* [PATCH v1 0/2] KVM: arm64: Additional documentation of the FP code
@ 2022-01-24 15:57 ` Mark Brown
0 siblings, 0 replies; 8+ messages in thread
From: Mark Brown @ 2022-01-24 15:57 UTC (permalink / raw)
To: Marc Zyngier
Cc: James Morse, Alexandru Elisei, Suzuki K Poulose,
linux-arm-kernel, kvmarm, Mark Brown
These couple of patches add a few more comments to the floating point
code which will hopefully help the next person who comes along and tries
to figure out what is going on.
Mark Brown (2):
KVM: arm64: Add comments for context flush and sync callbacks
KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
arch/arm64/kvm/fpsimd.c | 14 ++++++++++----
arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++++
2 files changed, 14 insertions(+), 4 deletions(-)
base-commit: e783362eb54cd99b2cac8b3a9aeac942e6f6ac07
--
2.30.2
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^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH v1 1/2] KVM: arm64: Add comments for context flush and sync callbacks
2022-01-24 15:57 ` Mark Brown
@ 2022-01-24 15:57 ` Mark Brown
-1 siblings, 0 replies; 8+ messages in thread
From: Mark Brown @ 2022-01-24 15:57 UTC (permalink / raw)
To: Marc Zyngier; +Cc: Mark Brown, kvmarm, linux-arm-kernel
Add a little bit of information on where _ctxflush_fp() and _ctxsync_fp()
are called to help people unfamiliar with the code get up to speed.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/kvm/fpsimd.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 2f48fd362a8c..397fdac75cb1 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -84,6 +84,11 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
}
+/*
+ * Called just before entering the guest once we are no longer
+ * preemptable. Syncs the host's TIF_FOREIGN_FPSTATE with the KVM
+ * mirror of the flag used by the hypervisor.
+ */
void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
{
if (test_thread_flag(TIF_FOREIGN_FPSTATE))
@@ -93,10 +98,11 @@ void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
}
/*
- * If the guest FPSIMD state was loaded, update the host's context
- * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
- * so that they will be written back if the kernel clobbers them due to
- * kernel-mode NEON before re-entry into the guest.
+ * Called just after exiting the guest. If the guest FPSIMD state
+ * was loaded, update the host's context tracking data mark the CPU
+ * FPSIMD regs as dirty and belonging to vcpu so that they will be
+ * written back if the kernel clobbers them due to kernel-mode NEON
+ * before re-entry into the guest.
*/
void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
{
--
2.30.2
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^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH v1 1/2] KVM: arm64: Add comments for context flush and sync callbacks
@ 2022-01-24 15:57 ` Mark Brown
0 siblings, 0 replies; 8+ messages in thread
From: Mark Brown @ 2022-01-24 15:57 UTC (permalink / raw)
To: Marc Zyngier
Cc: James Morse, Alexandru Elisei, Suzuki K Poulose,
linux-arm-kernel, kvmarm, Mark Brown
Add a little bit of information on where _ctxflush_fp() and _ctxsync_fp()
are called to help people unfamiliar with the code get up to speed.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/kvm/fpsimd.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 2f48fd362a8c..397fdac75cb1 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -84,6 +84,11 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
}
+/*
+ * Called just before entering the guest once we are no longer
+ * preemptable. Syncs the host's TIF_FOREIGN_FPSTATE with the KVM
+ * mirror of the flag used by the hypervisor.
+ */
void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
{
if (test_thread_flag(TIF_FOREIGN_FPSTATE))
@@ -93,10 +98,11 @@ void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
}
/*
- * If the guest FPSIMD state was loaded, update the host's context
- * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
- * so that they will be written back if the kernel clobbers them due to
- * kernel-mode NEON before re-entry into the guest.
+ * Called just after exiting the guest. If the guest FPSIMD state
+ * was loaded, update the host's context tracking data mark the CPU
+ * FPSIMD regs as dirty and belonging to vcpu so that they will be
+ * written back if the kernel clobbers them due to kernel-mode NEON
+ * before re-entry into the guest.
*/
void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
{
--
2.30.2
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^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v1 2/2] KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
2022-01-24 15:57 ` Mark Brown
@ 2022-01-24 15:57 ` Mark Brown
-1 siblings, 0 replies; 8+ messages in thread
From: Mark Brown @ 2022-01-24 15:57 UTC (permalink / raw)
To: Marc Zyngier; +Cc: Mark Brown, kvmarm, linux-arm-kernel
The handling for FPSIMD/SVE traps is multi stage and involves some trap
manipulation which isn't quite so immediately obvious as might be desired
so add a few more comments.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 58e14f8ead23..1995808d8766 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -173,6 +173,8 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
return false;
/* Valid trap. Switch the context: */
+
+ /* First disable enough traps to allow us to update the registers */
if (has_vhe()) {
reg = CPACR_EL1_FPEN;
if (sve_guest)
@@ -188,11 +190,13 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
}
isb();
+ /* Write out the host state if it's in the registers */
if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
}
+ /* Restore the guest state */
if (sve_guest)
__hyp_sve_restore_guest(vcpu);
else
--
2.30.2
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^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH v1 2/2] KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
@ 2022-01-24 15:57 ` Mark Brown
0 siblings, 0 replies; 8+ messages in thread
From: Mark Brown @ 2022-01-24 15:57 UTC (permalink / raw)
To: Marc Zyngier
Cc: James Morse, Alexandru Elisei, Suzuki K Poulose,
linux-arm-kernel, kvmarm, Mark Brown
The handling for FPSIMD/SVE traps is multi stage and involves some trap
manipulation which isn't quite so immediately obvious as might be desired
so add a few more comments.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 58e14f8ead23..1995808d8766 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -173,6 +173,8 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
return false;
/* Valid trap. Switch the context: */
+
+ /* First disable enough traps to allow us to update the registers */
if (has_vhe()) {
reg = CPACR_EL1_FPEN;
if (sve_guest)
@@ -188,11 +190,13 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
}
isb();
+ /* Write out the host state if it's in the registers */
if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
}
+ /* Restore the guest state */
if (sve_guest)
__hyp_sve_restore_guest(vcpu);
else
--
2.30.2
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^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v1 0/2] KVM: arm64: Additional documentation of the FP code
2022-01-24 15:57 ` Mark Brown
@ 2022-02-08 17:37 ` Marc Zyngier
-1 siblings, 0 replies; 8+ messages in thread
From: Marc Zyngier @ 2022-02-08 17:37 UTC (permalink / raw)
To: Mark Brown; +Cc: kvmarm, linux-arm-kernel
On Mon, 24 Jan 2022 15:57:18 +0000, Mark Brown wrote:
> These couple of patches add a few more comments to the floating point
> code which will hopefully help the next person who comes along and tries
> to figure out what is going on.
>
> Mark Brown (2):
> KVM: arm64: Add comments for context flush and sync callbacks
> KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
>
> [...]
Applied to next, thanks!
[1/2] KVM: arm64: Add comments for context flush and sync callbacks
commit: 23afc82539cfcce105bf18c5c835c75e463ca349
[2/2] KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
commit: 01a244decc760b1ae2caa045647d79ff431bf37b
Cheers,
M.
--
Without deviation from the norm, progress is not possible.
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^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH v1 0/2] KVM: arm64: Additional documentation of the FP code
@ 2022-02-08 17:37 ` Marc Zyngier
0 siblings, 0 replies; 8+ messages in thread
From: Marc Zyngier @ 2022-02-08 17:37 UTC (permalink / raw)
To: Mark Brown; +Cc: kvmarm, linux-arm-kernel
On Mon, 24 Jan 2022 15:57:18 +0000, Mark Brown wrote:
> These couple of patches add a few more comments to the floating point
> code which will hopefully help the next person who comes along and tries
> to figure out what is going on.
>
> Mark Brown (2):
> KVM: arm64: Add comments for context flush and sync callbacks
> KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
>
> [...]
Applied to next, thanks!
[1/2] KVM: arm64: Add comments for context flush and sync callbacks
commit: 23afc82539cfcce105bf18c5c835c75e463ca349
[2/2] KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
commit: 01a244decc760b1ae2caa045647d79ff431bf37b
Cheers,
M.
--
Without deviation from the norm, progress is not possible.
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^ permalink raw reply [flat|nested] 8+ messages in thread