On Tue, Jun 04, 2019 at 06:41:29AM -0600, Jan Beulich wrote:
> Rather than checking that a page table is _not_ "owned" by the fake COW
> domain, check that it's owned by the domain actually wanting to install
> it.
>
> Switch away from BUG_ON() at the same time.
>
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
Reviewed-by: Roger Pau Monné <roger....@citrix.com>
> ---
> v2: Split out from larger patch to make further adjustments.
> ---
> Thinking about it I wonder why we have such a check here and no-where
> else. An alternative would seem to be to simply drop the BUG_ON().
>
> --- a/xen/arch/x86/pv/emul-priv-op.c
> +++ b/xen/arch/x86/pv/emul-priv-op.c
> @@ -706,7 +706,7 @@ static int read_cr(unsigned int reg, uns
>
> case 3: /* Read CR3 */
> {
> - const struct domain *currd = curr->domain;
> + struct domain *currd = curr->domain;
> mfn_t mfn;
>
> if ( !is_pv_32bit_domain(currd) )
> @@ -723,8 +723,14 @@ static int read_cr(unsigned int reg, uns
> unmap_domain_page(pl4e);
> *val = compat_pfn_to_cr3(mfn_to_gmfn(currd, mfn_x(mfn)));
> }
> - /* PTs should not be shared */
> - BUG_ON(page_get_owner(mfn_to_page(mfn)) == dom_cow);
> +
> + /* PTs should be owned by their domains */
> + if ( page_get_owner(mfn_to_page(mfn)) != currd )
> + {
> + ASSERT_UNREACHABLE();
> + domain_crash(currd);
I wonder whether you could keep currd as const and just use
curr->domain here.
Thanks, Roger.
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