Re: [PATCH v4 2/2] kvm/arm64: Try stage2 block mapping for host device MMIO
Hi Marc,
On 2021/4/16 22:44, Marc Zyngier wrote:
> On Thu, 15 Apr 2021 15:08:09 +0100,
> Keqian Zhu wrote:
>>
>> Hi Marc,
>>
>> On 2021/4/15 22:03, Keqian Zhu wrote:
>>> The MMIO region of a device maybe huge (GB level), try to use
>>> block mapping in stage2 to speedup both map and unmap.
>>>
>>> Compared to normal memory mapping, we should consider two more
>>> points when try block mapping for MMIO region:
>>>
>>> 1. For normal memory mapping, the PA(host physical address) and
>>> HVA have same alignment within PUD_SIZE or PMD_SIZE when we use
>>> the HVA to request hugepage, so we don't need to consider PA
>>> alignment when verifing block mapping. But for device memory
>>> mapping, the PA and HVA may have different alignment.
>>>
>>> 2. For normal memory mapping, we are sure hugepage size properly
>>> fit into vma, so we don't check whether the mapping size exceeds
>>> the boundary of vma. But for device memory mapping, we should pay
>>> attention to this.
>>>
>>> This adds get_vma_page_shift() to get page shift for both normal
>>> memory and device MMIO region, and check these two points when
>>> selecting block mapping size for MMIO region.
>>>
>>> Signed-off-by: Keqian Zhu
>>> ---
>>> arch/arm64/kvm/mmu.c | 61
>>> 1 file changed, 51 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>>> index c59af5ca01b0..5a1cc7751e6d 100644
>>> --- a/arch/arm64/kvm/mmu.c
>>> +++ b/arch/arm64/kvm/mmu.c
>>> @@ -738,6 +738,35 @@ transparent_hugepage_adjust(struct kvm_memory_slot
>>> *memslot,
>>> return PAGE_SIZE;
>>> }
>>>
[...]
>>> + /*
>>> +* logging_active is guaranteed to never be true for VM_PFNMAP
>>> +* memslots.
>>> +*/
>>> + if (logging_active) {
>>> force_pte = true;
>>> vma_shift = PAGE_SHIFT;
>>> + } else {
>>> + vma_shift = get_vma_page_shift(vma, hva);
>>> }
>> I use a if/else manner in v4, please check that. Thanks very much!
>
> That's fine. However, it is getting a bit late for 5.13, and we don't
> have much time to left it simmer in -next. I'll probably wait until
> after the merge window to pick it up.
OK, no problem. Thanks! :)
BRs,
Keqian
Re: [PATCH v4 2/2] kvm/arm64: Try stage2 block mapping for host device MMIO
On Thu, 15 Apr 2021 15:08:09 +0100,
Keqian Zhu wrote:
>
> Hi Marc,
>
> On 2021/4/15 22:03, Keqian Zhu wrote:
> > The MMIO region of a device maybe huge (GB level), try to use
> > block mapping in stage2 to speedup both map and unmap.
> >
> > Compared to normal memory mapping, we should consider two more
> > points when try block mapping for MMIO region:
> >
> > 1. For normal memory mapping, the PA(host physical address) and
> > HVA have same alignment within PUD_SIZE or PMD_SIZE when we use
> > the HVA to request hugepage, so we don't need to consider PA
> > alignment when verifing block mapping. But for device memory
> > mapping, the PA and HVA may have different alignment.
> >
> > 2. For normal memory mapping, we are sure hugepage size properly
> > fit into vma, so we don't check whether the mapping size exceeds
> > the boundary of vma. But for device memory mapping, we should pay
> > attention to this.
> >
> > This adds get_vma_page_shift() to get page shift for both normal
> > memory and device MMIO region, and check these two points when
> > selecting block mapping size for MMIO region.
> >
> > Signed-off-by: Keqian Zhu
> > ---
> > arch/arm64/kvm/mmu.c | 61
> > 1 file changed, 51 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index c59af5ca01b0..5a1cc7751e6d 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -738,6 +738,35 @@ transparent_hugepage_adjust(struct kvm_memory_slot
> > *memslot,
> > return PAGE_SIZE;
> > }
> >
> > +static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long
> > hva)
> > +{
> > + unsigned long pa;
> > +
> > + if (is_vm_hugetlb_page(vma) && !(vma->vm_flags & VM_PFNMAP))
> > + return huge_page_shift(hstate_vma(vma));
> > +
> > + if (!(vma->vm_flags & VM_PFNMAP))
> > + return PAGE_SHIFT;
> > +
> > + VM_BUG_ON(is_vm_hugetlb_page(vma));
> > +
> > + pa = (vma->vm_pgoff << PAGE_SHIFT) + (hva - vma->vm_start);
> > +
> > +#ifndef __PAGETABLE_PMD_FOLDED
> > + if ((hva & (PUD_SIZE - 1)) == (pa & (PUD_SIZE - 1)) &&
> > + ALIGN_DOWN(hva, PUD_SIZE) >= vma->vm_start &&
> > + ALIGN(hva, PUD_SIZE) <= vma->vm_end)
> > + return PUD_SHIFT;
> > +#endif
> > +
> > + if ((hva & (PMD_SIZE - 1)) == (pa & (PMD_SIZE - 1)) &&
> > + ALIGN_DOWN(hva, PMD_SIZE) >= vma->vm_start &&
> > + ALIGN(hva, PMD_SIZE) <= vma->vm_end)
> > + return PMD_SHIFT;
> > +
> > + return PAGE_SHIFT;
> > +}
> > +
> > static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> > struct kvm_memory_slot *memslot, unsigned long hva,
> > unsigned long fault_status)
> > @@ -769,7 +798,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu,
> > phys_addr_t fault_ipa,
> > return -EFAULT;
> > }
> >
> > - /* Let's check if we will get back a huge page backed by hugetlbfs */
> > + /*
> > +* Let's check if we will get back a huge page backed by hugetlbfs, or
> > +* get block mapping for device MMIO region.
> > +*/
> > mmap_read_lock(current->mm);
> > vma = find_vma_intersection(current->mm, hva, hva + 1);
> > if (unlikely(!vma)) {
> > @@ -778,15 +810,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu,
> > phys_addr_t fault_ipa,
> > return -EFAULT;
> > }
> >
> > - if (is_vm_hugetlb_page(vma))
> > - vma_shift = huge_page_shift(hstate_vma(vma));
> > - else
> > - vma_shift = PAGE_SHIFT;
> > -
> > - if (logging_active ||
> > - (vma->vm_flags & VM_PFNMAP)) {
> > + /*
> > +* logging_active is guaranteed to never be true for VM_PFNMAP
> > +* memslots.
> > +*/
> > + if (logging_active) {
> > force_pte = true;
> > vma_shift = PAGE_SHIFT;
> > + } else {
> > + vma_shift = get_vma_page_shift(vma, hva);
> > }
> I use a if/else manner in v4, please check that. Thanks very much!
That's fine. However, it is getting a bit late for 5.13, and we don't
have much time to left it simmer in -next. I'll probably wait until
after the merge window to pick it up.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
Re: [PATCH v4 2/2] kvm/arm64: Try stage2 block mapping for host device MMIO
Hi Marc,
On 2021/4/15 22:03, Keqian Zhu wrote:
> The MMIO region of a device maybe huge (GB level), try to use
> block mapping in stage2 to speedup both map and unmap.
>
> Compared to normal memory mapping, we should consider two more
> points when try block mapping for MMIO region:
>
> 1. For normal memory mapping, the PA(host physical address) and
> HVA have same alignment within PUD_SIZE or PMD_SIZE when we use
> the HVA to request hugepage, so we don't need to consider PA
> alignment when verifing block mapping. But for device memory
> mapping, the PA and HVA may have different alignment.
>
> 2. For normal memory mapping, we are sure hugepage size properly
> fit into vma, so we don't check whether the mapping size exceeds
> the boundary of vma. But for device memory mapping, we should pay
> attention to this.
>
> This adds get_vma_page_shift() to get page shift for both normal
> memory and device MMIO region, and check these two points when
> selecting block mapping size for MMIO region.
>
> Signed-off-by: Keqian Zhu
> ---
> arch/arm64/kvm/mmu.c | 61
> 1 file changed, 51 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index c59af5ca01b0..5a1cc7751e6d 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -738,6 +738,35 @@ transparent_hugepage_adjust(struct kvm_memory_slot
> *memslot,
> return PAGE_SIZE;
> }
>
> +static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva)
> +{
> + unsigned long pa;
> +
> + if (is_vm_hugetlb_page(vma) && !(vma->vm_flags & VM_PFNMAP))
> + return huge_page_shift(hstate_vma(vma));
> +
> + if (!(vma->vm_flags & VM_PFNMAP))
> + return PAGE_SHIFT;
> +
> + VM_BUG_ON(is_vm_hugetlb_page(vma));
> +
> + pa = (vma->vm_pgoff << PAGE_SHIFT) + (hva - vma->vm_start);
> +
> +#ifndef __PAGETABLE_PMD_FOLDED
> + if ((hva & (PUD_SIZE - 1)) == (pa & (PUD_SIZE - 1)) &&
> + ALIGN_DOWN(hva, PUD_SIZE) >= vma->vm_start &&
> + ALIGN(hva, PUD_SIZE) <= vma->vm_end)
> + return PUD_SHIFT;
> +#endif
> +
> + if ((hva & (PMD_SIZE - 1)) == (pa & (PMD_SIZE - 1)) &&
> + ALIGN_DOWN(hva, PMD_SIZE) >= vma->vm_start &&
> + ALIGN(hva, PMD_SIZE) <= vma->vm_end)
> + return PMD_SHIFT;
> +
> + return PAGE_SHIFT;
> +}
> +
> static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> struct kvm_memory_slot *memslot, unsigned long hva,
> unsigned long fault_status)
> @@ -769,7 +798,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu,
> phys_addr_t fault_ipa,
> return -EFAULT;
> }
>
> - /* Let's check if we will get back a huge page backed by hugetlbfs */
> + /*
> + * Let's check if we will get back a huge page backed by hugetlbfs, or
> + * get block mapping for device MMIO region.
> + */
> mmap_read_lock(current->mm);
> vma = find_vma_intersection(current->mm, hva, hva + 1);
> if (unlikely(!vma)) {
> @@ -778,15 +810,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu,
> phys_addr_t fault_ipa,
> return -EFAULT;
> }
>
> - if (is_vm_hugetlb_page(vma))
> - vma_shift = huge_page_shift(hstate_vma(vma));
> - else
> - vma_shift = PAGE_SHIFT;
> -
> - if (logging_active ||
> - (vma->vm_flags & VM_PFNMAP)) {
> + /*
> + * logging_active is guaranteed to never be true for VM_PFNMAP
> + * memslots.
> + */
> + if (logging_active) {
> force_pte = true;
> vma_shift = PAGE_SHIFT;
> + } else {
> + vma_shift = get_vma_page_shift(vma, hva);
> }
I use a if/else manner in v4, please check that. Thanks very much!
BRs,
Keqian
>
> switch (vma_shift) {
> @@ -854,8 +886,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu,
> phys_addr_t fault_ipa,
> return -EFAULT;
>
> if (kvm_is_device_pfn(pfn)) {
> + /*
> + * If the page was identified as device early by looking at
> + * the VMA flags, vma_pagesize is already representing the
> + * largest quantity we can map. If instead it was mapped
> + * via gfn_to_pfn_prot(), vma_pagesize is set to PAGE_SIZE
> + * and must not be upgraded.
> + *
> + * In both cases, we don't let transparent_hugepage_adjust()
> + * change things at the last minute.
> + */
> device = true;
> - force_pte = true;
> } else if (logging_active && !write_fault) {
> /*
>* Only actually map the page as writable if this was a write
> @@ -876,7 +917,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu,
> phys_addr_t fault_ipa,
>* If we are not forced to use page mapping, check if we are
>
