From: Brijesh Singh <brijesh.singh@amd.com>
To: <pbonzini@redhat.com>, <rkrcmar@redhat.com>, <joro@8bytes.org>,
<kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: <tglx@linutronix.de>, <mingo@redhat.com>, <hpa@zytor.com>,
<x86@kernel.org>, <Thomas.Lendacky@amd.com>,
Brijesh Singh <brijesh.singh@amd.com>
Subject: [PATCH] x86: kvm: Avoid guest page table walk when gpa_available is set
Date: Mon, 24 Apr 2017 11:52:26 -0400 [thread overview]
Message-ID: <1493049146-19261-1-git-send-email-brijesh.singh@amd.com> (raw)
On AMD hardware when a guest causes a NFP which requires emulation,
the vcpu->arch.gpa_available flag is set to indicate that cr2 contains
a valid GPA.
Currently, emulator_read_write_onepage() makes use of gpa_available flag
to avoid a guest page walk for a known MMIO regions. Lets not limit
the gpa_available optimization to just MMIO region. The patch extends
the check to avoid page walk whenever gpa_available flag is set.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/svm.c | 4 ++++
arch/x86/kvm/x86.c | 26 +++++++++++++++-----------
3 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 74ef58c..491326d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -677,6 +677,7 @@ struct kvm_vcpu_arch {
/* GPA available (AMD only) */
bool gpa_available;
+ gpa_t gpa_val;
};
struct kvm_lpage_info {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 5fba706..8827e4b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4159,6 +4159,10 @@ static int handle_exit(struct kvm_vcpu *vcpu)
vcpu->arch.gpa_available = (exit_code == SVM_EXIT_NPF);
+ /* On #NPF, exit_info_2 contain a valid GPA */
+ if (vcpu->arch.gpa_available)
+ vcpu->arch.gpa_val = svm->vmcb->control.exit_info_2;
+
if (!is_cr_intercept(svm, INTERCEPT_CR0_WRITE))
vcpu->arch.cr0 = svm->vmcb->save.cr0;
if (npt_enabled)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ccbd45e..18ec746 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4653,18 +4653,16 @@ static int emulator_read_write_onepage(unsigned long addr, void *val,
* occurred.
*/
if (vcpu->arch.gpa_available &&
- emulator_can_use_gpa(ctxt) &&
- vcpu_is_mmio_gpa(vcpu, addr, exception->address, write) &&
- (addr & ~PAGE_MASK) == (exception->address & ~PAGE_MASK)) {
+ emulator_can_use_gpa(ctxt) &&
+ (addr & ~PAGE_MASK) == (exception->address & ~PAGE_MASK)) {
gpa = exception->address;
- goto mmio;
+ ret = vcpu_is_mmio_gpa(vcpu, addr, gpa, write);
+ } else {
+ ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write);
+ if (ret < 0)
+ return X86EMUL_PROPAGATE_FAULT;
}
- ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write);
-
- if (ret < 0)
- return X86EMUL_PROPAGATE_FAULT;
-
/* For APIC access vmexit */
if (ret)
goto mmio;
@@ -5675,8 +5673,14 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
}
restart:
- /* Save the faulting GPA (cr2) in the address field */
- ctxt->exception.address = cr2;
+ /*
+ * Save the faulting GPA (cr2) in the address field
+ * NOTE: If gpa_available is set then gpa_val will contain a valid GPA
+ */
+ if (vcpu->arch.gpa_available)
+ ctxt->exception.address = vcpu->arch.gpa_val;
+ else
+ ctxt->exception.address = cr2;
r = x86_emulate_insn(ctxt);
--
1.9.1
next reply other threads:[~2017-04-24 15:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-24 15:52 Brijesh Singh [this message]
2017-04-24 16:16 ` [PATCH] x86: kvm: Avoid guest page table walk when gpa_available is set Brijesh Singh
2017-04-24 20:52 ` Radim Krčmář
2017-04-24 22:14 ` Brijesh Singh
2017-04-25 14:03 ` Radim Krčmář
2017-04-25 22:02 ` Brijesh Singh
2017-04-26 20:44 ` Radim Krčmář
2017-04-28 19:15 ` Brijesh Singh
2017-05-02 16:24 ` Paolo Bonzini
2017-05-02 21:44 ` Brijesh Singh
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