On 08/05/18 15:56, Paolo Bonzini wrote:
> On 08/05/2018 07:16, Christian Borntraeger wrote:
>> On 05/08/2018 07:14 AM, Paul Mackerras wrote:
>>> On Mon, May 07, 2018 at 03:18:46PM -0700, Marc Orr wrote:
>>>> The kvm struct is (currently) tens of kilo-bytes, which turns out to be a
>>>> large amount of memory to allocate contiguously via kzalloc. Thus, this
>>>> patch changes the kzalloc to a vzalloc, so that the memory allocation is
>>>> less likely to fail in resource-constrained environments.
>>>
>>> This will break HV KVM on powerpc, which needs the KVM struct to be
>>> physically contiguous and in the linear mapping. We'll need to add
>>> #define __KVM_HAVE_ARCH_VM_ALLOC to arch/powerpc/include/asm/kvm_host.h
>>> and the kzalloc/kfree variant to arch/powerpc/kvm/powerpc.c much like
>>> you did on arm.
>>
>> In the end I also want kmalloc for s390 (since we do not need the vmalloc for
>> s390 as we are < 16kb).
>>
>> So Paolo,
>> can we turn things around and only use vmalloc for x86?
>>
>
> The other idea that the #define would pick kzalloc vs. vzalloc (instead
> of enabling a custom kvm_arch_alloc_vm) would be even better I think.
I'm not sure it is better, as it forces the architecture to make that
choice at compile time, while I'd like to be able to do it at runtime.
Something like this (untested):
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index c6a749568dd6..b6b1bdafd08e 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -315,4 +315,8 @@ static inline bool kvm_arm_harden_branch_predictor(void)
static inline void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu) {}
static inline void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu) {}
+#define __KVM_HAVE_ARCH_VM_ALLOC
+struct kvm *kvm_arch_alloc_vm(void);
+void kvm_arch_free_vm(struct kvm *kvm);
+
#endif /* __ARM_KVM_HOST_H__ */
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index ab46bc70add6..51a64ff6965e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -452,4 +452,8 @@ static inline bool kvm_arm_harden_branch_predictor(void)
void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu);
void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu);
+#define __KVM_HAVE_ARCH_VM_ALLOC
+struct kvm *kvm_arch_alloc_vm(void);
+void kvm_arch_free_vm(struct kvm *kvm);
+
#endif /* __ARM64_KVM_HOST_H__ */
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index dba629c5f8ac..21d74e215519 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -249,6 +249,21 @@ long kvm_arch_dev_ioctl(struct file *filp,
return -EINVAL;
}
+struct kvm *kvm_arch_alloc_vm(void)
+{
+ if (!has_vhe())
+ return kzalloc(sizeof(struct kvm), GFP_KERNEL);
+
+ return vzalloc(sizeof(struct kvm));
+}
+
+void kvm_arch_free_vm(struct kvm *kvm)
+{
+ if (!has_vhe())
+ kfree(kvm);
+ else
+ vfree(kvm);
+}
struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
{
Thanks,
M.
--
Jazz is not dead. It just smells funny...
