[PATCH 0/2] __do_hyp_init fix and tweak

[PATCH 0/2] __do_hyp_init fix and tweak

[Andrew Scull]

These apply on 5.11-rc4. The second is a fix for a clobbered register,
the first is more cosmetic.

Thanks, David, for helping with build and boot tests after my logistical
issues.

Andrew Scull (2):
  KVM: arm64: Simplify __kvm_hyp_init HVC detection
  KVM: arm64: Don't clobber x4 in __do_hyp_init

 arch/arm64/kvm/hyp/nvhe/hyp-init.S | 35 +++++++++++++-----------------
 1 file changed, 15 insertions(+), 20 deletions(-)

-- 
2.30.0.280.ga3ce27912f-goog

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH 1/2] KVM: arm64: Simplify __kvm_hyp_init HVC detection

[Andrew Scull]

The arguments for __do_hyp_init are now passed with a pointer to a
struct which means there are scratch registers available for use. Thanks
to this, we no longer need to use clever, but hard to read, tricks that
avoid the need for scratch registers when checking for the
__kvm_hyp_init HVC.

Tested-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Andrew Scull <ascull@google.com>
---
 arch/arm64/kvm/hyp/nvhe/hyp-init.S | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
index 31b060a44045..b3915ccb23b0 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
@@ -55,17 +55,10 @@ __do_hyp_init:
 	cmp	x0, #HVC_STUB_HCALL_NR
 	b.lo	__kvm_handle_stub_hvc
 
-	// We only actively check bits [24:31], and everything
-	// else has to be zero, which we check at build time.
-#if (KVM_HOST_SMCCC_FUNC(__kvm_hyp_init) & 0xFFFFFFFF00FFFFFF)
-#error Unexpected __KVM_HOST_SMCCC_FUNC___kvm_hyp_init value
-#endif
-
-	ror	x0, x0, #24
-	eor	x0, x0, #((KVM_HOST_SMCCC_FUNC(__kvm_hyp_init) >> 24) & 0xF)
-	ror	x0, x0, #4
-	eor	x0, x0, #((KVM_HOST_SMCCC_FUNC(__kvm_hyp_init) >> 28) & 0xF)
-	cbz	x0, 1f
+	mov	x3, #KVM_HOST_SMCCC_FUNC(__kvm_hyp_init)
+	cmp	x0, x3
+	b.eq	1f
+
 	mov	x0, #SMCCC_RET_NOT_SUPPORTED
 	eret
 
-- 
2.30.0.280.ga3ce27912f-goog

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

[PATCH 2/2] KVM: arm64: Don't clobber x4 in __do_hyp_init

[Andrew Scull]

arm_smccc_1_1_hvc() only adds write contraints for x0-3 in the inline
assembly for the HVC instruction so make sure those are the only
registers that change when __do_hyp_init is called.

Tested-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Andrew Scull <ascull@google.com>
---
 arch/arm64/kvm/hyp/nvhe/hyp-init.S | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
index b3915ccb23b0..3df583ad12af 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
@@ -47,6 +47,8 @@ __invalid:
 	b	.
 
 	/*
+	 * Only uses x0..x3 so as to not clobber callee-saved SMCCC registers.
+	 *
 	 * x0: SMCCC function ID
 	 * x1: struct kvm_nvhe_init_params PA
 	 */
@@ -63,9 +65,9 @@ __do_hyp_init:
 	eret
 
 1:	mov	x0, x1
-	mov	x4, lr
-	bl	___kvm_hyp_init
-	mov	lr, x4
+	mov	x3, lr
+	bl	___kvm_hyp_init			// Clobbers x0..x2
+	mov	lr, x3
 
 	/* Hello, World! */
 	mov	x0, #SMCCC_RET_SUCCESS
@@ -75,8 +77,8 @@ SYM_CODE_END(__kvm_hyp_init)
 /*
  * Initialize the hypervisor in EL2.
  *
- * Only uses x0..x3 so as to not clobber callee-saved SMCCC registers
- * and leave x4 for the caller.
+ * Only uses x0..x2 so as to not clobber callee-saved SMCCC registers
+ * and leave x3 for the caller.
  *
  * x0: struct kvm_nvhe_init_params PA
  */
@@ -105,9 +107,9 @@ alternative_else_nop_endif
 	/*
 	 * Set the PS bits in TCR_EL2.
 	 */
-	ldr	x1, [x0, #NVHE_INIT_TCR_EL2]
-	tcr_compute_pa_size x1, #TCR_EL2_PS_SHIFT, x2, x3
-	msr	tcr_el2, x1
+	ldr	x0, [x0, #NVHE_INIT_TCR_EL2]
+	tcr_compute_pa_size x0, #TCR_EL2_PS_SHIFT, x1, x2
+	msr	tcr_el2, x0
 
 	isb
 
@@ -186,7 +188,7 @@ SYM_CODE_START_LOCAL(__kvm_hyp_init_cpu)
 
 	/* Enable MMU, set vectors and stack. */
 	mov	x0, x28
-	bl	___kvm_hyp_init			// Clobbers x0..x3
+	bl	___kvm_hyp_init			// Clobbers x0..x2
 
 	/* Leave idmap. */
 	mov	x0, x29
-- 
2.30.0.280.ga3ce27912f-goog

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Re: (subset) [PATCH 0/2] __do_hyp_init fix and tweak

[Marc Zyngier]

On Mon, 25 Jan 2021 14:54:13 +0000, Andrew Scull wrote:
> These apply on 5.11-rc4. The second is a fix for a clobbered register,
> the first is more cosmetic.
> 
> Thanks, David, for helping with build and boot tests after my logistical
> issues.
> 
> Andrew Scull (2):
>   KVM: arm64: Simplify __kvm_hyp_init HVC detection
>   KVM: arm64: Don't clobber x4 in __do_hyp_init
> 
> [...]

Applied to kvmarm-master/fixes, thanks!

[2/2] KVM: arm64: Don't clobber x4 in __do_hyp_init
      commit: e500b805c39daff2670494fff94909d7e3d094d9

Cheers,

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


_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

Re: (subset) [PATCH 0/2] __do_hyp_init fix and tweak

[Marc Zyngier]

On Mon, 25 Jan 2021 14:54:13 +0000, Andrew Scull wrote:
> These apply on 5.11-rc4. The second is a fix for a clobbered register,
> the first is more cosmetic.
> 
> Thanks, David, for helping with build and boot tests after my logistical
> issues.
> 
> Andrew Scull (2):
>   KVM: arm64: Simplify __kvm_hyp_init HVC detection
>   KVM: arm64: Don't clobber x4 in __do_hyp_init
> 
> [...]

Applied to kvm-arm64/misc-5.12, thanks!

[1/2] KVM: arm64: Simplify __kvm_hyp_init HVC detection
      commit: 87b26801f02ca9d7a110eb598dae8cd5d3bcace2

Cheers,

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


_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm