Re: [PATCH v3 05/41] KVM: arm64: Move HCR_INT_OVERRIDE to default HCR_EL2 guest flag

[Christoffer Dall]

On Fri, Feb 09, 2018 at 11:38:50AM +, Julien Grall wrote:
> Hi,
> 
> On 01/12/2018 12:07 PM, Christoffer Dall wrote:
> >From: Shih-Wei Li 
> >
> >We always set the IMO and FMO bits in the HCR_EL2 when running the
> >guest, regardless if we use the vgic or not.  By moving these flags to
> >HCR_GUEST_FLAGS we can avoid one of the extra save/restore operations of
> >HCR_EL2 in the world switch code, and we can also soon get rid of the
> >other one.
> >
> >This is safe, because even though the IMO and FMO bits control both
> >taking the interrupts to EL2 and remapping ICC_*_EL1 to ICV_*_EL1
> >executed at EL1, as long as we ensure that these bits are clear when
> >running the EL1 host, as defined in the HCR_HOST_[VHE_]FLAGS, we're OK.
> 
> NIT: I was a bit confused by the end of the sentence because HCR_HOST_FLAGS
> define does not seem to exist.
> 

True, that was nonsense.

I have reworded it slightly.

Thanks,
-Christoffer
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Re: [PATCH v3 05/41] KVM: arm64: Move HCR_INT_OVERRIDE to default HCR_EL2 guest flag

[Julien Grall]

Hi,

On 01/12/2018 12:07 PM, Christoffer Dall wrote:

From: Shih-Wei Li 

We always set the IMO and FMO bits in the HCR_EL2 when running the
guest, regardless if we use the vgic or not.  By moving these flags to
HCR_GUEST_FLAGS we can avoid one of the extra save/restore operations of
HCR_EL2 in the world switch code, and we can also soon get rid of the
other one.

This is safe, because even though the IMO and FMO bits control both
taking the interrupts to EL2 and remapping ICC_*_EL1 to ICV_*_EL1
executed at EL1, as long as we ensure that these bits are clear when
running the EL1 host, as defined in the HCR_HOST_[VHE_]FLAGS, we're OK.


NIT: I was a bit confused by the end of the sentence because 
HCR_HOST_FLAGS define does not seem to exist.




Reviewed-by: Marc Zyngier 
Signed-off-by: Shih-Wei Li 
Signed-off-by: Christoffer Dall 
---
  arch/arm64/include/asm/kvm_arm.h | 4 ++--
  arch/arm64/kvm/hyp/switch.c  | 3 ---
  2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 715d395ef45b..656deeb17bf2 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -79,9 +79,9 @@
   */
  #define HCR_GUEST_FLAGS (HCR_TSC | HCR_TSW | HCR_TWE | HCR_TWI | HCR_VM | \
 HCR_TVM | HCR_BSU_IS | HCR_FB | HCR_TAC | \
-HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW)
+HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW | \
+HCR_FMO | HCR_IMO)
  #define HCR_VIRT_EXCP_MASK (HCR_VSE | HCR_VI | HCR_VF)
-#define HCR_INT_OVERRIDE   (HCR_FMO | HCR_IMO)
  #define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H)
  
  /* TCR_EL2 Registers bits */

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 71700ecee308..f6189d08753e 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -167,8 +167,6 @@ static void __hyp_text __vgic_save_state(struct kvm_vcpu 
*vcpu)
__vgic_v3_save_state(vcpu);
else
__vgic_v2_save_state(vcpu);
-
-   write_sysreg(read_sysreg(hcr_el2) & ~HCR_INT_OVERRIDE, hcr_el2);
  }
  
  static void __hyp_text __vgic_restore_state(struct kvm_vcpu *vcpu)

@@ -176,7 +174,6 @@ static void __hyp_text __vgic_restore_state(struct kvm_vcpu 
*vcpu)
u64 val;
  
  	val = read_sysreg(hcr_el2);

-   val |=  HCR_INT_OVERRIDE;
val |= vcpu->arch.irq_lines;
write_sysreg(val, hcr_el2);
  



Cheers,

--
Julien Grall
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