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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v4 19/20] x86/shadow: fully move unmap-dest into common code
By adding guest PTE size to shadow emulation context, the work begun by
commit 2c80710a78 ("x86/shadow: compile most write emulation code just
once") can be completed, paving the road for further movement into
common code.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
v4: Adjust comment style in moved code.
v3: New.
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -319,7 +319,8 @@ static const struct x86_emulate_ops hvm_
};
const struct x86_emulate_ops *shadow_init_emulation(
- struct sh_emulate_ctxt *sh_ctxt, struct cpu_user_regs *regs)
+ struct sh_emulate_ctxt *sh_ctxt, struct cpu_user_regs *regs,
+ unsigned int pte_size)
{
struct segment_register *creg, *sreg;
struct vcpu *v = current;
@@ -346,6 +347,8 @@ const struct x86_emulate_ops *shadow_ini
sh_ctxt->ctxt.sp_size = sreg->db ? 32 : 16;
}
+ sh_ctxt->pte_size = pte_size;
+
/* Attempt to prefetch whole instruction. */
sh_ctxt->insn_buf_eip = regs->rip;
sh_ctxt->insn_buf_bytes =
@@ -1769,6 +1772,45 @@ void *sh_emulate_map_dest(struct vcpu *v
return map;
}
+/*
+ * Optimization: If we see two emulated writes of zeros to the same
+ * page-table without another kind of page fault in between, we guess
+ * that this is a batch of changes (for process destruction) and
+ * unshadow the page so we don't take a pagefault on every entry. This
+ * should also make finding writeable mappings of pagetables much
+ * easier.
+ *
+ * Look to see if this is the second emulated write in a row to this
+ * page, and unshadow if it is.
+ */
+static inline void check_for_early_unshadow(struct vcpu *v, mfn_t gmfn)
+{
+#if SHADOW_OPTIMIZATIONS & SHOPT_EARLY_UNSHADOW
+ struct domain *d = v->domain;
+
+ /*
+ * If the domain has never made a "dying" op, use the two-writes
+ * heuristic; otherwise, unshadow as soon as we write a zero for a dying
+ * process.
+ *
+ * Don't bother trying to unshadow if it's not a PT, or if it's > l1.
+ */
+ if ( ( v->arch.paging.shadow.pagetable_dying
+ || ( !d->arch.paging.shadow.pagetable_dying_op
+ && v->arch.paging.shadow.last_emulated_mfn_for_unshadow ==
mfn_x(gmfn) ) )
+ && sh_mfn_is_a_page_table(gmfn)
+ && (!d->arch.paging.shadow.pagetable_dying_op ||
+ !(mfn_to_page(gmfn)->shadow_flags
+ & (SHF_L2_32|SHF_L2_PAE|SHF_L2H_PAE|SHF_L4_64))) )
+ {
+ perfc_incr(shadow_early_unshadow);
+ sh_remove_shadows(d, gmfn, 1, 0 /* Fast, can fail to unshadow */ );
+ TRACE_SHADOW_PATH_FLAG(TRCE_SFLAG_EARLY_UNSHADOW);
+ }
+ v->arch.paging.shadow.last_emulated_mfn_for_unshadow = mfn_x(gmfn);
+#endif
+}
+
/*
* Tidy up after the emulated write: mark pages dirty, verify the new
* contents, and undo the mapping.
@@ -1778,6 +1817,21 @@ void sh_emulate_unmap_dest(struct vcpu *
{
u32 b1 = bytes, b2 = 0, shflags;
+ ASSERT(mfn_valid(sh_ctxt->mfn[0]));
+
+ /* If we are writing lots of PTE-aligned zeros, might want to unshadow */
+ if ( likely(bytes >= 4) && (*(u32 *)addr == 0) )
+ {
+ if ( !((unsigned long)addr & (sh_ctxt->pte_size - 1)) )
+ check_for_early_unshadow(v, sh_ctxt->mfn[0]);
+ /*
+ * Don't reset the heuristic if we're writing zeros at non-aligned
+ * addresses, otherwise it doesn't catch REP MOVSD on PAE guests.
+ */
+ }
+ else
+ sh_reset_early_unshadow(v);
+
/*
* We can avoid re-verifying the page contents after the write if:
* - it was no larger than the PTE type of this pagetable;
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -2533,52 +2533,6 @@ sh_map_and_validate_gl1e(struct vcpu *v,
/**************************************************************************/
-/* Optimization: If we see two emulated writes of zeros to the same
- * page-table without another kind of page fault in between, we guess
- * that this is a batch of changes (for process destruction) and
- * unshadow the page so we don't take a pagefault on every entry. This
- * should also make finding writeable mappings of pagetables much
- * easier. */
-
-/* Look to see if this is the second emulated write in a row to this
- * page, and unshadow if it is */
-static inline void check_for_early_unshadow(struct vcpu *v, mfn_t gmfn)
-{
-#if SHADOW_OPTIMIZATIONS & SHOPT_EARLY_UNSHADOW
- struct domain *d = v->domain;
- /* If the domain has never made a "dying" op, use the two-writes
- * heuristic; otherwise, unshadow as soon as we write a zero for a dying
- * process.
- *
- * Don't bother trying to unshadow if it's not a PT, or if it's > l1.
- */
- if ( ( v->arch.paging.shadow.pagetable_dying
- || ( !d->arch.paging.shadow.pagetable_dying_op
- && v->arch.paging.shadow.last_emulated_mfn_for_unshadow ==
mfn_x(gmfn) ) )
- && sh_mfn_is_a_page_table(gmfn)
- && (!d->arch.paging.shadow.pagetable_dying_op ||
- !(mfn_to_page(gmfn)->shadow_flags
- & (SHF_L2_32|SHF_L2_PAE|SHF_L2H_PAE|SHF_L4_64))) )
- {
- perfc_incr(shadow_early_unshadow);
- sh_remove_shadows(d, gmfn, 1, 0 /* Fast, can fail to unshadow */ );
- TRACE_SHADOW_PATH_FLAG(TRCE_SFLAG_EARLY_UNSHADOW);
- }
- v->arch.paging.shadow.last_emulated_mfn_for_unshadow = mfn_x(gmfn);
-#endif
-}
-
-/* Stop counting towards early unshadows, as we've seen a real page fault */
-static inline void reset_early_unshadow(struct vcpu *v)
-{
-#if SHADOW_OPTIMIZATIONS & SHOPT_EARLY_UNSHADOW
- v->arch.paging.shadow.last_emulated_mfn_for_unshadow = mfn_x(INVALID_MFN);
-#endif
-}
-
-
-
-/**************************************************************************/
/* Optimization: Prefetch multiple L1 entries. This is called after we have
* demand-faulted a shadow l1e in the fault handler, to see if it's
* worth fetching some more.
@@ -2941,7 +2895,7 @@ static int sh_page_fault(struct vcpu *v,
* a not-present fault (by flipping two bits). */
ASSERT(regs->error_code & PFEC_page_present);
regs->error_code ^= (PFEC_reserved_bit|PFEC_page_present);
- reset_early_unshadow(v);
+ sh_reset_early_unshadow(v);
perfc_incr(shadow_fault_fast_gnp);
SHADOW_PRINTK("fast path not-present\n");
trace_shadow_gen(TRC_SHADOW_FAST_PROPAGATE, va);
@@ -2957,7 +2911,7 @@ static int sh_page_fault(struct vcpu *v,
}
perfc_incr(shadow_fault_fast_mmio);
SHADOW_PRINTK("fast path mmio %#"PRIpaddr"\n", gpa);
- reset_early_unshadow(v);
+ sh_reset_early_unshadow(v);
trace_shadow_gen(TRC_SHADOW_FAST_MMIO, va);
return (handle_mmio_with_translation(va, gpa >> PAGE_SHIFT, access)
? EXCRET_fault_fixed : 0);
@@ -3069,7 +3023,7 @@ static int sh_page_fault(struct vcpu *v,
{
perfc_incr(shadow_fault_bail_real_fault);
SHADOW_PRINTK("not a shadow fault\n");
- reset_early_unshadow(v);
+ sh_reset_early_unshadow(v);
regs->error_code = gw.pfec & PFEC_arch_mask;
goto propagate;
}
@@ -3095,7 +3049,7 @@ static int sh_page_fault(struct vcpu *v,
perfc_incr(shadow_fault_bail_bad_gfn);
SHADOW_PRINTK("BAD gfn=%"SH_PRI_gfn" gmfn=%"PRI_mfn"\n",
gfn_x(gfn), mfn_x(gmfn));
- reset_early_unshadow(v);
+ sh_reset_early_unshadow(v);
put_gfn(d, gfn_x(gfn));
goto propagate;
}
@@ -3284,7 +3238,7 @@ static int sh_page_fault(struct vcpu *v,
perfc_incr(shadow_fault_fixed);
d->arch.paging.log_dirty.fault_count++;
- reset_early_unshadow(v);
+ sh_reset_early_unshadow(v);
trace_shadow_fixup(gw.l1e, va);
done:
@@ -3399,7 +3353,7 @@ static int sh_page_fault(struct vcpu *v,
SHADOW_PRINTK("emulate: eip=%#lx esp=%#lx\n", regs->rip, regs->rsp);
- emul_ops = shadow_init_emulation(&emul_ctxt, regs);
+ emul_ops = shadow_init_emulation(&emul_ctxt, regs, GUEST_PTE_SIZE);
r = x86_emulate(&emul_ctxt.ctxt, emul_ops);
@@ -3539,7 +3493,7 @@ static int sh_page_fault(struct vcpu *v,
sh_audit_gw(v, &gw);
SHADOW_PRINTK("mmio %#"PRIpaddr"\n", gpa);
shadow_audit_tables(v);
- reset_early_unshadow(v);
+ sh_reset_early_unshadow(v);
paging_unlock(d);
put_gfn(d, gfn_x(gfn));
trace_shadow_gen(TRC_SHADOW_MMIO, va);
@@ -3550,7 +3504,7 @@ static int sh_page_fault(struct vcpu *v,
sh_audit_gw(v, &gw);
SHADOW_PRINTK("not a shadow fault\n");
shadow_audit_tables(v);
- reset_early_unshadow(v);
+ sh_reset_early_unshadow(v);
paging_unlock(d);
put_gfn(d, gfn_x(gfn));
@@ -4659,29 +4613,6 @@ static void sh_pagetable_dying(struct vc
/**************************************************************************/
/* Handling guest writes to pagetables. */
-/* Tidy up after the emulated write: mark pages dirty, verify the new
- * contents, and undo the mapping */
-static void emulate_unmap_dest(struct vcpu *v,
- void *addr,
- u32 bytes,
- struct sh_emulate_ctxt *sh_ctxt)
-{
- ASSERT(mfn_valid(sh_ctxt->mfn[0]));
-
- /* If we are writing lots of PTE-aligned zeros, might want to unshadow */
- if ( likely(bytes >= 4) && (*(u32 *)addr == 0) )
- {
- if ( ((unsigned long) addr & ((sizeof (guest_intpte_t)) - 1)) == 0 )
- check_for_early_unshadow(v, sh_ctxt->mfn[0]);
- /* Don't reset the heuristic if we're writing zeros at non-aligned
- * addresses, otherwise it doesn't catch REP MOVSD on PAE guests */
- }
- else
- reset_early_unshadow(v);
-
- sh_emulate_unmap_dest(v, addr, bytes, sh_ctxt);
-}
-
static int
sh_x86_emulate_write(struct vcpu *v, unsigned long vaddr, void *src,
u32 bytes, struct sh_emulate_ctxt *sh_ctxt)
@@ -4715,7 +4646,7 @@ sh_x86_emulate_write(struct vcpu *v, uns
#endif
}
- emulate_unmap_dest(v, addr, bytes, sh_ctxt);
+ sh_emulate_unmap_dest(v, addr, bytes, sh_ctxt);
shadow_audit_tables(v);
paging_unlock(v->domain);
return X86EMUL_OKAY;
@@ -4760,7 +4691,7 @@ sh_x86_emulate_cmpxchg(struct vcpu *v, u
" wanted %#lx now %#lx bytes %u\n",
vaddr, prev, old, new, *(unsigned long *)addr, bytes);
- emulate_unmap_dest(v, addr, bytes, sh_ctxt);
+ sh_emulate_unmap_dest(v, addr, bytes, sh_ctxt);
shadow_audit_tables(v);
paging_unlock(v->domain);
return rv;
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -721,6 +721,8 @@ struct sh_emulate_ctxt {
uint8_t insn_buf_bytes;
unsigned long insn_buf_eip;
+ unsigned int pte_size;
+
/* Cache of segment registers already gathered for this emulation. */
unsigned int valid_seg_regs;
struct segment_register seg_reg[6];
@@ -736,10 +738,19 @@ struct sh_emulate_ctxt {
};
const struct x86_emulate_ops *shadow_init_emulation(
- struct sh_emulate_ctxt *sh_ctxt, struct cpu_user_regs *regs);
+ struct sh_emulate_ctxt *sh_ctxt, struct cpu_user_regs *regs,
+ unsigned int pte_size);
void shadow_continue_emulation(
struct sh_emulate_ctxt *sh_ctxt, struct cpu_user_regs *regs);
+/* Stop counting towards early unshadows, as we've seen a real page fault */
+static inline void sh_reset_early_unshadow(struct vcpu *v)
+{
+#if SHADOW_OPTIMIZATIONS & SHOPT_EARLY_UNSHADOW
+ v->arch.paging.shadow.last_emulated_mfn_for_unshadow = mfn_x(INVALID_MFN);
+#endif
+}
+
#if (SHADOW_OPTIMIZATIONS & SHOPT_VIRTUAL_TLB)
/**************************************************************************/
/* Virtual TLB entries
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