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 <[email protected]> Signed-off-by: Bandan Das <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
