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[PATCH 14/14] target/i386: Use atomic operations for pte updates
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From: |
Richard Henderson |
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Subject: |
[PATCH 14/14] target/i386: Use atomic operations for pte updates |
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Date: |
Mon, 22 Aug 2022 16:58:03 -0700 |
Use probe_access_full in order to resolve to a host address,
which then lets us use a host cmpxchg to update the pte.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/279
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
target/i386/tcg/sysemu/excp_helper.c | 242 +++++++++++++++++++--------
1 file changed, 168 insertions(+), 74 deletions(-)
diff --git a/target/i386/tcg/sysemu/excp_helper.c
b/target/i386/tcg/sysemu/excp_helper.c
index e5d9ff138e..74a76cf883 100644
--- a/target/i386/tcg/sysemu/excp_helper.c
+++ b/target/i386/tcg/sysemu/excp_helper.c
@@ -27,8 +27,8 @@ typedef struct TranslateParams {
target_ulong cr3;
int pg_mode;
int mmu_idx;
+ int ptw_idx;
MMUAccessType access_type;
- bool use_stage2;
} TranslateParams;
typedef struct TranslateResult {
@@ -50,43 +50,106 @@ typedef struct TranslateFault {
TranslateFaultStage2 stage2;
} TranslateFault;
-#define PTE_HPHYS(ADDR) \
- do { \
- if (in->use_stage2) { \
- nested_in.addr = (ADDR); \
- if (!mmu_translate(env, &nested_in, out, err)) { \
- err->stage2 = S2_GPT; \
- return false; \
- } \
- (ADDR) = out->paddr; \
- } \
- } while (0)
+typedef struct PTETranslate {
+ CPUX86State *env;
+ TranslateFault *err;
+ int ptw_idx;
+ void *haddr;
+ hwaddr gaddr;
+} PTETranslate;
+
+static bool ptw_translate(PTETranslate *inout, hwaddr addr)
+{
+ CPUTLBEntryFull *full;
+ int flags;
+
+ inout->gaddr = addr;
+ flags = probe_access_full(inout->env, addr, MMU_DATA_STORE,
+ inout->ptw_idx, true, &inout->haddr, &full, 0);
+
+ if (unlikely(flags & TLB_INVALID_MASK)) {
+ TranslateFault *err = inout->err;
+
+ assert(inout->ptw_idx == MMU_NESTED_IDX);
+ err->exception_index = 0; /* unused */
+ err->error_code = inout->env->error_code;
+ err->cr2 = addr;
+ err->stage2 = S2_GPT;
+ return false;
+ }
+ return true;
+}
+
+static inline uint32_t ptw_ldl(const PTETranslate *in)
+{
+ if (likely(in->haddr)) {
+ return ldl_p(in->haddr);
+ }
+ return cpu_ldl_mmuidx_ra(in->env, in->gaddr, in->ptw_idx, 0);
+}
+
+static inline uint64_t ptw_ldq(const PTETranslate *in)
+{
+ if (likely(in->haddr)) {
+ return ldq_p(in->haddr);
+ }
+ return cpu_ldq_mmuidx_ra(in->env, in->gaddr, in->ptw_idx, 0);
+}
+
+/*
+ * Note that we can use a 32-bit cmpxchg for all page table entries,
+ * even 64-bit ones, because PG_PRESENT_MASK, PG_ACCESSED_MASK and
+ * PG_DIRTY_MASK are all in the low 32 bits.
+ */
+static bool ptw_setl_slow(const PTETranslate *in, uint32_t old, uint32_t new)
+{
+ uint32_t cmp;
+
+ /* Does x86 really perform a rmw cycle on mmio for ptw? */
+ start_exclusive();
+ cmp = cpu_ldl_mmuidx_ra(in->env, in->gaddr, in->ptw_idx, 0);
+ if (cmp == old) {
+ cpu_stl_mmuidx_ra(in->env, in->gaddr, new, in->ptw_idx, 0);
+ }
+ end_exclusive();
+ return cmp == old;
+}
+
+static inline bool ptw_setl(const PTETranslate *in, uint32_t old, uint32_t set)
+{
+ if (set & ~old) {
+ uint32_t new = old | set;
+ if (likely(in->haddr)) {
+ old = cpu_to_le32(old);
+ new = cpu_to_le32(new);
+ return qatomic_cmpxchg((uint32_t *)in->haddr, old, new) == old;
+ }
+ return ptw_setl_slow(in, old, new);
+ }
+ return true;
+}
static bool mmu_translate(CPUX86State *env, const TranslateParams *in,
TranslateResult *out, TranslateFault *err)
{
- TranslateParams nested_in = {
- /* Use store for page table entries, to allow A/D flag updates. */
- .access_type = MMU_DATA_STORE,
- .cr3 = env->nested_cr3,
- .pg_mode = env->nested_pg_mode,
- .mmu_idx = MMU_USER_IDX,
- .use_stage2 = false,
- };
-
- CPUState *cs = env_cpu(env);
- X86CPU *cpu = env_archcpu(env);
const int32_t a20_mask = x86_get_a20_mask(env);
const target_ulong addr = in->addr;
const int pg_mode = in->pg_mode;
const bool is_user = (in->mmu_idx == MMU_USER_IDX);
const MMUAccessType access_type = in->access_type;
- uint64_t ptep, pte;
+ uint64_t ptep, pte, rsvd_mask;
+ PTETranslate pte_trans = {
+ .env = env,
+ .err = err,
+ .ptw_idx = in->ptw_idx,
+ };
hwaddr pte_addr;
- uint64_t rsvd_mask = PG_ADDRESS_MASK & ~MAKE_64BIT_MASK(0, cpu->phys_bits);
uint32_t pkr;
int page_size;
+ restart_all:
+ rsvd_mask = ~MAKE_64BIT_MASK(0, env_archcpu(env)->phys_bits);
+ rsvd_mask &= PG_ADDRESS_MASK;
if (!(pg_mode & PG_MODE_NXE)) {
rsvd_mask |= PG_NX_MASK;
}
@@ -100,17 +163,19 @@ static bool mmu_translate(CPUX86State *env, const
TranslateParams *in,
*/
pte_addr = ((in->cr3 & ~0xfff) +
(((addr >> 48) & 0x1ff) << 3)) & a20_mask;
- PTE_HPHYS(pte_addr);
- pte = x86_ldq_phys(cs, pte_addr);
+ if (!ptw_translate(&pte_trans, pte_addr)) {
+ return false;
+ }
+ restart_5:
+ pte = ptw_ldq(&pte_trans);
if (!(pte & PG_PRESENT_MASK)) {
goto do_fault;
}
if (pte & (rsvd_mask | PG_PSE_MASK)) {
goto do_fault_rsvd;
}
- if (!(pte & PG_ACCESSED_MASK)) {
- pte |= PG_ACCESSED_MASK;
- x86_stl_phys_notdirty(cs, pte_addr, pte);
+ if (!ptw_setl(&pte_trans, pte, PG_ACCESSED_MASK)) {
+ goto restart_5;
}
ptep = pte ^ PG_NX_MASK;
} else {
@@ -123,17 +188,19 @@ static bool mmu_translate(CPUX86State *env, const
TranslateParams *in,
*/
pte_addr = ((pte & PG_ADDRESS_MASK) +
(((addr >> 39) & 0x1ff) << 3)) & a20_mask;
- PTE_HPHYS(pte_addr);
- pte = x86_ldq_phys(cs, pte_addr);
+ if (!ptw_translate(&pte_trans, pte_addr)) {
+ return false;
+ }
+ restart_4:
+ pte = ptw_ldq(&pte_trans);
if (!(pte & PG_PRESENT_MASK)) {
goto do_fault;
}
if (pte & (rsvd_mask | PG_PSE_MASK)) {
goto do_fault_rsvd;
}
- if (!(pte & PG_ACCESSED_MASK)) {
- pte |= PG_ACCESSED_MASK;
- x86_stl_phys_notdirty(cs, pte_addr, pte);
+ if (!ptw_setl(&pte_trans, pte, PG_ACCESSED_MASK)) {
+ goto restart_4;
}
ptep &= pte ^ PG_NX_MASK;
@@ -142,19 +209,21 @@ static bool mmu_translate(CPUX86State *env, const
TranslateParams *in,
*/
pte_addr = ((pte & PG_ADDRESS_MASK) +
(((addr >> 30) & 0x1ff) << 3)) & a20_mask;
- PTE_HPHYS(pte_addr);
- pte = x86_ldq_phys(cs, pte_addr);
+ if (!ptw_translate(&pte_trans, pte_addr)) {
+ return false;
+ }
+ restart_3_lma:
+ pte = ptw_ldq(&pte_trans);
if (!(pte & PG_PRESENT_MASK)) {
goto do_fault;
}
if (pte & rsvd_mask) {
goto do_fault_rsvd;
}
- ptep &= pte ^ PG_NX_MASK;
- if (!(pte & PG_ACCESSED_MASK)) {
- pte |= PG_ACCESSED_MASK;
- x86_stl_phys_notdirty(cs, pte_addr, pte);
+ if (!ptw_setl(&pte_trans, pte, PG_ACCESSED_MASK)) {
+ goto restart_3_lma;
}
+ ptep &= pte ^ PG_NX_MASK;
if (pte & PG_PSE_MASK) {
/* 1 GB page */
page_size = 1024 * 1024 * 1024;
@@ -167,15 +236,21 @@ static bool mmu_translate(CPUX86State *env, const
TranslateParams *in,
* Page table level 3
*/
pte_addr = ((in->cr3 & ~0x1f) + ((addr >> 27) & 0x18)) & a20_mask;
- PTE_HPHYS(pte_addr);
- pte = x86_ldq_phys(cs, pte_addr);
+ if (!ptw_translate(&pte_trans, pte_addr)) {
+ return false;
+ }
+ rsvd_mask |= PG_HI_USER_MASK;
+ restart_3_nolma:
+ pte = ptw_ldq(&pte_trans);
if (!(pte & PG_PRESENT_MASK)) {
goto do_fault;
}
- rsvd_mask |= PG_HI_USER_MASK;
if (pte & (rsvd_mask | PG_NX_MASK)) {
goto do_fault_rsvd;
}
+ if (!ptw_setl(&pte_trans, pte, PG_ACCESSED_MASK)) {
+ goto restart_3_nolma;
+ }
ptep = PG_NX_MASK | PG_USER_MASK | PG_RW_MASK;
}
@@ -184,32 +259,37 @@ static bool mmu_translate(CPUX86State *env, const
TranslateParams *in,
*/
pte_addr = ((pte & PG_ADDRESS_MASK) +
(((addr >> 21) & 0x1ff) << 3)) & a20_mask;
- PTE_HPHYS(pte_addr);
- pte = x86_ldq_phys(cs, pte_addr);
+ if (!ptw_translate(&pte_trans, pte_addr)) {
+ return false;
+ }
+ restart_2_pae:
+ pte = ptw_ldq(&pte_trans);
if (!(pte & PG_PRESENT_MASK)) {
goto do_fault;
}
if (pte & rsvd_mask) {
goto do_fault_rsvd;
}
- ptep &= pte ^ PG_NX_MASK;
if (pte & PG_PSE_MASK) {
/* 2 MB page */
page_size = 2048 * 1024;
+ ptep &= pte ^ PG_NX_MASK;
goto do_check_protect;
}
- if (!(pte & PG_ACCESSED_MASK)) {
- pte |= PG_ACCESSED_MASK;
- x86_stl_phys_notdirty(cs, pte_addr, pte);
+ if (!ptw_setl(&pte_trans, pte, PG_ACCESSED_MASK)) {
+ goto restart_2_pae;
}
+ ptep &= pte ^ PG_NX_MASK;
/*
* Page table level 1
*/
pte_addr = ((pte & PG_ADDRESS_MASK) +
(((addr >> 12) & 0x1ff) << 3)) & a20_mask;
- PTE_HPHYS(pte_addr);
- pte = x86_ldq_phys(cs, pte_addr);
+ if (!ptw_translate(&pte_trans, pte_addr)) {
+ return false;
+ }
+ pte = ptw_ldq(&pte_trans);
if (!(pte & PG_PRESENT_MASK)) {
goto do_fault;
}
@@ -224,8 +304,11 @@ static bool mmu_translate(CPUX86State *env, const
TranslateParams *in,
* Page table level 2
*/
pte_addr = ((in->cr3 & ~0xfff) + ((addr >> 20) & 0xffc)) & a20_mask;
- PTE_HPHYS(pte_addr);
- pte = x86_ldl_phys(cs, pte_addr);
+ if (!ptw_translate(&pte_trans, pte_addr)) {
+ return false;
+ }
+ restart_2_nopae:
+ pte = ptw_ldl(&pte_trans);
if (!(pte & PG_PRESENT_MASK)) {
goto do_fault;
}
@@ -242,17 +325,18 @@ static bool mmu_translate(CPUX86State *env, const
TranslateParams *in,
rsvd_mask = 0x200000;
goto do_check_protect_pse36;
}
- if (!(pte & PG_ACCESSED_MASK)) {
- pte |= PG_ACCESSED_MASK;
- x86_stl_phys_notdirty(cs, pte_addr, pte);
+ if (!ptw_setl(&pte_trans, pte, PG_ACCESSED_MASK)) {
+ goto restart_2_nopae;
}
/*
* Page table level 1
*/
pte_addr = ((pte & ~0xfffu) + ((addr >> 10) & 0xffc)) & a20_mask;
- PTE_HPHYS(pte_addr);
- pte = x86_ldl_phys(cs, pte_addr);
+ if (!ptw_translate(&pte_trans, pte_addr)) {
+ return false;
+ }
+ pte = ptw_ldl(&pte_trans);
if (!(pte & PG_PRESENT_MASK)) {
goto do_fault;
}
@@ -319,27 +403,35 @@ do_check_protect_pse36:
uint32_t set = PG_ACCESSED_MASK;
if (access_type == MMU_DATA_STORE) {
set |= PG_DIRTY_MASK;
+ } else if (!(pte & PG_DIRTY_MASK)) {
+ /*
+ * Only set write access if already dirty...
+ * otherwise wait for dirty access.
+ */
+ prot &= ~PAGE_WRITE;
}
- if (set & ~pte) {
- pte |= set;
- x86_stl_phys_notdirty(cs, pte_addr, pte);
+ if (!ptw_setl(&pte_trans, pte, set)) {
+ /*
+ * We can arrive here from any of 3 levels and 2 formats.
+ * The only safe thing is to restart the entire lookup.
+ */
+ goto restart_all;
}
}
- if (!(pte & PG_DIRTY_MASK)) {
- /* only set write access if already dirty... otherwise wait
- for dirty access */
- assert(access_type != MMU_DATA_STORE);
- prot &= ~PAGE_WRITE;
- }
-
/* align to page_size */
out->paddr = (pte & a20_mask & PG_ADDRESS_MASK & ~(page_size - 1))
| (addr & (page_size - 1));
- if (in->use_stage2) {
- nested_in.addr = out->paddr;
- nested_in.access_type = access_type;
+ if (in->ptw_idx == MMU_NESTED_IDX) {
+ TranslateParams nested_in = {
+ .addr = out->paddr,
+ .access_type = access_type,
+ .cr3 = env->nested_cr3,
+ .pg_mode = env->nested_pg_mode,
+ .mmu_idx = MMU_USER_IDX,
+ .ptw_idx = MMU_PHYS_IDX,
+ };
if (!mmu_translate(env, &nested_in, out, err)) {
err->stage2 = S2_GPA;
@@ -436,7 +528,7 @@ static bool get_physical_address(CPUX86State *env, vaddr
addr,
in.cr3 = env->nested_cr3;
in.pg_mode = env->nested_pg_mode;
in.mmu_idx = MMU_USER_IDX;
- in.use_stage2 = false;
+ in.ptw_idx = MMU_PHYS_IDX;
if (!mmu_translate(env, &in, out, err)) {
err->stage2 = S2_GPA;
@@ -449,7 +541,7 @@ static bool get_physical_address(CPUX86State *env, vaddr
addr,
default:
in.cr3 = env->cr[3];
in.mmu_idx = mmu_idx;
- in.use_stage2 = use_stage2;
+ in.ptw_idx = use_stage2 ? MMU_NESTED_IDX : MMU_PHYS_IDX;
in.pg_mode = get_pg_mode(env);
if (likely(in.pg_mode)) {
@@ -504,6 +596,8 @@ bool x86_cpu_tlb_fill(CPUState *cs, vaddr addr, int size,
}
if (probe) {
+ /* This will be used if recursing for stage2 translation. */
+ env->error_code = err.error_code;
return false;
}
--
2.34.1
- [PATCH 00/14] target/i386: Use atomic operations for pte updates, Richard Henderson, 2022/08/22
- [PATCH 01/14] accel/tcg: Rename CPUIOTLBEntry to CPUTLBEntryFull, Richard Henderson, 2022/08/22
- [PATCH 02/14] accel/tcg: Drop addr member from SavedIOTLB, Richard Henderson, 2022/08/22
- [PATCH 04/14] accel/tcg: Introduce probe_access_full, Richard Henderson, 2022/08/22
- [PATCH 06/14] include/exec: Introduce TARGET_PAGE_ENTRY_EXTRA, Richard Henderson, 2022/08/22
- [PATCH 03/14] accel/tcg: Suppress auto-invalidate in probe_access_internal, Richard Henderson, 2022/08/22
- [PATCH 05/14] accel/tcg: Introduce tlb_set_page_full, Richard Henderson, 2022/08/22
- [PATCH 08/14] target/i386: Direct call get_hphys from mmu_translate, Richard Henderson, 2022/08/22
- [PATCH 07/14] target/i386: Use MMUAccessType across excp_helper.c, Richard Henderson, 2022/08/22
- [PATCH 14/14] target/i386: Use atomic operations for pte updates,
Richard Henderson <=
- [PATCH 11/14] target/i386: Add MMU_PHYS_IDX and MMU_NESTED_IDX, Richard Henderson, 2022/08/22
- [PATCH 10/14] target/i386: Reorg GET_HPHYS, Richard Henderson, 2022/08/22
- [PATCH 09/14] target/i386: Introduce structures for mmu_translate, Richard Henderson, 2022/08/22
- [PATCH 13/14] target/i386: Combine 5 sets of variables in mmu_translate, Richard Henderson, 2022/08/22
- [PATCH 12/14] target/i386: Use MMU_NESTED_IDX for vmload/vmsave, Richard Henderson, 2022/08/22
- Re: [PATCH 00/14] target/i386: Use atomic operations for pte updates, Richard Henderson, 2022/08/22