Messages in this thread | | | Date | Wed, 08 Mar 2023 00:13:24 +0000 | Subject | Re: [PATCH v10 9/9] KVM: Enable and expose KVM_MEM_PRIVATE | From | Ackerley Tng <> |
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Chao Peng <chao.p.peng@linux.intel.com> writes:
> On Sat, Jan 14, 2023 at 12:01:01AM +0000, Sean Christopherson wrote: >> On Fri, Dec 02, 2022, Chao Peng wrote: > ... >> Strongly prefer to use similar logic to existing code that detects wraps:
>> mem->restricted_offset + mem->memory_size < mem->restricted_offset
>> This is also where I'd like to add the "gfn is aligned to offset" check, >> though >> my brain is too fried to figure that out right now.
> Used count_trailing_zeros() for this TODO, unsure we have other better > approach.
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index afc8c26fa652..fd34c5f7cd2f 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -56,6 +56,7 @@ > #include <asm/processor.h> > #include <asm/ioctl.h> > #include <linux/uaccess.h> > +#include <linux/count_zeros.h>
> #include "coalesced_mmio.h" > #include "async_pf.h" > @@ -2087,6 +2088,19 @@ static bool kvm_check_memslot_overlap(struct > kvm_memslots *slots, int id, > return false; > }
> +/* > + * Return true when ALIGNMENT(offset) >= ALIGNMENT(gpa). > + */ > +static bool kvm_check_rmem_offset_alignment(u64 offset, u64 gpa) > +{ > + if (!offset) > + return true; > + if (!gpa) > + return false; > + > + return !!(count_trailing_zeros(offset) >= count_trailing_zeros(gpa));
Perhaps we could do something like
#define lowest_set_bit(val) (val & -val)
and use
return lowest_set_bit(offset) >= lowest_set_bit(gpa);
Please help me to understand: why must ALIGNMENT(offset) >= ALIGNMENT(gpa)? Why is it not sufficient to have both gpa and offset be aligned to PAGE_SIZE?
> +} > + > /* > * Allocate some memory and give it an address in the guest physical > address > * space. > @@ -2128,7 +2142,8 @@ int __kvm_set_memory_region(struct kvm *kvm, > if (mem->flags & KVM_MEM_PRIVATE && > (mem->restrictedmem_offset & (PAGE_SIZE - 1) || > mem->restrictedmem_offset + mem->memory_size < > mem->restrictedmem_offset || > - 0 /* TODO: require gfn be aligned with restricted offset */)) > + !kvm_check_rmem_offset_alignment(mem->restrictedmem_offset, > + mem->guest_phys_addr))) > return -EINVAL; > if (as_id >= kvm_arch_nr_memslot_as_ids(kvm) || id >= KVM_MEM_SLOTS_NUM) > return -EINVAL;
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