Re: [PATCH 09/14] KVM: arm64/sve: Simplify KVM_REG_ARM64_SVE_VLS array sizing

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On Tue, Apr 16, 2019 at 04:28:31PM +0200, Andrew Jones wrote:
> On Tue, Apr 16, 2019 at 03:10:55PM +0100, Dave Martin wrote:

[...]

> > arch/arm64/include/uapi/asm/kvm.h:
> > 
> > #include <asm/sve_context.h> /* which we already have anyway */
> > 
> > #define KVM_ARM64_SVE_VQ_MAX __SVE_VQ_MAX
> > #define KVM_ARM64_SVE_VQ_MIN __SVE_VQ_MIN
> > 
> > /* Vector lengths pseudo-register: */
> > #define KVM_REG_ARM64_SVE_VLS		(KVM_REG_ARM64 | KVM_REG_ARM64_SVE | \
> > 					 KVM_REG_SIZE_U512 | 0xffff)
> > #define KVM_ARM64_SVE_VLS_WORDS	\
> > 	((KVM_ARM64_SVE_VQ_MAX - KVM_ARM64_SVE_VQ_MIN) / 64 + 1)
> > 
> > 
> > Then document as follows:
> > Documentation/virtual/kvm/api.txt:
> > 
> > __u64 vector_lengths[KVM_ARM64_SVE_VLS_WORDS];
> > 
> > if (vq >= KVM_ARM64_SVE_VQ_MIN && vq <= KVM_ARM64_SVE_VQ_MAX)
> >     (vector_lengths[(vq - KVM_ARM64_SVE_VQ_MIN) / 64] >>
> > 		((vq - KVM_ARM64_SVE_VQ_MIN) % 64)) & 1)
> > 	/* Vector length vq * 16 bytes supported */
> > else
> > 	/* Vector length vq * 16 bytes not supported */
> > 
> > 
> > Does that work for you?
> > 
> > Doing things this way avoids people having to include <asm/sigcontext.h>
> > (and the consequent clashes with glibc headers).
> >
> 
> I like that.

OK, are you happy with the following on top of this patch?

Cheers
---Dave

--8<--

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 68509de..03df379 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2171,13 +2171,15 @@ and KVM_ARM_VCPU_FINALIZE for more information about this procedure.
 KVM_REG_ARM64_SVE_VLS is a pseudo-register that allows the set of vector
 lengths supported by the vcpu to be discovered and configured by
 userspace.  When transferred to or from user memory via KVM_GET_ONE_REG
-or KVM_SET_ONE_REG, the value of this register is of type __u64[8], and
-encodes the set of vector lengths as follows:
+or KVM_SET_ONE_REG, the value of this register is of type
+__u64[KVM_ARM64_SVE_VLS_WORDS], and encodes the set of vector lengths as
+follows:
 
-__u64 vector_lengths[8];
+__u64 vector_lengths[KVM_ARM64_SVE_VLS_WORDS];
 
 if (vq >= SVE_VQ_MIN && vq <= SVE_VQ_MAX &&
-    ((vector_lengths[(vq - 1) / 64] >> ((vq - 1) % 64)) & 1))
+    ((vector_lengths[(vq - KVM_ARM64_SVE_VQ_MIN) / 64] >>
+		((vq - KVM_ARM64_SVE_VQ_MIN) % 64)) & 1))
 	/* Vector length vq * 16 bytes supported */
 else
 	/* Vector length vq * 16 bytes not supported */
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 2a04ef0..edd2db8 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -258,9 +258,14 @@ struct kvm_vcpu_events {
 	 KVM_REG_SIZE_U256 |						\
 	 ((i) & (KVM_ARM64_SVE_MAX_SLICES - 1)))
 
+#define KVM_ARM64_SVE_VQ_MIN __SVE_VQ_MIN
+#define KVM_ARM64_SVE_VQ_MAX __SVE_VQ_MAX
+
 /* Vector lengths pseudo-register: */
 #define KVM_REG_ARM64_SVE_VLS		(KVM_REG_ARM64 | KVM_REG_ARM64_SVE | \
 					 KVM_REG_SIZE_U512 | 0xffff)
+#define KVM_ARM64_SVE_VLS_WORDS	\
+	((KVM_ARM64_SVE_VQ_MAX - KVM_ARM64_SVE_VQ_MIN) / 64 + 1)
 
 /* Device Control API: ARM VGIC */
 #define KVM_DEV_ARM_VGIC_GRP_ADDR	0
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index f025a2f..5bb909c 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -208,10 +208,8 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 #define vq_word(vq) (((vq) - SVE_VQ_MIN) / 64)
 #define vq_mask(vq) ((u64)1 << ((vq) - SVE_VQ_MIN) % 64)
 
-#define SVE_VLS_WORDS (vq_word(SVE_VQ_MAX) + 1)
-
 static bool vq_present(
-	const u64 (*const vqs)[SVE_VLS_WORDS],
+	const u64 (*const vqs)[KVM_ARM64_SVE_VLS_WORDS],
 	unsigned int vq)
 {
 	return (*vqs)[vq_word(vq)] & vq_mask(vq);
@@ -220,7 +218,7 @@ static bool vq_present(
 static int get_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 {
 	unsigned int max_vq, vq;
-	u64 vqs[SVE_VLS_WORDS];
+	u64 vqs[KVM_ARM64_SVE_VLS_WORDS];
 
 	if (!vcpu_has_sve(vcpu))
 		return -ENOENT;
@@ -244,7 +242,7 @@ static int get_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 static int set_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 {
 	unsigned int max_vq, vq;
-	u64 vqs[SVE_VLS_WORDS];
+	u64 vqs[KVM_ARM64_SVE_VLS_WORDS];
 
 	if (!vcpu_has_sve(vcpu))
 		return -ENOENT;

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