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| author | Paolo Bonzini <pbonzini@redhat.com> | 2014-05-13 14:02:13 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2014-07-11 09:14:04 +0200 |
| commit | 44583cba9188b29b20ceeefe8ae23ad19e26d9a4 (patch) | |
| tree | 5c5566b5d4398cfccc3dc88194dcc6571ffbdebd /arch/x86/kvm/x86.c | |
| parent | 719d5a9b2487e0562f178f61e323c3dc18a8b200 (diff) | |
| download | lwn-44583cba9188b29b20ceeefe8ae23ad19e26d9a4.tar.gz lwn-44583cba9188b29b20ceeefe8ae23ad19e26d9a4.zip | |
KVM: x86: use kvm_read_guest_page for emulator accesses
Emulator accesses are always done a page at a time, either by the emulator
itself (for fetches) or because we need to query the MMU for address
translations. Speed up these accesses by using kvm_read_guest_page
and, in the case of fetches, by inlining kvm_read_guest_virt_helper and
dropping the loop around kvm_read_guest_page.
This final tweak saves 30-100 more clock cycles (4-10%), bringing the
count (as measured by kvm-unit-tests) down to 720-1100 clock cycles on
a Sandy Bridge Xeon host, compared to 2300-3200 before the whole series
and 925-1700 after the first two low-hanging fruit changes.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 905edf8557e7..f750b69ca443 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4085,7 +4085,8 @@ static int kvm_read_guest_virt_helper(gva_t addr, void *val, unsigned int bytes, if (gpa == UNMAPPED_GVA) return X86EMUL_PROPAGATE_FAULT; - ret = kvm_read_guest(vcpu->kvm, gpa, data, toread); + ret = kvm_read_guest_page(vcpu->kvm, gpa >> PAGE_SHIFT, data, + offset, toread); if (ret < 0) { r = X86EMUL_IO_NEEDED; goto out; @@ -4106,10 +4107,24 @@ static int kvm_fetch_guest_virt(struct x86_emulate_ctxt *ctxt, { struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0; + unsigned offset; + int ret; - return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, - access | PFERR_FETCH_MASK, - exception); + /* Inline kvm_read_guest_virt_helper for speed. */ + gpa_t gpa = vcpu->arch.walk_mmu->gva_to_gpa(vcpu, addr, access|PFERR_FETCH_MASK, + exception); + if (unlikely(gpa == UNMAPPED_GVA)) + return X86EMUL_PROPAGATE_FAULT; + + offset = addr & (PAGE_SIZE-1); + if (WARN_ON(offset + bytes > PAGE_SIZE)) + bytes = (unsigned)PAGE_SIZE - offset; + ret = kvm_read_guest_page(vcpu->kvm, gpa >> PAGE_SHIFT, val, + offset, bytes); + if (unlikely(ret < 0)) + return X86EMUL_IO_NEEDED; + + return X86EMUL_CONTINUE; } int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt, |