From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: bdas@redhat.com, gleb@kernel.org
Subject: [PATCH 11/25] KVM: emulate: activate memory access optimization
Date: Mon, 9 Jun 2014 14:58:59 +0200 [thread overview]
Message-ID: <1402318753-23362-12-git-send-email-pbonzini@redhat.com> (raw)
In-Reply-To: <1402318753-23362-1-git-send-email-pbonzini@redhat.com>
memory_prepare lets us replace segmented_read/segmented_write with direct
calls to __copy_from_user/__copy_to_user. For RMW instructions, we also
avoid double walking of the page tables.
This saves about 50 cycles (5%) on arithmetic with a memory source
operand, and up to 300 cycles (20%) on arithmetic with a memory
destination operand.
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/include/asm/kvm_emulate.h | 2 ++
arch/x86/kvm/emulate.c | 72 +++++++++++++++++++++++++++++++++++---
2 files changed, 69 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 1aa2adf0bb1a..f596976a3ab2 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -263,6 +263,8 @@ struct operand {
u64 mm_val;
void *data;
};
+ unsigned long hva;
+ void *opaque;
};
struct fetch_cache {
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 7e9dc2d6fd44..594cb560947c 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1260,6 +1260,29 @@ read_cached:
return X86EMUL_CONTINUE;
}
+static int read_from_user(struct x86_emulate_ctxt *ctxt,
+ unsigned long hva, void *dest, unsigned size)
+{
+ int rc;
+ struct read_cache *mc = &ctxt->mem_read;
+
+ if (mc->pos < mc->end)
+ goto read_cached;
+
+ WARN_ON((mc->end + size) >= sizeof(mc->data));
+
+ rc = __copy_from_user(mc->data + mc->end, (void __user *)hva, size);
+ if (rc < 0)
+ return X86EMUL_UNHANDLEABLE;
+
+ mc->end += size;
+
+read_cached:
+ memcpy(dest, mc->data + mc->pos, size);
+ mc->pos += size;
+ return X86EMUL_CONTINUE;
+}
+
static int segmented_read(struct x86_emulate_ctxt *ctxt,
struct segmented_address addr,
void *data,
@@ -1565,9 +1588,36 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
}
static int prepare_memory_operand(struct x86_emulate_ctxt *ctxt,
- struct operand *op)
+ struct operand *op,
+ bool write)
{
- return segmented_read(ctxt, op->addr.mem, &op->val, op->bytes);
+ int rc;
+ unsigned long gva;
+ unsigned int size = op->bytes;
+
+ rc = linearize(ctxt, op->addr.mem, size, write, &gva);
+ if (rc != X86EMUL_CONTINUE)
+ return rc;
+
+ rc = ctxt->ops->memory_prepare(ctxt, gva, size,
+ &ctxt->exception, true,
+ &op->opaque, &op->hva);
+ if (rc != X86EMUL_CONTINUE)
+ return rc;
+
+ if (likely(!kvm_is_error_hva(op->hva))) {
+ rc = read_from_user(ctxt, op->hva, &op->val, size);
+ if (!write)
+ ctxt->ops->memory_finish(ctxt, op->opaque, op->hva);
+
+ if (likely(rc == X86EMUL_CONTINUE))
+ return X86EMUL_CONTINUE;
+
+ /* Should not happen. */
+ op->hva = KVM_HVA_ERR_BAD;
+ }
+
+ return read_emulated(ctxt, gva, &op->val, size);
}
static int cmpxchg_memory_operand(struct x86_emulate_ctxt *ctxt,
@@ -1582,6 +1632,17 @@ static int cmpxchg_memory_operand(struct x86_emulate_ctxt *ctxt,
static int write_memory_operand(struct x86_emulate_ctxt *ctxt,
struct operand *op)
{
+ int rc;
+
+ if (likely(!kvm_is_error_hva(op->hva))) {
+ rc = __copy_to_user((void __user *)op->hva, &op->val,
+ op->bytes);
+ ctxt->ops->memory_finish(ctxt, op->opaque, op->hva);
+
+ if (likely(!rc))
+ return X86EMUL_CONTINUE;
+ }
+
return segmented_write(ctxt, op->addr.mem,
&op->val,
op->bytes);
@@ -4638,14 +4699,14 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
}
if ((ctxt->src.type == OP_MEM) && !(ctxt->d & NoAccess)) {
- rc = prepare_memory_operand(ctxt, &ctxt->src);
+ rc = prepare_memory_operand(ctxt, &ctxt->src, false);
if (rc != X86EMUL_CONTINUE)
goto done;
ctxt->src.orig_val64 = ctxt->src.val64;
}
if (ctxt->src2.type == OP_MEM) {
- rc = prepare_memory_operand(ctxt, &ctxt->src2);
+ rc = prepare_memory_operand(ctxt, &ctxt->src2, false);
if (rc != X86EMUL_CONTINUE)
goto done;
}
@@ -4656,7 +4717,8 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
if ((ctxt->dst.type == OP_MEM) && !(ctxt->d & Mov)) {
/* optimisation - avoid slow emulated read if Mov */
- rc = prepare_memory_operand(ctxt, &ctxt->dst);
+ rc = prepare_memory_operand(ctxt, &ctxt->dst,
+ !(ctxt->d & NoWrite));
if (rc != X86EMUL_CONTINUE)
goto done;
}
--
1.8.3.1
next prev parent reply other threads:[~2014-06-09 13:03 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-09 12:58 [PATCH 00/25] KVM: x86: Speed up emulation of invalid state Paolo Bonzini
2014-06-09 12:58 ` [PATCH 01/25] KVM: vmx: speed up emulation of invalid guest state Paolo Bonzini
2014-06-09 12:58 ` [PATCH 02/25] KVM: x86: return all bits from get_interrupt_shadow Paolo Bonzini
2014-06-09 12:58 ` [PATCH 03/25] KVM: x86: avoid useless set of KVM_REQ_EVENT after emulation Paolo Bonzini
2014-06-09 12:58 ` [PATCH 04/25] KVM: emulate: move around some checks Paolo Bonzini
2014-06-09 12:58 ` [PATCH 05/25] KVM: emulate: protect checks on ctxt->d by a common "if (unlikely())" Paolo Bonzini
2014-06-09 12:58 ` [PATCH 06/25] KVM: emulate: speed up emulated moves Paolo Bonzini
2014-06-09 12:58 ` [PATCH 07/25] KVM: emulate: simplify writeback Paolo Bonzini
2014-06-09 12:58 ` [PATCH 08/25] KVM: emulate: abstract handling of memory operands Paolo Bonzini
2014-06-09 12:58 ` [PATCH 09/25] KVM: export mark_page_dirty_in_slot Paolo Bonzini
2014-06-09 12:58 ` [PATCH 10/25] KVM: emulate: introduce memory_prepare callback to speed up memory access Paolo Bonzini
2014-06-09 12:58 ` Paolo Bonzini [this message]
2014-06-09 12:59 ` [PATCH 12/25] KVM: emulate: extend memory access optimization to stores Paolo Bonzini
2014-06-09 18:40 ` Bandan Das
2014-06-19 11:37 ` Paolo Bonzini
2014-06-09 12:59 ` [PATCH 13/25] KVM: emulate: move init_decode_cache to emulate.c Paolo Bonzini
2014-06-09 12:59 ` [PATCH 14/25] KVM: emulate: Remove ctxt->intercept and ctxt->check_perm checks Paolo Bonzini
2014-06-09 12:59 ` [PATCH 15/25] KVM: emulate: cleanup decode_modrm Paolo Bonzini
2014-06-09 12:59 ` [PATCH 16/25] KVM: emulate: clean up initializations in init_decode_cache Paolo Bonzini
2014-06-09 12:59 ` [PATCH 17/25] KVM: emulate: rework seg_override Paolo Bonzini
2014-06-09 12:59 ` [PATCH 18/25] KVM: emulate: do not initialize memopp Paolo Bonzini
2014-06-09 12:59 ` [PATCH 19/25] KVM: emulate: speed up do_insn_fetch Paolo Bonzini
2014-06-09 12:59 ` [PATCH 20/25] KVM: emulate: avoid repeated calls to do_insn_fetch_bytes Paolo Bonzini
2014-06-09 12:59 ` [PATCH 21/25] KVM: emulate: avoid per-byte copying in instruction fetches Paolo Bonzini
2014-06-09 12:59 ` [PATCH 22/25] KVM: emulate: put pointers in the fetch_cache Paolo Bonzini
2014-06-09 12:59 ` [PATCH 23/25] KVM: x86: use kvm_read_guest_page for emulator accesses Paolo Bonzini
2014-06-09 12:59 ` [PATCH 24/25] KVM: emulate: simplify BitOp handling Paolo Bonzini
2014-06-09 12:59 ` [PATCH 25/25] KVM: emulate: fix harmless typo in MMX decoding Paolo Bonzini
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