Re: [PATCH v2 11/17] kvm: arm64: Configure VTCR per VM

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On 03/05/18 15:39, James Morse wrote:
Hi Suzuki,

On 27/03/18 14:15, Suzuki K Poulose wrote:
We set VTCR_EL2 very early during the stage2 init and don't
touch it ever. This is fine as we had a fixed IPA size. This
patch changes the behavior to set the VTCR for a given VM,
depending on its stage2 table. The common configuration for
VTCR is still performed during the early init as we have to
retain the hardware access flag update bits (VTCR_EL2_HA)
per CPU (as they are only set for the CPUs which are capabile).
The bits defining the number of levels in the page table (SL0)
and and the size of the Input address to the translation (T0SZ)
are programmed for each VM upon entry to the guest.


diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 596f8e4..9f3c8b8 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -392,10 +392,12 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
static inline void __cpu_init_stage2(void)
  {
-	u32 parange = kvm_call_hyp(__init_stage2_translation);
+	u32 ps;
- WARN_ONCE(parange < 40,
-		  "PARange is %d bits, unsupported configuration!", parange);
+	kvm_call_hyp(__init_stage2_translation);
+	ps = id_aa64mmfr0_parange_to_phys_shift(read_sysreg(id_aa64mmfr0_el1));

Doesn't id_aa64mmfr0_parange_to_phys_shift() expect you do to the mask and shift
for it? This will always hit the default case.

Good catch ! The error case was not hit on the system I tested, as it was
indeed having 48bit PA. I should have done more testing with Juno where it
is 40bit PA (which doesn't really allow different phys-shift ranges).

I will change the helper to extract the parange and the convert it.
Also, rename it to :

id_aa64mmfr0_phys_shift()

Cheers
Suzuki



+	WARN_ONCE(ps < 40,
+		  "PARange is %d bits, unsupported configuration!", ps);
  }



Thanks,

James





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