On every instruction fetch, kvm_read_guest_virt_helper
does the gva to gpa translation followed by searching for the
memslot. Store the gva hva mapping so that if there's a match
we can directly call __copy_from_user()
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_emulate.h | 7 ++++++-
arch/x86/kvm/x86.c | 33 +++++++++++++++++++++++----------
2 files changed, 29 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 085d688..20ccde4 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -323,10 +323,11 @@ struct x86_emulate_ctxt {
int (*execute)(struct x86_emulate_ctxt *ctxt);
int (*check_perm)(struct x86_emulate_ctxt *ctxt);
/*
- * The following five fields are cleared together,
+ * The following six fields are cleared together,
* the rest are initialized unconditionally in x86_decode_insn
* or elsewhere
*/
+ bool addr_cache_valid;
u8 rex_prefix;
u8 lock_prefix;
u8 rep_prefix;
@@ -348,6 +349,10 @@ struct x86_emulate_ctxt {
struct fetch_cache fetch;
struct read_cache io_read;
struct read_cache mem_read;
+ struct {
+ gfn_t gfn;
+ unsigned long uaddr;
+ } addr_cache;
};
/* Repeat String Operation Prefix */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cf69e3b..7afcfc7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4072,26 +4072,38 @@ static int kvm_read_guest_virt_helper(gva_t addr, void *val, unsigned int bytes,
unsigned toread = min(bytes, (unsigned)PAGE_SIZE - offset);
int ret;
unsigned long uaddr;
+ gfn_t gfn = addr >> PAGE_SHIFT;
- ret = ctxt->ops->memory_prepare(ctxt, addr, toread,
- exception, false,
- NULL, &uaddr);
- if (ret != X86EMUL_CONTINUE)
- return ret;
+ if (ctxt->addr_cache_valid &&
+ (ctxt->addr_cache.gfn == gfn))
+ uaddr = (ctxt->addr_cache.uaddr << PAGE_SHIFT) +
+ offset_in_page(addr);
+ else {
+ ret = ctxt->ops->memory_prepare(ctxt, addr, toread,
+ exception, false,
+ NULL, &uaddr);
+ if (ret != X86EMUL_CONTINUE)
+ return ret;
+
+ if (unlikely(kvm_is_error_hva(uaddr))) {
+ r = X86EMUL_PROPAGATE_FAULT;
+ return r;
+ }
- if (unlikely(kvm_is_error_hva(uaddr))) {
- r = X86EMUL_PROPAGATE_FAULT;
- return r;
+ /* Cache gfn and hva */
+ ctxt->addr_cache.gfn = addr >> PAGE_SHIFT;
+ ctxt->addr_cache.uaddr = uaddr >> PAGE_SHIFT;
+ ctxt->addr_cache_valid = true;
}
ret = __copy_from_user(data, (void __user *)uaddr, toread);
if (ret < 0) {
r = X86EMUL_IO_NEEDED;
+ /* Where else should we invalidate cache ? */
+ ctxt->ops->memory_finish(ctxt, NULL, uaddr);
return r;
}
- ctxt->ops->memory_finish(ctxt, NULL, uaddr);
-
bytes -= toread;
data += toread;
addr += toread;
@@ -4339,6 +4351,7 @@ static void emulator_memory_finish(struct x86_emulate_ctxt *ctxt,
struct kvm_memory_slot *memslot;
gfn_t gfn;
+ ctxt->addr_cache_valid = false;
if (!opaque)
return;
--
1.8.3.1
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