target/i386: Add tcg/access.[ch]

Provide a method to amortize page lookup across large blocks.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/i386/tcg/access.c

@@ -0,0 +1,169 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Access guest memory in blocks. */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "exec/cpu_ldst.h"
+#include "exec/exec-all.h"
+#include "access.h"
+
+
+void access_prepare_mmu(X86Access *ret, CPUX86State *env,
+                        vaddr vaddr, unsigned size,
+                        MMUAccessType type, int mmu_idx, uintptr_t ra)
+{
+    int size1, size2;
+    void *haddr1, *haddr2;
+
+    assert(size > 0 && size <= TARGET_PAGE_SIZE);
+
+    size1 = MIN(size, -(vaddr | TARGET_PAGE_MASK)),
+    size2 = size - size1;
+
+    memset(ret, 0, sizeof(*ret));
+    ret->vaddr = vaddr;
+    ret->size = size;
+    ret->size1 = size1;
+    ret->mmu_idx = mmu_idx;
+    ret->env = env;
+    ret->ra = ra;
+
+    haddr1 = probe_access(env, vaddr, size1, type, mmu_idx, ra);
+    ret->haddr1 = haddr1;
+
+    if (unlikely(size2)) {
+        haddr2 = probe_access(env, vaddr + size1, size2, type, mmu_idx, ra);
+        if (haddr2 == haddr1 + size1) {
+            ret->size1 = size;
+        } else {
+#ifdef CONFIG_USER_ONLY
+            g_assert_not_reached();
+#else
+            ret->haddr2 = haddr2;
+#endif
+        }
+    }
+}
+
+void access_prepare(X86Access *ret, CPUX86State *env, vaddr vaddr,
+                    unsigned size, MMUAccessType type, uintptr_t ra)
+{
+    int mmu_idx = cpu_mmu_index(env_cpu(env), false);
+    access_prepare_mmu(ret, env, vaddr, size, type, mmu_idx, ra);
+}
+
+static void *access_ptr(X86Access *ac, vaddr addr, unsigned len)
+{
+    vaddr offset = addr - ac->vaddr;
+
+    assert(addr >= ac->vaddr);
+
+#ifdef CONFIG_USER_ONLY
+    assert(offset <= ac->size1 - len);
+    return ac->haddr1 + offset;
+#else
+    if (likely(offset <= ac->size1 - len)) {
+        return ac->haddr1 + offset;
+    }
+    assert(offset <= ac->size - len);
+    /*
+     * If the address is not naturally aligned, it might span both pages.
+     * Only return ac->haddr2 if the area is entirely within the second page,
+     * otherwise fall back to slow accesses.
+     */
+    if (likely(offset >= ac->size1)) {
+        return ac->haddr2 + (offset - ac->size1);
+    }
+    return NULL;
+#endif
+}
+
+#ifdef CONFIG_USER_ONLY
+# define test_ptr(p)  true
+#else
+# define test_ptr(p)  likely(p)
+#endif
+
+uint8_t access_ldb(X86Access *ac, vaddr addr)
+{
+    void *p = access_ptr(ac, addr, sizeof(uint8_t));
+
+    if (test_ptr(p)) {
+        return ldub_p(p);
+    }
+    return cpu_ldub_mmuidx_ra(ac->env, addr, ac->mmu_idx, ac->ra);
+}
+
+uint16_t access_ldw(X86Access *ac, vaddr addr)
+{
+    void *p = access_ptr(ac, addr, sizeof(uint16_t));
+
+    if (test_ptr(p)) {
+        return lduw_le_p(p);
+    }
+    return cpu_lduw_le_mmuidx_ra(ac->env, addr, ac->mmu_idx, ac->ra);
+}
+
+uint32_t access_ldl(X86Access *ac, vaddr addr)
+{
+    void *p = access_ptr(ac, addr, sizeof(uint32_t));
+
+    if (test_ptr(p)) {
+        return ldl_le_p(p);
+    }
+    return cpu_ldl_le_mmuidx_ra(ac->env, addr, ac->mmu_idx, ac->ra);
+}
+
+uint64_t access_ldq(X86Access *ac, vaddr addr)
+{
+    void *p = access_ptr(ac, addr, sizeof(uint64_t));
+
+    if (test_ptr(p)) {
+        return ldq_le_p(p);
+    }
+    return cpu_ldq_le_mmuidx_ra(ac->env, addr, ac->mmu_idx, ac->ra);
+}
+
+void access_stb(X86Access *ac, vaddr addr, uint8_t val)
+{
+    void *p = access_ptr(ac, addr, sizeof(uint8_t));
+
+    if (test_ptr(p)) {
+        stb_p(p, val);
+    } else {
+        cpu_stb_mmuidx_ra(ac->env, addr, val, ac->mmu_idx, ac->ra);
+    }
+}
+
+void access_stw(X86Access *ac, vaddr addr, uint16_t val)
+{
+    void *p = access_ptr(ac, addr, sizeof(uint16_t));
+
+    if (test_ptr(p)) {
+        stw_le_p(p, val);
+    } else {
+        cpu_stw_le_mmuidx_ra(ac->env, addr, val, ac->mmu_idx, ac->ra);
+    }
+}
+
+void access_stl(X86Access *ac, vaddr addr, uint32_t val)
+{
+    void *p = access_ptr(ac, addr, sizeof(uint32_t));
+
+    if (test_ptr(p)) {
+        stl_le_p(p, val);
+    } else {
+        cpu_stl_le_mmuidx_ra(ac->env, addr, val, ac->mmu_idx, ac->ra);
+    }
+}
+
+void access_stq(X86Access *ac, vaddr addr, uint64_t val)
+{
+    void *p = access_ptr(ac, addr, sizeof(uint64_t));
+
+    if (test_ptr(p)) {
+        stq_le_p(p, val);
+    } else {
+        cpu_stq_le_mmuidx_ra(ac->env, addr, val, ac->mmu_idx, ac->ra);
+    }
+}

target/i386/tcg/access.h

@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Access guest memory in blocks. */
+
+#ifndef X86_TCG_ACCESS_H
+#define X86_TCG_ACCESS_H
+
+/* An access covers at most sizeof(X86XSaveArea), at most 2 pages. */
+typedef struct X86Access {
+    target_ulong vaddr;
+    void *haddr1;
+    void *haddr2;
+    uint16_t size;
+    uint16_t size1;
+    /*
+     * If we can't access the host page directly, we'll have to do I/O access
+     * via ld/st helpers. These are internal details, so we store the rest
+     * to do the access here instead of passing it around in the helpers.
+     */
+    int mmu_idx;
+    CPUX86State *env;
+    uintptr_t ra;
+} X86Access;
+
+void access_prepare_mmu(X86Access *ret, CPUX86State *env,
+                        vaddr vaddr, unsigned size,
+                        MMUAccessType type, int mmu_idx, uintptr_t ra);
+void access_prepare(X86Access *ret, CPUX86State *env, vaddr vaddr,
+                    unsigned size, MMUAccessType type, uintptr_t ra);
+
+uint8_t  access_ldb(X86Access *ac, vaddr addr);
+uint16_t access_ldw(X86Access *ac, vaddr addr);
+uint32_t access_ldl(X86Access *ac, vaddr addr);
+uint64_t access_ldq(X86Access *ac, vaddr addr);
+
+void access_stb(X86Access *ac, vaddr addr, uint8_t val);
+void access_stw(X86Access *ac, vaddr addr, uint16_t val);
+void access_stl(X86Access *ac, vaddr addr, uint32_t val);
+void access_stq(X86Access *ac, vaddr addr, uint64_t val);
+
+#endif

target/i386/tcg/meson.build

@@ -1,4 +1,5 @@
 i386_ss.add(when: 'CONFIG_TCG', if_true: files(
+  'access.c',
   'bpt_helper.c',
   'cc_helper.c',
   'excp_helper.c',