On 04-01-2022 03:09 pm, Marc Zyngier wrote:
On Tue, 04 Jan 2022 08:53:42 +0000,
Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx> wrote:
On 30-11-2021 01:31 am, Marc Zyngier wrote:
From: Jintack Lim <jintack.lim@xxxxxxxxxx>
We enable nested virtualization by setting the HCR NV and NV1 bit.
When the virtual E2H bit is set, we can support EL2 register accesses
via EL1 registers from the virtual EL2 by doing trap-and-emulate. A
better alternative, however, is to allow the virtual EL2 to access EL2
register states without trap. This can be easily achieved by not traping
EL1 registers since those registers already have EL2 register states.
Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_arm.h | 1 +
arch/arm64/kvm/hyp/vhe/switch.c | 38 +++++++++++++++++++++++++++++---
2 files changed, 36 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 68af5509e4b0..b8a0d410035b 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -87,6 +87,7 @@
HCR_BSU_IS | HCR_FB | HCR_TACR | \
HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW | HCR_TLOR | \
HCR_FMO | HCR_IMO | HCR_PTW )
+#define HCR_GUEST_NV_FILTER_FLAGS (HCR_ATA | HCR_API | HCR_APK | HCR_RW)
#define HCR_VIRT_EXCP_MASK (HCR_VSE | HCR_VI | HCR_VF)
#define HCR_HOST_NVHE_FLAGS (HCR_RW | HCR_API | HCR_APK | HCR_ATA)
#define HCR_HOST_NVHE_PROTECTED_FLAGS (HCR_HOST_NVHE_FLAGS | HCR_TSC)
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 57f43e607819..da80c969e623 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -36,9 +36,41 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
u64 hcr = vcpu->arch.hcr_el2;
u64 val;
- /* Trap VM sysreg accesses if an EL2 guest is not using
VHE. */
- if (vcpu_mode_el2(vcpu) && !vcpu_el2_e2h_is_set(vcpu))
- hcr |= HCR_TVM | HCR_TRVM;
+ if (is_hyp_ctxt(vcpu)) {
+ hcr |= HCR_NV;
+
+ if (!vcpu_el2_e2h_is_set(vcpu)) {
+ /*
+ * For a guest hypervisor on v8.0, trap and emulate
+ * the EL1 virtual memory control register accesses.
+ */
+ hcr |= HCR_TVM | HCR_TRVM | HCR_NV1;
+ } else {
+ /*
+ * For a guest hypervisor on v8.1 (VHE), allow to
+ * access the EL1 virtual memory control registers
+ * natively. These accesses are to access EL2 register
+ * states.
+ * Note that we still need to respect the virtual
+ * HCR_EL2 state.
+ */
+ u64 vhcr_el2 = __vcpu_sys_reg(vcpu, HCR_EL2);
+
+ vhcr_el2 &= ~HCR_GUEST_NV_FILTER_FLAGS;
Why HCR_RW is cleared here, May I know please?
Good question. That's clearly a leftover from an early rework. It
really doesn't matter, as we are merging the guest's configuration
into the host's, and the host already has HCR_EL2.RW set.
Thanks, I too felt the same.
x>
What HCR_GUEST_NV_FILTER_FLAGS should contain is only the bits we
don't want to deal with at this stage of the NV support. I'll fix that
for the next round.
sure, thanks.
Thanks,
M.
Thanks,
Ganapat
