[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 3/5] x86/PV: _PAGE_RW changes may take fast path of mod_l[234]_entry()
On 11.01.2021 12:08, Roger Pau Monné wrote: > On Tue, Nov 03, 2020 at 11:57:10AM +0100, Jan Beulich wrote: >> The only time _PAGE_RW matters when validating an L2 or higher entry is >> when a linear page table is tried to be installed. Therefore when we >> disallow such at build time, we can allow _PAGE_RW changes to take the >> fast paths there. > > I think it would be helpful to note why PDEs with linear page tables > aren't allowed to have the RW bit set, likely here and in the comment > below. I've changed the description to "The only time _PAGE_RW matters when validating an L2 or higher entry is when a linear page table is tried to be installed (see the comment ahead of define_get_linear_pagetable()). Therefore when we disallow such at build time, we can allow _PAGE_RW changes to take the fast paths there." Considering there already is a code comment explaining this, I'm less convinced of also editing the comment. An option might be to move up the #define-s next to define_get_linear_pagetable(), but imo this should then involve moving FASTPATH_FLAG_WHITELIST as well. Jan
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