lkml.org 
[lkml]   [2023]   [Mar]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH v10 9/9] KVM: Enable and expose KVM_MEM_PRIVATE
    From
    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;

    \
     
     \ /
      Last update: 2023-03-27 00:48    [W:4.126 / U:0.144 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site