[PATCH] arm64: kvm: Remove kern_hyp_va from get_vcpu_ptr

[PATCH] arm64: kvm: Remove kern_hyp_va from get_vcpu_ptr

[Andrew Scull]

get_vcpu_ptr is an assembly accessor for the percpu value
kvm_host_data->host_ctxt.__hyp_running_vcpu. kern_hyp_va only applies to
nVHE however __hyp_running_vcpu is always assigned a pointer that has
already had kern_hyp_va applied in __kvm_vcpu_run_nvhe.

kern_hyp_va is currently idempotent as it just masks and inserts the
tag, but this could change in future and the second application is
unnecessary.

Signed-off-by: Andrew Scull <ascull@google.com>
---
Built with ARM64_HARDEN_EL2_VECTORS=y and tested on qemu A72 with
kvm-unit-tests and booting a VM with kvmtool.
---
 arch/arm64/include/asm/kvm_asm.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 352aaebf4198..ac71d0939f2e 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -143,7 +143,6 @@ extern char __smccc_workaround_1_smc[__SMCCC_WORKAROUND_1_SMC_SZ];
 .macro get_vcpu_ptr vcpu, ctxt
 	get_host_ctxt \ctxt, \vcpu
 	ldr	\vcpu, [\ctxt, #HOST_CONTEXT_VCPU]
-	kern_hyp_va	\vcpu
 .endm
 
 #endif
-- 
2.27.0.290.gba653c62da-goog

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Re: [PATCH] arm64: kvm: Remove kern_hyp_va from get_vcpu_ptr

[James Morse]

Hi Andrew,

On 18/06/2020 10:36, Andrew Scull wrote:
> get_vcpu_ptr is an assembly accessor for the percpu value
> kvm_host_data->host_ctxt.__hyp_running_vcpu. kern_hyp_va only applies to
> nVHE however __hyp_running_vcpu is always assigned a pointer that has
> already had kern_hyp_va applied in __kvm_vcpu_run_nvhe.

So it is!


> kern_hyp_va is currently idempotent as it just masks and inserts the
> tag, but this could change in future and the second application is
> unnecessary.


Reviewed-by: James Morse <james.morse@arm.com>


Thanks,

James
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Re: [PATCH] arm64: kvm: Remove kern_hyp_va from get_vcpu_ptr

[Marc Zyngier]

On Thu, 18 Jun 2020 10:36:16 +0100, Andrew Scull wrote:
> get_vcpu_ptr is an assembly accessor for the percpu value
> kvm_host_data->host_ctxt.__hyp_running_vcpu. kern_hyp_va only applies to
> nVHE however __hyp_running_vcpu is always assigned a pointer that has
> already had kern_hyp_va applied in __kvm_vcpu_run_nvhe.
> 
> kern_hyp_va is currently idempotent as it just masks and inserts the
> tag, but this could change in future and the second application is
> unnecessary.

Applied, thanks!

[1/1] arm64: kvm: Remove kern_hyp_va from get_vcpu_ptr
      commit: 2da3ffa6e840b9f8fc65a71326c43b716992861d

Best regards,
-- 
Without deviation from the norm, progress is not possible.

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