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authorDave Martin <Dave.Martin@arm.com>2019-04-11 19:09:59 +0300
committerMarc Zyngier <marc.zyngier@arm.com>2019-04-18 19:14:02 +0300
commit4bd774e57b29f5bbf296d1daf69cc761e1e75fa8 (patch)
tree2fc0db55efc5503e96174bf549c6c822b9269e8e /Documentation/virtual
parent55ffad3b636a32dae03752078f4a0846bfd3a151 (diff)
downloadlinux-4bd774e57b29f5bbf296d1daf69cc761e1e75fa8.tar.xz
KVM: arm64/sve: Simplify KVM_REG_ARM64_SVE_VLS array sizing
A complicated DIV_ROUND_UP() expression is currently written out explicitly in multiple places in order to specify the size of the bitmap exchanged with userspace to represent the value of the KVM_REG_ARM64_SVE_VLS pseudo-register. Userspace currently has no direct way to work this out either: for documentation purposes, the size is just quoted as 8 u64s. To make this more intuitive, this patch replaces these with a single define, which is also exported to userspace as KVM_ARM64_SVE_VLS_WORDS. Since the number of words in a bitmap is just the index of the last word used + 1, this patch expresses the bound that way instead. This should make it clearer what is being expressed. For userspace convenience, the minimum and maximum possible vector lengths relevant to the KVM ABI are exposed to UAPI as KVM_ARM64_SVE_VQ_MIN, KVM_ARM64_SVE_VQ_MAX. Since the only direct use for these at present is manipulation of KVM_REG_ARM64_SVE_VLS, no corresponding _VL_ macros are defined. They could be added later if a need arises. Since use of DIV_ROUND_UP() was the only reason for including <linux/kernel.h> in guest.c, this patch also removes that #include. Suggested-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Dave Martin <Dave.Martin@arm.com> Reviewed-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt10
1 files changed, 6 insertions, 4 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 68509dee23e8..03df379a02b0 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 */