb_page_add(PageDesc *p,
> TranslationBlock *tb,
> }
> }
>
> -static void tb_record(TranslationBlock *tb, PageDesc *p1, PageDesc *p2)
> +static void tb_record(TranslationBlock *tb)
> {
> - tb_page_add(p1, tb, 0);
> - if (unlikely(p2)) {
> - tb_page_add(p2, tb, 1);
> + tb_page_addr_t paddr0 = tb_page_addr0(tb);
> + tb_page_addr_t paddr1 = tb_page_addr1(tb);
> + tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
> + tb_page_addr_t pindex1 = paddr0 >> TARGET_PAGE_BITS;
> +
> + assert(paddr0 != -1);
> + if (unlikely(paddr1 != -1) && pindex0 != pindex1) {
> + tb_page_add(page_find_alloc(pindex1, false), tb, 1);
> }
> + tb_page_add(page_find_alloc(pindex0, false), tb, 0);
> }
>
> -static inline void tb_page_remove(PageDesc *pd, TranslationBlock *tb)
> +static void tb_page_remove(PageDesc *pd, TranslationBlock *tb)
> {
> TranslationBlock *tb1;
> uintptr_t *pprev;
> @@ -653,74 +741,16 @@ static inline void tb_page_remove(PageDesc *pd,
> TranslationBlock *tb)
>
> static void tb_remove(TranslationBlock *tb)
> {
> - PageDesc *pd;
> + tb_page_addr_t paddr0 = tb_page_addr0(tb);
> + tb_page_addr_t paddr1 = tb_page_addr1(tb);
> + tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
> + tb_page_addr_t pindex1 = paddr0 >> TARGET_PAGE_BITS;
>
> - pd = page_find(tb->page_addr[0] >> TARGET_PAGE_BITS);
> - tb_page_remove(pd, tb);
> - if (unlikely(tb->page_addr[1] != -1)) {
> - pd = page_find(tb->page_addr[1] >> TARGET_PAGE_BITS);
> - tb_page_remove(pd, tb);
> - }
> -}
> -
> -static void page_lock_pair(PageDesc **ret_p1, tb_page_addr_t phys1,
> - PageDesc **ret_p2, tb_page_addr_t phys2, bool
> alloc)
> -{
> - PageDesc *p1, *p2;
> - tb_page_addr_t page1;
> - tb_page_addr_t page2;
> -
> - assert_memory_lock();
> - g_assert(phys1 != -1);
> -
> - page1 = phys1 >> TARGET_PAGE_BITS;
> - page2 = phys2 >> TARGET_PAGE_BITS;
> -
> - p1 = page_find_alloc(page1, alloc);
> - if (ret_p1) {
> - *ret_p1 = p1;
> - }
> - if (likely(phys2 == -1)) {
> - page_lock(p1);
> - return;
> - } else if (page1 == page2) {
> - page_lock(p1);
> - if (ret_p2) {
> - *ret_p2 = p1;
> - }
> - return;
> - }
> - p2 = page_find_alloc(page2, alloc);
> - if (ret_p2) {
> - *ret_p2 = p2;
> - }
> - if (page1 < page2) {
> - page_lock(p1);
> - page_lock(p2);
> - } else {
> - page_lock(p2);
> - page_lock(p1);
> - }
> -}
> -
> -/* lock the page(s) of a TB in the correct acquisition order */
> -static void page_lock_tb(const TranslationBlock *tb)
> -{
> - page_lock_pair(NULL, tb_page_addr0(tb), NULL, tb_page_addr1(tb), false);
> -}
> -
> -static void page_unlock_tb(const TranslationBlock *tb)
> -{
> - PageDesc *p1 = page_find(tb_page_addr0(tb) >> TARGET_PAGE_BITS);
> -
> - page_unlock(p1);
> - if (unlikely(tb_page_addr1(tb) != -1)) {
> - PageDesc *p2 = page_find(tb_page_addr1(tb) >> TARGET_PAGE_BITS);
> -
> - if (p2 != p1) {
> - page_unlock(p2);
> - }
> + assert(paddr0 != -1);
> + if (unlikely(paddr1 != -1) && pindex0 != pindex1) {
> + tb_page_remove(page_find_alloc(pindex1, false), tb);
> }
> + tb_page_remove(page_find_alloc(pindex0, false), tb);
> }
> #endif /* CONFIG_USER_ONLY */
>
> @@ -925,18 +955,16 @@ static void tb_phys_invalidate__locked(TranslationBlock
> *tb)
> void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr)
> {
> if (page_addr == -1 && tb_page_addr0(tb) != -1) {
> - page_lock_tb(tb);
> + tb_lock_pages(tb);
> do_tb_phys_invalidate(tb, true);
> - page_unlock_tb(tb);
> + tb_unlock_pages(tb);
> } else {
> do_tb_phys_invalidate(tb, false);
> }
> }
>
> /*
> - * Add a new TB and link it to the physical page tables. phys_page2 is
> - * (-1) to indicate that only one page contains the TB.
> - *
> + * Add a new TB and link it to the physical page tables.
> * Called with mmap_lock held for user-mode emulation.
> *
> * Returns a pointer @tb, or a pointer to an existing TB that matches @tb.
> @@ -944,43 +972,29 @@ void tb_phys_invalidate(TranslationBlock *tb,
> tb_page_addr_t page_addr)
> * for the same block of guest code that @tb corresponds to. In that case,
> * the caller should discard the original @tb, and use instead the returned
> TB.
> */
> -TranslationBlock *tb_link_page(TranslationBlock *tb, tb_page_addr_t phys_pc,
> - tb_page_addr_t phys_page2)
> +TranslationBlock *tb_link_page(TranslationBlock *tb)
> {
> - PageDesc *p;
> - PageDesc *p2 = NULL;
> void *existing_tb = NULL;
> uint32_t h;
>
> assert_memory_lock();
> tcg_debug_assert(!(tb->cflags & CF_INVALID));
>
> - /*
> - * Add the TB to the page list, acquiring first the pages's locks.
> - * We keep the locks held until after inserting the TB in the hash table,
> - * so that if the insertion fails we know for sure that the TBs are still
> - * in the page descriptors.
> - * Note that inserting into the hash table first isn't an option, since
> - * we can only insert TBs that are fully initialized.
> - */
> - page_lock_pair(&p, phys_pc, &p2, phys_page2, true);
> - tb_record(tb, p, p2);
> + tb_record(tb);
>
> /* add in the hash table */
> - h = tb_hash_func(phys_pc, (tb->cflags & CF_PCREL ? 0 : tb->pc),
> + h = tb_hash_func(tb_page_addr0(tb), (tb->cflags & CF_PCREL ? 0 : tb->pc),
> tb->flags, tb->cs_base, tb->cflags);
> qht_insert(&tb_ctx.htable, tb, h, &existing_tb);
>
> /* remove TB from the page(s) if we couldn't insert it */
> if (unlikely(existing_tb)) {
> tb_remove(tb);
> - tb = existing_tb;
> + tb_unlock_pages(tb);
> + return existing_tb;
> }
>
> - if (p2 && p2 != p) {
> - page_unlock(p2);
> - }
> - page_unlock(p);
> + tb_unlock_pages(tb);
> return tb;
> }
>
> diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
> index d3d4fbc1a4..4c17474fa2 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -290,7 +290,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> {
> CPUArchState *env = cpu->env_ptr;
> TranslationBlock *tb, *existing_tb;
> - tb_page_addr_t phys_pc;
> + tb_page_addr_t phys_pc, phys_p2;
> tcg_insn_unit *gen_code_buf;
> int gen_code_size, search_size, max_insns;
> int64_t ti;
> @@ -313,6 +313,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> QEMU_BUILD_BUG_ON(CF_COUNT_MASK + 1 != TCG_MAX_INSNS);
>
> buffer_overflow:
> + assert_no_pages_locked();
> tb = tcg_tb_alloc(tcg_ctx);
> if (unlikely(!tb)) {
> /* flush must be done */
> @@ -333,6 +334,10 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> tb->cflags = cflags;
> tb_set_page_addr0(tb, phys_pc);
> tb_set_page_addr1(tb, -1);
> + if (phys_pc != -1) {
> + tb_lock_page0(phys_pc);
> + }
> +
> tcg_ctx->gen_tb = tb;
> tcg_ctx->addr_type = TARGET_LONG_BITS == 32 ? TCG_TYPE_I32 :
> TCG_TYPE_I64;
> #ifdef CONFIG_SOFTMMU
> @@ -349,8 +354,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> tcg_ctx->guest_mo = TCG_MO_ALL;
> #endif
>
> - tb_overflow:
> -
> + restart_translate:
> trace_translate_block(tb, pc, tb->tc.ptr);
>
> gen_code_size = setjmp_gen_code(env, tb, pc, host_pc, &max_insns, &ti);
> @@ -369,6 +373,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> qemu_log_mask(CPU_LOG_TB_OP | CPU_LOG_TB_OP_OPT,
> "Restarting code generation for "
> "code_gen_buffer overflow\n");
> + tb_unlock_pages(tb);
> goto buffer_overflow;
>
> case -2:
> @@ -387,14 +392,39 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> "Restarting code generation with "
> "smaller translation block (max %d insns)\n",
> max_insns);
> - goto tb_overflow;
> +
> + /*
> + * The half-sized TB may not cross pages.
> + * TODO: Fix all targets that cross pages except with
> + * the first insn, at which point this can't be reached.
> + */
> + phys_p2 = tb_page_addr1(tb);
> + if (unlikely(phys_p2 != -1)) {
> + tb_unlock_page1(phys_pc, phys_p2);
> + tb_set_page_addr1(tb, -1);
> + }
> + goto restart_translate;
> +
> + case -3:
> + /*
> + * We had a page lock ordering problem. In order to avoid
> + * deadlock we had to drop the lock on page0, which means
> + * that everything we translated so far is compromised.
> + * Restart with locks held on both pages.
> + */
> + qemu_log_mask(CPU_LOG_TB_OP | CPU_LOG_TB_OP_OPT,
> + "Restarting code generation with re-locked pages");
> + goto restart_translate;
>
> default:
> g_assert_not_reached();
> }
> }
> + tcg_ctx->gen_tb = NULL;
> +
> search_size = encode_search(tb, (void *)gen_code_buf + gen_code_size);
> if (unlikely(search_size < 0)) {
> + tb_unlock_pages(tb);
> goto buffer_overflow;
> }
> tb->tc.size = gen_code_size;
> @@ -504,6 +534,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> * before attempting to link to other TBs or add to the lookup table.
> */
> if (tb_page_addr0(tb) == -1) {
> + assert_no_pages_locked();
> return tb;
> }
>
> @@ -518,7 +549,9 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
> * No explicit memory barrier is required -- tb_link_page() makes the
> * TB visible in a consistent state.
> */
> - existing_tb = tb_link_page(tb, tb_page_addr0(tb), tb_page_addr1(tb));
> + existing_tb = tb_link_page(tb);
> + assert_no_pages_locked();
> +
> /* if the TB already exists, discard what we just translated */
> if (unlikely(existing_tb != tb)) {
> uintptr_t orig_aligned = (uintptr_t)gen_code_buf;
> diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
> index 0fd9efceba..1a6a5448c8 100644
> --- a/accel/tcg/translator.c
> +++ b/accel/tcg/translator.c
> @@ -12,9 +12,9 @@
> #include "qemu/error-report.h"
> #include "exec/exec-all.h"
> #include "exec/translator.h"
> -#include "exec/translate-all.h"
> #include "exec/plugin-gen.h"
> #include "tcg/tcg-op-common.h"
> +#include "internal.h"
>
> static void gen_io_start(void)
> {
> @@ -147,10 +147,6 @@ void translator_loop(CPUState *cpu, TranslationBlock
> *tb, int *max_insns,
> db->host_addr[0] = host_pc;
> db->host_addr[1] = NULL;
>
> -#ifdef CONFIG_USER_ONLY
> - page_protect(pc);
> -#endif
> -
> ops->init_disas_context(db, cpu);
> tcg_debug_assert(db->is_jmp == DISAS_NEXT); /* no early exit */
>
> @@ -256,22 +252,36 @@ static void *translator_access(CPUArchState *env,
> DisasContextBase *db,
> host = db->host_addr[1];
> base = TARGET_PAGE_ALIGN(db->pc_first);
> if (host == NULL) {
> - tb_page_addr_t phys_page =
> - get_page_addr_code_hostp(env, base, &db->host_addr[1]);
> + tb_page_addr_t page0, old_page1, new_page1;
> +
> + new_page1 = get_page_addr_code_hostp(env, base,
> &db->host_addr[1]);
>
> /*
> * If the second page is MMIO, treat as if the first page
> * was MMIO as well, so that we do not cache the TB.
> */
> - if (unlikely(phys_page == -1)) {
> + if (unlikely(new_page1 == -1)) {
> + tb_unlock_pages(tb);
> tb_set_page_addr0(tb, -1);
> return NULL;
> }
>
> - tb_set_page_addr1(tb, phys_page);
> -#ifdef CONFIG_USER_ONLY
> - page_protect(end);
> -#endif
> + /*
> + * If this is not the first time around, and page1 matches,
> + * then we already have the page locked. Alternately, we're
> + * not doing anything to prevent the PTE from changing, so
> + * we might wind up with a different page, requiring us to
> + * re-do the locking.
> + */
> + old_page1 = tb_page_addr1(tb);
> + if (likely(new_page1 != old_page1)) {
> + page0 = tb_page_addr0(tb);
> + if (unlikely(old_page1 != -1)) {
> + tb_unlock_page1(page0, old_page1);
> + }
> + tb_set_page_addr1(tb, new_page1);
> + tb_lock_page1(page0, new_page1);
> + }
> host = db->host_addr[1];
> }
>
> --
> 2.34.1
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v
