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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/2] x86/mm: Use mfn_t for new_guest_cr3()
On Wed, Aug 30, 2017 at 1:19 PM, Andrew Cooper
<andrew.cooper3@xxxxxxxxxx> wrote:
> No functional change (as confirmed by diffing the assembly).
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
>
> For some reason best known to GCC, there is one single change:
>
> @@ -145835,7 +145835,7 @@
> ffff82d0802864f8: 85 c0 test %eax,%eax
> ffff82d0802864fa: 75 e0 jne ffff82d0802864dc
> <new_guest_cr3+0x7c>
> ffff82d0802864fc: 4c 8b ad 08 0b 00 00 mov 0xb08(%rbp),%r13
> -ffff82d080286503: 49 39 dd cmp %rbx,%r13
> +ffff82d080286503: 4c 39 eb cmp %r13,%rbx
> ffff82d080286506: 0f 84 74 01 00 00 je ffff82d080286680
> <new_guest_cr3+0x220>
> ffff82d08028650c: 41 f6 84 24 19 06 00 testb $0x8,0x619(%r12)
> ffff82d080286513: 00 08
>
> This is from the mfn_eq() alteration, and must be a side effect from using an
> inline function. The net result is still correct, as only the zero flag is
> checked.
> ---
> xen/arch/x86/mm.c | 35 ++++++++++++++++++-----------------
> xen/arch/x86/pv/emul-priv-op.c | 2 +-
> xen/include/asm-x86/mm.h | 2 +-
> 3 files changed, 20 insertions(+), 19 deletions(-)
>
> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
> index 1f23470..dc07b4f 100644
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -2772,23 +2772,23 @@ int vcpu_destroy_pagetables(struct vcpu *v)
> return rc != -EINTR ? rc : -ERESTART;
> }
>
> -int new_guest_cr3(unsigned long mfn)
> +int new_guest_cr3(mfn_t mfn)
> {
> struct vcpu *curr = current;
> struct domain *d = curr->domain;
> int rc;
> - unsigned long old_base_mfn;
> + mfn_t old_base_mfn;
>
> if ( is_pv_32bit_domain(d) )
> {
> - unsigned long gt_mfn = pagetable_get_pfn(curr->arch.guest_table);
> - l4_pgentry_t *pl4e = map_domain_page(_mfn(gt_mfn));
> + mfn_t mmfn = pagetable_get_mfn(curr->arch.guest_table);
> + l4_pgentry_t *pl4e = map_domain_page(mmfn);
>
> rc = mod_l4_entry(pl4e,
> - l4e_from_pfn(mfn,
> + l4e_from_mfn(mfn,
> (_PAGE_PRESENT | _PAGE_RW |
> _PAGE_USER | _PAGE_ACCESSED)),
> - gt_mfn, 0, curr);
> + mfn_x(mmfn), 0, curr);
> unmap_domain_page(pl4e);
> switch ( rc )
> {
> @@ -2800,7 +2800,7 @@ int new_guest_cr3(unsigned long mfn)
> default:
> gdprintk(XENLOG_WARNING,
> "Error while installing new compat baseptr %" PRI_mfn
> "\n",
> - mfn);
> + mfn_x(mfn));
> return rc;
> }
>
> @@ -2814,20 +2814,20 @@ int new_guest_cr3(unsigned long mfn)
> if ( unlikely(rc) )
> return rc;
>
> - old_base_mfn = pagetable_get_pfn(curr->arch.guest_table);
> + old_base_mfn = pagetable_get_mfn(curr->arch.guest_table);
> /*
> * This is particularly important when getting restarted after the
> * previous attempt got preempted in the put-old-MFN phase.
> */
> - if ( old_base_mfn == mfn )
> + if ( mfn_eq(old_base_mfn, mfn) )
> {
> write_ptbase(curr);
> return 0;
> }
>
> rc = paging_mode_refcounts(d)
> - ? (get_page_from_mfn(_mfn(mfn), d) ? 0 : -EINVAL)
> - : get_page_and_type_from_mfn(_mfn(mfn), PGT_root_page_table, d, 0,
> 1);
> + ? (get_page_from_mfn(mfn, d) ? 0 : -EINVAL)
> + : get_page_and_type_from_mfn(mfn, PGT_root_page_table, d, 0, 1);
> switch ( rc )
> {
> case 0:
> @@ -2837,22 +2837,23 @@ int new_guest_cr3(unsigned long mfn)
> return -ERESTART;
> default:
> gdprintk(XENLOG_WARNING,
> - "Error while installing new baseptr %" PRI_mfn "\n", mfn);
> + "Error while installing new baseptr %" PRI_mfn "\n",
> + mfn_x(mfn));
> return rc;
> }
>
> invalidate_shadow_ldt(curr, 0);
>
> if ( !VM_ASSIST(d, m2p_strict) && !paging_mode_refcounts(d) )
> - fill_ro_mpt(_mfn(mfn));
> - curr->arch.guest_table = pagetable_from_pfn(mfn);
> + fill_ro_mpt(mfn);
> + curr->arch.guest_table = pagetable_from_mfn(mfn);
> update_cr3(curr);
>
> write_ptbase(curr);
>
> - if ( likely(old_base_mfn != 0) )
> + if ( likely(mfn_x(old_base_mfn) != 0) )
> {
> - struct page_info *page = mfn_to_page(_mfn(old_base_mfn));
> + struct page_info *page = mfn_to_page(old_base_mfn);
>
> if ( paging_mode_refcounts(d) )
> put_page(page);
> @@ -3180,7 +3181,7 @@ long do_mmuext_op(
> else if ( unlikely(paging_mode_translate(currd)) )
> rc = -EINVAL;
> else
> - rc = new_guest_cr3(op.arg1.mfn);
> + rc = new_guest_cr3(_mfn(op.arg1.mfn));
> break;
>
> case MMUEXT_NEW_USER_BASEPTR: {
> diff --git a/xen/arch/x86/pv/emul-priv-op.c b/xen/arch/x86/pv/emul-priv-op.c
> index af1624a..54a63c2 100644
> --- a/xen/arch/x86/pv/emul-priv-op.c
> +++ b/xen/arch/x86/pv/emul-priv-op.c
> @@ -774,7 +774,7 @@ static int priv_op_write_cr(unsigned int reg, unsigned
> long val,
> page = get_page_from_gfn(currd, gfn, NULL, P2M_ALLOC);
> if ( !page )
> break;
> - rc = new_guest_cr3(mfn_x(page_to_mfn(page)));
> + rc = new_guest_cr3(page_to_mfn(page));
> put_page(page);
>
> switch ( rc )
> diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
> index ec7ce3c..4c03a33 100644
> --- a/xen/include/asm-x86/mm.h
> +++ b/xen/include/asm-x86/mm.h
> @@ -539,7 +539,7 @@ void audit_domains(void);
>
> #endif
>
> -int new_guest_cr3(unsigned long pfn);
> +int new_guest_cr3(mfn_t mfn);
> void make_cr3(struct vcpu *v, unsigned long mfn);
> void update_cr3(struct vcpu *v);
> int vcpu_destroy_pagetables(struct vcpu *);
> --
> 2.1.4
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> https://lists.xen.org/xen-devel
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