diff mbox series

[6/9] KVM: arm64: Provide a PV_TIME device to user space

Message ID 20190802145017.42543-7-steven.price@arm.com
State New, archived
Headers show
Series arm64: Stolen time support | expand

Commit Message

Steven Price Aug. 2, 2019, 2:50 p.m. UTC
Allow user space to inform the KVM host where in the physical memory
map the paravirtualized time structures should be located.

A device is created which provides the base address of an array of
Stolen Time (ST) structures, one for each VCPU. There must be (64 *
total number of VCPUs) bytes of memory available at this location.

The address is given in terms of the physical address visible to
the guest and must be 64 byte aligned. The memory should be marked as
reserved to the guest to stop it allocating it for other purposes.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_mmu.h  |   2 +
 arch/arm64/include/uapi/asm/kvm.h |   6 +
 arch/arm64/kvm/Makefile           |   1 +
 include/uapi/linux/kvm.h          |   2 +
 virt/kvm/arm/mmu.c                |  44 +++++++
 virt/kvm/arm/pvtime.c             | 190 ++++++++++++++++++++++++++++++
 6 files changed, 245 insertions(+)
 create mode 100644 virt/kvm/arm/pvtime.c

Comments

Marc Zyngier Aug. 3, 2019, 12:51 p.m. UTC | #1
On Fri,  2 Aug 2019 15:50:14 +0100
Steven Price <steven.price@arm.com> wrote:

> Allow user space to inform the KVM host where in the physical memory
> map the paravirtualized time structures should be located.
> 
> A device is created which provides the base address of an array of
> Stolen Time (ST) structures, one for each VCPU. There must be (64 *
> total number of VCPUs) bytes of memory available at this location.
> 
> The address is given in terms of the physical address visible to
> the guest and must be 64 byte aligned. The memory should be marked as
> reserved to the guest to stop it allocating it for other purposes.

Why? You seem to be allocating the memory from the kernel, so as far as
the guest is concerned, this isn't generally usable memory.

> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm64/include/asm/kvm_mmu.h  |   2 +
>  arch/arm64/include/uapi/asm/kvm.h |   6 +
>  arch/arm64/kvm/Makefile           |   1 +
>  include/uapi/linux/kvm.h          |   2 +
>  virt/kvm/arm/mmu.c                |  44 +++++++
>  virt/kvm/arm/pvtime.c             | 190 ++++++++++++++++++++++++++++++
>  6 files changed, 245 insertions(+)
>  create mode 100644 virt/kvm/arm/pvtime.c
> 
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index befe37d4bc0e..88c8a4b2836f 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -157,6 +157,8 @@ int kvm_alloc_stage2_pgd(struct kvm *kvm);
>  void kvm_free_stage2_pgd(struct kvm *kvm);
>  int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>  			  phys_addr_t pa, unsigned long size, bool writable);
> +int kvm_phys_addr_memremap(struct kvm *kvm, phys_addr_t guest_ipa,
> +			  phys_addr_t pa, unsigned long size, bool writable);
>  
>  int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
>  
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 9a507716ae2f..95516a4198ea 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -367,6 +367,12 @@ struct kvm_vcpu_events {
>  #define KVM_PSCI_RET_INVAL		PSCI_RET_INVALID_PARAMS
>  #define KVM_PSCI_RET_DENIED		PSCI_RET_DENIED
>  
> +/* Device Control API: PV_TIME */
> +#define KVM_DEV_ARM_PV_TIME_PADDR	0
> +#define  KVM_DEV_ARM_PV_TIME_ST		0
> +#define KVM_DEV_ARM_PV_TIME_STATE_SIZE	1
> +#define KVM_DEV_ARM_PV_TIME_STATE	2
> +
>  #endif
>  
>  #endif /* __ARM_KVM_H__ */
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 73dce4d47d47..5ffbdc39e780 100644
> --- a/arch/arm64/kvm/Makefile
> +++ b/arch/arm64/kvm/Makefile
> @@ -14,6 +14,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/e
>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.o
>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hypercalls.o
> +kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/pvtime.o
>  
>  kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
>  kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index a7c19540ce21..04bffafa0708 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1222,6 +1222,8 @@ enum kvm_device_type {
>  #define KVM_DEV_TYPE_ARM_VGIC_ITS	KVM_DEV_TYPE_ARM_VGIC_ITS
>  	KVM_DEV_TYPE_XIVE,
>  #define KVM_DEV_TYPE_XIVE		KVM_DEV_TYPE_XIVE
> +	KVM_DEV_TYPE_ARM_PV_TIME,
> +#define KVM_DEV_TYPE_ARM_PV_TIME	KVM_DEV_TYPE_ARM_PV_TIME
>  	KVM_DEV_TYPE_MAX,
>  };
>  
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index 38b4c910b6c3..be28a4aee451 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -1368,6 +1368,50 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>  	return ret;
>  }
>  
> +/**
> + * kvm_phys_addr_memremap - map a memory range to guest IPA
> + *
> + * @kvm:	The KVM pointer
> + * @guest_ipa:	The IPA at which to insert the mapping
> + * @pa:		The physical address of the memory
> + * @size:	The size of the mapping
> + */
> +int kvm_phys_addr_memremap(struct kvm *kvm, phys_addr_t guest_ipa,
> +			  phys_addr_t pa, unsigned long size, bool writable)
> +{
> +	phys_addr_t addr, end;
> +	int ret = 0;
> +	unsigned long pfn;
> +	struct kvm_mmu_memory_cache cache = { 0, };
> +
> +	end = (guest_ipa + size + PAGE_SIZE - 1) & PAGE_MASK;
> +	pfn = __phys_to_pfn(pa);
> +
> +	for (addr = guest_ipa; addr < end; addr += PAGE_SIZE) {
> +		pte_t pte = pfn_pte(pfn, PAGE_S2);
> +
> +		if (writable)
> +			pte = kvm_s2pte_mkwrite(pte);
> +
> +		ret = mmu_topup_memory_cache(&cache,
> +					     kvm_mmu_cache_min_pages(kvm),
> +					     KVM_NR_MEM_OBJS);
> +		if (ret)
> +			goto out;
> +		spin_lock(&kvm->mmu_lock);
> +		ret = stage2_set_pte(kvm, &cache, addr, &pte, 0);
> +		spin_unlock(&kvm->mmu_lock);
> +		if (ret)
> +			goto out;
> +
> +		pfn++;
> +	}
> +
> +out:
> +	mmu_free_memory_cache(&cache);
> +	return ret;
> +}

This is an exact copy of kvm_phys_addr_ioremap(), with only the memory
attributes changing. Surely we can have a shared implementation that
takes the memory attribute as a parameter.

> +
>  static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
>  {
>  	kvm_pfn_t pfn = *pfnp;
> diff --git a/virt/kvm/arm/pvtime.c b/virt/kvm/arm/pvtime.c
> new file mode 100644
> index 000000000000..9051bc07eae1
> --- /dev/null
> +++ b/virt/kvm/arm/pvtime.c
> @@ -0,0 +1,190 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2019 Arm Ltd.
> +
> +#include <linux/kvm_host.h>
> +#include <asm/kvm_mmu.h>
> +
> +/* We currently only support PV time on ARM64 */
> +#ifdef CONFIG_ARM64

And we're only compiling it on arm64, so why the #ifdef?

> +
> +#include <asm/pvclock-abi.h>
> +
> +static int max_stolen_size(void)
> +{
> +	int size = KVM_MAX_VCPUS * sizeof(struct pvclock_vcpu_stolen_time_info);

So we're always allocating enough memory for 512 CPUs? That's an
additional 32kB of contiguous memory...

> +
> +	return ALIGN(size, PAGE_SIZE);
> +}
> +
> +static int kvm_arm_pvtime_create(struct kvm_device *dev, u32 type)
> +{
> +	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
> +
> +	pvtime->st = alloc_pages_exact(max_stolen_size(),
> +				       GFP_KERNEL | __GFP_ZERO);
> +	if (!pvtime->st)
> +		return -ENOMEM;

Is there any chance we could use a vmalloc allocation instead? This
would lift the requirement on having physically contiguous memory.

> +
> +	return 0;
> +}
> +
> +static void kvm_arm_pvtime_destroy(struct kvm_device *dev)
> +{
> +	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
> +
> +	pvtime->st_base = GPA_INVALID;
> +	free_pages_exact(pvtime->st, max_stolen_size());
> +	kfree(dev);
> +}
> +
> +static int pvtime_map_pages(struct kvm *kvm, gpa_t guest_paddr,
> +			    void *kaddr, int size)
> +{
> +	return kvm_phys_addr_memremap(kvm, guest_paddr,
> +			virt_to_phys(kaddr),
> +			size, false);
> +}
> +
> +static int pvtime_save_state(struct kvm *kvm, u64 type, void __user *user)
> +{
> +	void *source;
> +	size_t size;
> +
> +	switch (type) {
> +	case KVM_DEV_ARM_PV_TIME_ST:
> +		source = kvm->arch.pvtime.st;
> +		size = sizeof(struct pvclock_vcpu_stolen_time_info) *
> +			atomic_read(&kvm->online_vcpus);
> +		break;
> +	default:
> +		return -ENXIO;
> +	}
> +
> +	if (copy_to_user(user, source, size))
> +		return -EFAULT;
> +	return 0;
> +}
> +
> +static int pvtime_restore_state(struct kvm *kvm, u64 type, void __user *user)
> +{
> +	void *dest;
> +	size_t size;
> +
> +	switch (type) {
> +	case KVM_DEV_ARM_PV_TIME_ST:
> +		dest = kvm->arch.pvtime.st;
> +		size = sizeof(struct pvclock_vcpu_stolen_time_info) *
> +			atomic_read(&kvm->online_vcpus);
> +		break;
> +	default:
> +		return -ENXIO;
> +	}
> +
> +	if (copy_from_user(dest, user, size))
> +		return -EFAULT;
> +
> +	return 0;
> +}
> +
> +static int kvm_arm_pvtime_set_attr(struct kvm_device *dev,
> +				   struct kvm_device_attr *attr)
> +{
> +	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
> +	u64 __user *user = (u64 __user *)attr->addr;
> +	u64 paddr;
> +	int ret;
> +
> +	switch (attr->group) {
> +	case KVM_DEV_ARM_PV_TIME_PADDR:
> +		if (get_user(paddr, user))
> +			return -EFAULT;
> +		if (paddr & 63)
> +			return -EINVAL;

You should check whether the device fits into the IPA space for this
guest, and whether it overlaps with anything else.

> +		switch (attr->attr) {
> +		case KVM_DEV_ARM_PV_TIME_ST:
> +			if (pvtime->st_base != GPA_INVALID)
> +				return -EEXIST;
> +			ret = pvtime_map_pages(dev->kvm, paddr, pvtime->st,
> +					max_stolen_size());

Consider moving the size directly into pvtime_map_pages(), and dropping
the pvtime->st parameter. All you need is kvm and paddr.

> +			if (ret)
> +				return ret;
> +			pvtime->st_base = paddr;
> +			return 0;
> +		}
> +		break;
> +	case KVM_DEV_ARM_PV_TIME_STATE_SIZE:
> +		return -EPERM;
> +	case KVM_DEV_ARM_PV_TIME_STATE:
> +		return pvtime_restore_state(dev->kvm, attr->attr, user);
> +	}
> +	return -ENXIO;
> +}
> +
> +static int kvm_arm_pvtime_get_attr(struct kvm_device *dev,
> +				   struct kvm_device_attr *attr)
> +{
> +	u64 __user *user = (u64 __user *)attr->addr;
> +	u32 size;
> +
> +	switch (attr->group) {
> +	case KVM_DEV_ARM_PV_TIME_PADDR:
> +		switch (attr->attr) {
> +		case KVM_DEV_ARM_PV_TIME_ST:
> +			if (put_user(dev->kvm->arch.pvtime.st_base, user))
> +				return -EFAULT;
> +			return 0;
> +		}
> +		break;
> +	case KVM_DEV_ARM_PV_TIME_STATE_SIZE:
> +		switch (attr->attr) {
> +		case KVM_DEV_ARM_PV_TIME_ST:
> +			size = sizeof(struct pvclock_vcpu_stolen_time_info);
> +			size *= atomic_read(&dev->kvm->online_vcpus);
> +			break;
> +		default:
> +			return -ENXIO;
> +		}
> +		if (put_user(size, user))
> +			return -EFAULT;
> +		return 0;
> +	case KVM_DEV_ARM_PV_TIME_STATE:
> +		return pvtime_save_state(dev->kvm, attr->attr, user);
> +	}
> +	return -ENXIO;
> +}
> +
> +static int kvm_arm_pvtime_has_attr(struct kvm_device *dev,
> +				   struct kvm_device_attr *attr)
> +{
> +	switch (attr->group) {
> +	case KVM_DEV_ARM_PV_TIME_PADDR:
> +	case KVM_DEV_ARM_PV_TIME_STATE_SIZE:
> +	case KVM_DEV_ARM_PV_TIME_STATE:
> +		switch (attr->attr) {
> +		case KVM_DEV_ARM_PV_TIME_ST:
> +			return 0;
> +		}
> +		break;
> +	}
> +	return -ENXIO;
> +}
> +
> +static const struct kvm_device_ops pvtime_ops = {
> +	"Arm PV time",
> +	.create = kvm_arm_pvtime_create,
> +	.destroy = kvm_arm_pvtime_destroy,
> +	.set_attr = kvm_arm_pvtime_set_attr,
> +	.get_attr = kvm_arm_pvtime_get_attr,
> +	.has_attr = kvm_arm_pvtime_has_attr
> +};
> +
> +static int __init kvm_pvtime_init(void)
> +{
> +	kvm_register_device_ops(&pvtime_ops, KVM_DEV_TYPE_ARM_PV_TIME);
> +
> +	return 0;
> +}
> +
> +late_initcall(kvm_pvtime_init);
> +
> +#endif

Thanks,

	M.
Marc Zyngier Aug. 3, 2019, 5:34 p.m. UTC | #2
On Sat, 3 Aug 2019 13:51:13 +0100
Marc Zyngier <maz@kernel.org> wrote:

[forgot that one]

> On Fri,  2 Aug 2019 15:50:14 +0100
> Steven Price <steven.price@arm.com> wrote:

[...]

> > +static int __init kvm_pvtime_init(void)
> > +{
> > +	kvm_register_device_ops(&pvtime_ops, KVM_DEV_TYPE_ARM_PV_TIME);
> > +
> > +	return 0;
> > +}
> > +
> > +late_initcall(kvm_pvtime_init);

Why is it an initcall? So far, the only initcall we've used is the one
that initializes KVM itself. Can't we just the device_ops just like we
do for the vgic?

	M.
Steven Price Aug. 5, 2019, 4:10 p.m. UTC | #3
On 03/08/2019 13:51, Marc Zyngier wrote:
> On Fri,  2 Aug 2019 15:50:14 +0100
> Steven Price <steven.price@arm.com> wrote:
> 
>> Allow user space to inform the KVM host where in the physical memory
>> map the paravirtualized time structures should be located.
>>
>> A device is created which provides the base address of an array of
>> Stolen Time (ST) structures, one for each VCPU. There must be (64 *
>> total number of VCPUs) bytes of memory available at this location.
>>
>> The address is given in terms of the physical address visible to
>> the guest and must be 64 byte aligned. The memory should be marked as
>> reserved to the guest to stop it allocating it for other purposes.
> 
> Why? You seem to be allocating the memory from the kernel, so as far as
> the guest is concerned, this isn't generally usable memory.

I obviously didn't word it very well - that's what I meant. The "memory"
that represents the stolen time structure shouldn't be shown to the
guest as normal memory, but "reserved" for the purpose of stolen time.

To be honest it looks like I forgot to rewrite this commit message -
which 64 byte alignment is all that the guest can rely on (because each
vCPU has it's own structure), the actual array of structures needs to be
page aligned to ensure we can safely map it into the guest.

>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>  arch/arm64/include/asm/kvm_mmu.h  |   2 +
>>  arch/arm64/include/uapi/asm/kvm.h |   6 +
>>  arch/arm64/kvm/Makefile           |   1 +
>>  include/uapi/linux/kvm.h          |   2 +
>>  virt/kvm/arm/mmu.c                |  44 +++++++
>>  virt/kvm/arm/pvtime.c             | 190 ++++++++++++++++++++++++++++++
>>  6 files changed, 245 insertions(+)
>>  create mode 100644 virt/kvm/arm/pvtime.c
>>
>> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
>> index befe37d4bc0e..88c8a4b2836f 100644
>> --- a/arch/arm64/include/asm/kvm_mmu.h
>> +++ b/arch/arm64/include/asm/kvm_mmu.h
>> @@ -157,6 +157,8 @@ int kvm_alloc_stage2_pgd(struct kvm *kvm);
>>  void kvm_free_stage2_pgd(struct kvm *kvm);
>>  int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>>  			  phys_addr_t pa, unsigned long size, bool writable);
>> +int kvm_phys_addr_memremap(struct kvm *kvm, phys_addr_t guest_ipa,
>> +			  phys_addr_t pa, unsigned long size, bool writable);
>>  
>>  int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
>>  
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index 9a507716ae2f..95516a4198ea 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -367,6 +367,12 @@ struct kvm_vcpu_events {
>>  #define KVM_PSCI_RET_INVAL		PSCI_RET_INVALID_PARAMS
>>  #define KVM_PSCI_RET_DENIED		PSCI_RET_DENIED
>>  
>> +/* Device Control API: PV_TIME */
>> +#define KVM_DEV_ARM_PV_TIME_PADDR	0
>> +#define  KVM_DEV_ARM_PV_TIME_ST		0
>> +#define KVM_DEV_ARM_PV_TIME_STATE_SIZE	1
>> +#define KVM_DEV_ARM_PV_TIME_STATE	2
>> +
>>  #endif
>>  
>>  #endif /* __ARM_KVM_H__ */
>> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
>> index 73dce4d47d47..5ffbdc39e780 100644
>> --- a/arch/arm64/kvm/Makefile
>> +++ b/arch/arm64/kvm/Makefile
>> @@ -14,6 +14,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/e
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hypercalls.o
>> +kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/pvtime.o
>>  
>>  kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index a7c19540ce21..04bffafa0708 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -1222,6 +1222,8 @@ enum kvm_device_type {
>>  #define KVM_DEV_TYPE_ARM_VGIC_ITS	KVM_DEV_TYPE_ARM_VGIC_ITS
>>  	KVM_DEV_TYPE_XIVE,
>>  #define KVM_DEV_TYPE_XIVE		KVM_DEV_TYPE_XIVE
>> +	KVM_DEV_TYPE_ARM_PV_TIME,
>> +#define KVM_DEV_TYPE_ARM_PV_TIME	KVM_DEV_TYPE_ARM_PV_TIME
>>  	KVM_DEV_TYPE_MAX,
>>  };
>>  
>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
>> index 38b4c910b6c3..be28a4aee451 100644
>> --- a/virt/kvm/arm/mmu.c
>> +++ b/virt/kvm/arm/mmu.c
>> @@ -1368,6 +1368,50 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>>  	return ret;
>>  }
>>  
>> +/**
>> + * kvm_phys_addr_memremap - map a memory range to guest IPA
>> + *
>> + * @kvm:	The KVM pointer
>> + * @guest_ipa:	The IPA at which to insert the mapping
>> + * @pa:		The physical address of the memory
>> + * @size:	The size of the mapping
>> + */
>> +int kvm_phys_addr_memremap(struct kvm *kvm, phys_addr_t guest_ipa,
>> +			  phys_addr_t pa, unsigned long size, bool writable)
>> +{
>> +	phys_addr_t addr, end;
>> +	int ret = 0;
>> +	unsigned long pfn;
>> +	struct kvm_mmu_memory_cache cache = { 0, };
>> +
>> +	end = (guest_ipa + size + PAGE_SIZE - 1) & PAGE_MASK;
>> +	pfn = __phys_to_pfn(pa);
>> +
>> +	for (addr = guest_ipa; addr < end; addr += PAGE_SIZE) {
>> +		pte_t pte = pfn_pte(pfn, PAGE_S2);
>> +
>> +		if (writable)
>> +			pte = kvm_s2pte_mkwrite(pte);
>> +
>> +		ret = mmu_topup_memory_cache(&cache,
>> +					     kvm_mmu_cache_min_pages(kvm),
>> +					     KVM_NR_MEM_OBJS);
>> +		if (ret)
>> +			goto out;
>> +		spin_lock(&kvm->mmu_lock);
>> +		ret = stage2_set_pte(kvm, &cache, addr, &pte, 0);
>> +		spin_unlock(&kvm->mmu_lock);
>> +		if (ret)
>> +			goto out;
>> +
>> +		pfn++;
>> +	}
>> +
>> +out:
>> +	mmu_free_memory_cache(&cache);
>> +	return ret;
>> +}
> 
> This is an exact copy of kvm_phys_addr_ioremap(), with only the memory
> attributes changing. Surely we can have a shared implementation that
> takes the memory attribute as a parameter.

Good point - although due to below I'm going to need something which can
deal with non-contiguous memory...

>> +
>>  static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
>>  {
>>  	kvm_pfn_t pfn = *pfnp;
>> diff --git a/virt/kvm/arm/pvtime.c b/virt/kvm/arm/pvtime.c
>> new file mode 100644
>> index 000000000000..9051bc07eae1
>> --- /dev/null
>> +++ b/virt/kvm/arm/pvtime.c
>> @@ -0,0 +1,190 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +// Copyright (C) 2019 Arm Ltd.
>> +
>> +#include <linux/kvm_host.h>
>> +#include <asm/kvm_mmu.h>
>> +
>> +/* We currently only support PV time on ARM64 */
>> +#ifdef CONFIG_ARM64
> 
> And we're only compiling it on arm64, so why the #ifdef?

Another good point - will remove.

>> +
>> +#include <asm/pvclock-abi.h>
>> +
>> +static int max_stolen_size(void)
>> +{
>> +	int size = KVM_MAX_VCPUS * sizeof(struct pvclock_vcpu_stolen_time_info);
> 
> So we're always allocating enough memory for 512 CPUs? That's an
> additional 32kB of contiguous memory...
> 
>> +
>> +	return ALIGN(size, PAGE_SIZE);
>> +}
>> +
>> +static int kvm_arm_pvtime_create(struct kvm_device *dev, u32 type)
>> +{
>> +	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
>> +
>> +	pvtime->st = alloc_pages_exact(max_stolen_size(),
>> +				       GFP_KERNEL | __GFP_ZERO);
>> +	if (!pvtime->st)
>> +		return -ENOMEM;
> 
> Is there any chance we could use a vmalloc allocation instead? This
> would lift the requirement on having physically contiguous memory.

Yes I think it should be possible to use non-contiguous memory and vmalloc.

>> +
>> +	return 0;
>> +}
>> +
>> +static void kvm_arm_pvtime_destroy(struct kvm_device *dev)
>> +{
>> +	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
>> +
>> +	pvtime->st_base = GPA_INVALID;
>> +	free_pages_exact(pvtime->st, max_stolen_size());
>> +	kfree(dev);
>> +}
>> +
>> +static int pvtime_map_pages(struct kvm *kvm, gpa_t guest_paddr,
>> +			    void *kaddr, int size)
>> +{
>> +	return kvm_phys_addr_memremap(kvm, guest_paddr,
>> +			virt_to_phys(kaddr),
>> +			size, false);
>> +}
>> +
>> +static int pvtime_save_state(struct kvm *kvm, u64 type, void __user *user)
>> +{
>> +	void *source;
>> +	size_t size;
>> +
>> +	switch (type) {
>> +	case KVM_DEV_ARM_PV_TIME_ST:
>> +		source = kvm->arch.pvtime.st;
>> +		size = sizeof(struct pvclock_vcpu_stolen_time_info) *
>> +			atomic_read(&kvm->online_vcpus);
>> +		break;
>> +	default:
>> +		return -ENXIO;
>> +	}
>> +
>> +	if (copy_to_user(user, source, size))
>> +		return -EFAULT;
>> +	return 0;
>> +}
>> +
>> +static int pvtime_restore_state(struct kvm *kvm, u64 type, void __user *user)
>> +{
>> +	void *dest;
>> +	size_t size;
>> +
>> +	switch (type) {
>> +	case KVM_DEV_ARM_PV_TIME_ST:
>> +		dest = kvm->arch.pvtime.st;
>> +		size = sizeof(struct pvclock_vcpu_stolen_time_info) *
>> +			atomic_read(&kvm->online_vcpus);
>> +		break;
>> +	default:
>> +		return -ENXIO;
>> +	}
>> +
>> +	if (copy_from_user(dest, user, size))
>> +		return -EFAULT;
>> +
>> +	return 0;
>> +}
>> +
>> +static int kvm_arm_pvtime_set_attr(struct kvm_device *dev,
>> +				   struct kvm_device_attr *attr)
>> +{
>> +	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
>> +	u64 __user *user = (u64 __user *)attr->addr;
>> +	u64 paddr;
>> +	int ret;
>> +
>> +	switch (attr->group) {
>> +	case KVM_DEV_ARM_PV_TIME_PADDR:
>> +		if (get_user(paddr, user))
>> +			return -EFAULT;
>> +		if (paddr & 63)
>> +			return -EINVAL;
> 
> You should check whether the device fits into the IPA space for this
> guest, and whether it overlaps with anything else.

pvtime_map_pages() should fail in the case of overlap. That seems
sufficient to me - do you think we need something stronger?

>> +		switch (attr->attr) {
>> +		case KVM_DEV_ARM_PV_TIME_ST:
>> +			if (pvtime->st_base != GPA_INVALID)
>> +				return -EEXIST;
>> +			ret = pvtime_map_pages(dev->kvm, paddr, pvtime->st,
>> +					max_stolen_size());
> 
> Consider moving the size directly into pvtime_map_pages(), and dropping
> the pvtime->st parameter. All you need is kvm and paddr.

Will do.

Thanks,

Steve
Marc Zyngier Aug. 5, 2019, 4:28 p.m. UTC | #4
On 05/08/2019 17:10, Steven Price wrote:
> On 03/08/2019 13:51, Marc Zyngier wrote:
>> On Fri,  2 Aug 2019 15:50:14 +0100
>> Steven Price <steven.price@arm.com> wrote:
>>
>>> Allow user space to inform the KVM host where in the physical memory
>>> map the paravirtualized time structures should be located.
>>>
>>> A device is created which provides the base address of an array of
>>> Stolen Time (ST) structures, one for each VCPU. There must be (64 *
>>> total number of VCPUs) bytes of memory available at this location.
>>>
>>> The address is given in terms of the physical address visible to
>>> the guest and must be 64 byte aligned. The memory should be marked as
>>> reserved to the guest to stop it allocating it for other purposes.
>>
>> Why? You seem to be allocating the memory from the kernel, so as far as
>> the guest is concerned, this isn't generally usable memory.
> 
> I obviously didn't word it very well - that's what I meant. The "memory"
> that represents the stolen time structure shouldn't be shown to the
> guest as normal memory, but "reserved" for the purpose of stolen time.
> 
> To be honest it looks like I forgot to rewrite this commit message -
> which 64 byte alignment is all that the guest can rely on (because each
> vCPU has it's own structure), the actual array of structures needs to be
> page aligned to ensure we can safely map it into the guest.
> 
>>>
>>> Signed-off-by: Steven Price <steven.price@arm.com>
>>> ---
>>>  arch/arm64/include/asm/kvm_mmu.h  |   2 +
>>>  arch/arm64/include/uapi/asm/kvm.h |   6 +
>>>  arch/arm64/kvm/Makefile           |   1 +
>>>  include/uapi/linux/kvm.h          |   2 +
>>>  virt/kvm/arm/mmu.c                |  44 +++++++
>>>  virt/kvm/arm/pvtime.c             | 190 ++++++++++++++++++++++++++++++
>>>  6 files changed, 245 insertions(+)
>>>  create mode 100644 virt/kvm/arm/pvtime.c

[...]

>>> +static int kvm_arm_pvtime_set_attr(struct kvm_device *dev,
>>> +				   struct kvm_device_attr *attr)
>>> +{
>>> +	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
>>> +	u64 __user *user = (u64 __user *)attr->addr;
>>> +	u64 paddr;
>>> +	int ret;
>>> +
>>> +	switch (attr->group) {
>>> +	case KVM_DEV_ARM_PV_TIME_PADDR:
>>> +		if (get_user(paddr, user))
>>> +			return -EFAULT;
>>> +		if (paddr & 63)
>>> +			return -EINVAL;
>>
>> You should check whether the device fits into the IPA space for this
>> guest, and whether it overlaps with anything else.
> 
> pvtime_map_pages() should fail in the case of overlap. That seems
> sufficient to me - do you think we need something stronger?

Definitely. stage2_set_pte() won't fail for a non-IO overlapping
mapping, and will just treat it as guest memory. If this overlaps with a
memslot, we'll never be able to fault that page in, ending up with
interesting memory corruption... :-/

That's one of the reasons why I think option (2) in your earlier email
is an interesting one, as it sidesteps a whole lot of ugly and hard to
test corner cases.

Thanks,

	M.
Steven Price Aug. 7, 2019, 1:39 p.m. UTC | #5
On 03/08/2019 18:34, Marc Zyngier wrote:
> On Sat, 3 Aug 2019 13:51:13 +0100
> Marc Zyngier <maz@kernel.org> wrote:
> 
> [forgot that one]
> 
>> On Fri,  2 Aug 2019 15:50:14 +0100
>> Steven Price <steven.price@arm.com> wrote:
> 
> [...]
> 
>>> +static int __init kvm_pvtime_init(void)
>>> +{
>>> +	kvm_register_device_ops(&pvtime_ops, KVM_DEV_TYPE_ARM_PV_TIME);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +late_initcall(kvm_pvtime_init);
> 
> Why is it an initcall? So far, the only initcall we've used is the one
> that initializes KVM itself. Can't we just the device_ops just like we
> do for the vgic?

So would you prefer a direct call from init_subsystems() in
virt/kvm/arm/arm.c?

The benefit of initcall is just that it keeps the code self-contained.
In init_subsystems() I'd either need a #ifdef CONFIG_ARM64 or a dummy
function for arm.

Steve
Marc Zyngier Aug. 7, 2019, 1:51 p.m. UTC | #6
On 07/08/2019 14:39, Steven Price wrote:
> On 03/08/2019 18:34, Marc Zyngier wrote:
>> On Sat, 3 Aug 2019 13:51:13 +0100
>> Marc Zyngier <maz@kernel.org> wrote:
>>
>> [forgot that one]
>>
>>> On Fri,  2 Aug 2019 15:50:14 +0100
>>> Steven Price <steven.price@arm.com> wrote:
>>
>> [...]
>>
>>>> +static int __init kvm_pvtime_init(void)
>>>> +{
>>>> +	kvm_register_device_ops(&pvtime_ops, KVM_DEV_TYPE_ARM_PV_TIME);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +late_initcall(kvm_pvtime_init);
>>
>> Why is it an initcall? So far, the only initcall we've used is the one
>> that initializes KVM itself. Can't we just the device_ops just like we
>> do for the vgic?
> 
> So would you prefer a direct call from init_subsystems() in
> virt/kvm/arm/arm.c?

Yes. Consistency is important.

> The benefit of initcall is just that it keeps the code self-contained.
> In init_subsystems() I'd either need a #ifdef CONFIG_ARM64 or a dummy
> function for arm.

Having a dummy function for 32bit ARM is fine. Most of the code we add
to the 32bit port is made of empty stubs anyway.

Thanks,

	M.
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index befe37d4bc0e..88c8a4b2836f 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -157,6 +157,8 @@  int kvm_alloc_stage2_pgd(struct kvm *kvm);
 void kvm_free_stage2_pgd(struct kvm *kvm);
 int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 			  phys_addr_t pa, unsigned long size, bool writable);
+int kvm_phys_addr_memremap(struct kvm *kvm, phys_addr_t guest_ipa,
+			  phys_addr_t pa, unsigned long size, bool writable);
 
 int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run);
 
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 9a507716ae2f..95516a4198ea 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -367,6 +367,12 @@  struct kvm_vcpu_events {
 #define KVM_PSCI_RET_INVAL		PSCI_RET_INVALID_PARAMS
 #define KVM_PSCI_RET_DENIED		PSCI_RET_DENIED
 
+/* Device Control API: PV_TIME */
+#define KVM_DEV_ARM_PV_TIME_PADDR	0
+#define  KVM_DEV_ARM_PV_TIME_ST		0
+#define KVM_DEV_ARM_PV_TIME_STATE_SIZE	1
+#define KVM_DEV_ARM_PV_TIME_STATE	2
+
 #endif
 
 #endif /* __ARM_KVM_H__ */
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 73dce4d47d47..5ffbdc39e780 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -14,6 +14,7 @@  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/e
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hypercalls.o
+kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/pvtime.o
 
 kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
 kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index a7c19540ce21..04bffafa0708 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1222,6 +1222,8 @@  enum kvm_device_type {
 #define KVM_DEV_TYPE_ARM_VGIC_ITS	KVM_DEV_TYPE_ARM_VGIC_ITS
 	KVM_DEV_TYPE_XIVE,
 #define KVM_DEV_TYPE_XIVE		KVM_DEV_TYPE_XIVE
+	KVM_DEV_TYPE_ARM_PV_TIME,
+#define KVM_DEV_TYPE_ARM_PV_TIME	KVM_DEV_TYPE_ARM_PV_TIME
 	KVM_DEV_TYPE_MAX,
 };
 
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 38b4c910b6c3..be28a4aee451 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1368,6 +1368,50 @@  int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 	return ret;
 }
 
+/**
+ * kvm_phys_addr_memremap - map a memory range to guest IPA
+ *
+ * @kvm:	The KVM pointer
+ * @guest_ipa:	The IPA at which to insert the mapping
+ * @pa:		The physical address of the memory
+ * @size:	The size of the mapping
+ */
+int kvm_phys_addr_memremap(struct kvm *kvm, phys_addr_t guest_ipa,
+			  phys_addr_t pa, unsigned long size, bool writable)
+{
+	phys_addr_t addr, end;
+	int ret = 0;
+	unsigned long pfn;
+	struct kvm_mmu_memory_cache cache = { 0, };
+
+	end = (guest_ipa + size + PAGE_SIZE - 1) & PAGE_MASK;
+	pfn = __phys_to_pfn(pa);
+
+	for (addr = guest_ipa; addr < end; addr += PAGE_SIZE) {
+		pte_t pte = pfn_pte(pfn, PAGE_S2);
+
+		if (writable)
+			pte = kvm_s2pte_mkwrite(pte);
+
+		ret = mmu_topup_memory_cache(&cache,
+					     kvm_mmu_cache_min_pages(kvm),
+					     KVM_NR_MEM_OBJS);
+		if (ret)
+			goto out;
+		spin_lock(&kvm->mmu_lock);
+		ret = stage2_set_pte(kvm, &cache, addr, &pte, 0);
+		spin_unlock(&kvm->mmu_lock);
+		if (ret)
+			goto out;
+
+		pfn++;
+	}
+
+out:
+	mmu_free_memory_cache(&cache);
+	return ret;
+}
+
 static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
 {
 	kvm_pfn_t pfn = *pfnp;
diff --git a/virt/kvm/arm/pvtime.c b/virt/kvm/arm/pvtime.c
new file mode 100644
index 000000000000..9051bc07eae1
--- /dev/null
+++ b/virt/kvm/arm/pvtime.c
@@ -0,0 +1,190 @@ 
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2019 Arm Ltd.
+
+#include <linux/kvm_host.h>
+#include <asm/kvm_mmu.h>
+
+/* We currently only support PV time on ARM64 */
+#ifdef CONFIG_ARM64
+
+#include <asm/pvclock-abi.h>
+
+static int max_stolen_size(void)
+{
+	int size = KVM_MAX_VCPUS * sizeof(struct pvclock_vcpu_stolen_time_info);
+
+	return ALIGN(size, PAGE_SIZE);
+}
+
+static int kvm_arm_pvtime_create(struct kvm_device *dev, u32 type)
+{
+	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
+
+	pvtime->st = alloc_pages_exact(max_stolen_size(),
+				       GFP_KERNEL | __GFP_ZERO);
+	if (!pvtime->st)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void kvm_arm_pvtime_destroy(struct kvm_device *dev)
+{
+	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
+
+	pvtime->st_base = GPA_INVALID;
+	free_pages_exact(pvtime->st, max_stolen_size());
+	kfree(dev);
+}
+
+static int pvtime_map_pages(struct kvm *kvm, gpa_t guest_paddr,
+			    void *kaddr, int size)
+{
+	return kvm_phys_addr_memremap(kvm, guest_paddr,
+			virt_to_phys(kaddr),
+			size, false);
+}
+
+static int pvtime_save_state(struct kvm *kvm, u64 type, void __user *user)
+{
+	void *source;
+	size_t size;
+
+	switch (type) {
+	case KVM_DEV_ARM_PV_TIME_ST:
+		source = kvm->arch.pvtime.st;
+		size = sizeof(struct pvclock_vcpu_stolen_time_info) *
+			atomic_read(&kvm->online_vcpus);
+		break;
+	default:
+		return -ENXIO;
+	}
+
+	if (copy_to_user(user, source, size))
+		return -EFAULT;
+	return 0;
+}
+
+static int pvtime_restore_state(struct kvm *kvm, u64 type, void __user *user)
+{
+	void *dest;
+	size_t size;
+
+	switch (type) {
+	case KVM_DEV_ARM_PV_TIME_ST:
+		dest = kvm->arch.pvtime.st;
+		size = sizeof(struct pvclock_vcpu_stolen_time_info) *
+			atomic_read(&kvm->online_vcpus);
+		break;
+	default:
+		return -ENXIO;
+	}
+
+	if (copy_from_user(dest, user, size))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int kvm_arm_pvtime_set_attr(struct kvm_device *dev,
+				   struct kvm_device_attr *attr)
+{
+	struct kvm_arch_pvtime *pvtime = &dev->kvm->arch.pvtime;
+	u64 __user *user = (u64 __user *)attr->addr;
+	u64 paddr;
+	int ret;
+
+	switch (attr->group) {
+	case KVM_DEV_ARM_PV_TIME_PADDR:
+		if (get_user(paddr, user))
+			return -EFAULT;
+		if (paddr & 63)
+			return -EINVAL;
+		switch (attr->attr) {
+		case KVM_DEV_ARM_PV_TIME_ST:
+			if (pvtime->st_base != GPA_INVALID)
+				return -EEXIST;
+			ret = pvtime_map_pages(dev->kvm, paddr, pvtime->st,
+					max_stolen_size());
+			if (ret)
+				return ret;
+			pvtime->st_base = paddr;
+			return 0;
+		}
+		break;
+	case KVM_DEV_ARM_PV_TIME_STATE_SIZE:
+		return -EPERM;
+	case KVM_DEV_ARM_PV_TIME_STATE:
+		return pvtime_restore_state(dev->kvm, attr->attr, user);
+	}
+	return -ENXIO;
+}
+
+static int kvm_arm_pvtime_get_attr(struct kvm_device *dev,
+				   struct kvm_device_attr *attr)
+{
+	u64 __user *user = (u64 __user *)attr->addr;
+	u32 size;
+
+	switch (attr->group) {
+	case KVM_DEV_ARM_PV_TIME_PADDR:
+		switch (attr->attr) {
+		case KVM_DEV_ARM_PV_TIME_ST:
+			if (put_user(dev->kvm->arch.pvtime.st_base, user))
+				return -EFAULT;
+			return 0;
+		}
+		break;
+	case KVM_DEV_ARM_PV_TIME_STATE_SIZE:
+		switch (attr->attr) {
+		case KVM_DEV_ARM_PV_TIME_ST:
+			size = sizeof(struct pvclock_vcpu_stolen_time_info);
+			size *= atomic_read(&dev->kvm->online_vcpus);
+			break;
+		default:
+			return -ENXIO;
+		}
+		if (put_user(size, user))
+			return -EFAULT;
+		return 0;
+	case KVM_DEV_ARM_PV_TIME_STATE:
+		return pvtime_save_state(dev->kvm, attr->attr, user);
+	}
+	return -ENXIO;
+}
+
+static int kvm_arm_pvtime_has_attr(struct kvm_device *dev,
+				   struct kvm_device_attr *attr)
+{
+	switch (attr->group) {
+	case KVM_DEV_ARM_PV_TIME_PADDR:
+	case KVM_DEV_ARM_PV_TIME_STATE_SIZE:
+	case KVM_DEV_ARM_PV_TIME_STATE:
+		switch (attr->attr) {
+		case KVM_DEV_ARM_PV_TIME_ST:
+			return 0;
+		}
+		break;
+	}
+	return -ENXIO;
+}
+
+static const struct kvm_device_ops pvtime_ops = {
+	"Arm PV time",
+	.create = kvm_arm_pvtime_create,
+	.destroy = kvm_arm_pvtime_destroy,
+	.set_attr = kvm_arm_pvtime_set_attr,
+	.get_attr = kvm_arm_pvtime_get_attr,
+	.has_attr = kvm_arm_pvtime_has_attr
+};
+
+static int __init kvm_pvtime_init(void)
+{
+	kvm_register_device_ops(&pvtime_ops, KVM_DEV_TYPE_ARM_PV_TIME);
+
+	return 0;
+}
+
+late_initcall(kvm_pvtime_init);
+
+#endif