Messages in this thread | | | Subject | Re: [PATCH] x86/mm: Rewrite sme_populate_pgd() in a more sensible way | From | Tom Lendacky <> | Date | Fri, 8 Dec 2017 08:37:43 -0600 |
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On 12/4/2017 11:39 AM, Kirill A. Shutemov wrote: > On Mon, Dec 04, 2017 at 04:34:45PM +0000, Kirill A. Shutemov wrote: >> On Mon, Dec 04, 2017 at 04:00:26PM +0000, Tom Lendacky wrote: >>> On 12/4/2017 8:57 AM, Kirill A. Shutemov wrote: >>>> On Mon, Dec 04, 2017 at 08:19:11AM -0600, Tom Lendacky wrote: >>>>> On 12/4/2017 5:23 AM, Kirill A. Shutemov wrote: >>>>>> sme_populate_pgd() open-codes a lot of things that are not needed to be >>>>>> open-coded. >>>>>> >>>>>> Let's rewrite it in a more stream-lined way. >>>>>> >>>>>> This would also buy us boot-time switching between support between >>>>>> paging modes, when rest of the pieces will be upstream. >>>>> >>>>> Hi Kirill, >>>>> >>>>> Unfortunately, some of these can't be changed. The use of p4d_offset(), >>>>> pud_offset(), etc., use non-identity mapped virtual addresses which cause >>>>> failures at this point of the boot process. >>>> >>>> Wat? Virtual address is virtual address. p?d_offset() doesn't care about >>>> what mapping you're using. >>> >>> Yes it does. For example, pmd_offset() issues a pud_page_addr() call, >>> which does a __va() returning a non-identity mapped address (0xffff88...). >>> Only identity mapped virtual addresses have been setup at this point, so >>> the use of that virtual address panics the kernel. >> >> Stupid me. You are right. >> >> What about something like this: > > sme_pgtable_calc() also looks unnecessary complex.
I have no objections to improving this (although I just submitted a patch that modifies this area, so this will have to be updated now).
> > Any objections on this: > > diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c > index 65e0d68f863f..59b7d7ba9b37 100644 > --- a/arch/x86/mm/mem_encrypt.c > +++ b/arch/x86/mm/mem_encrypt.c > @@ -548,8 +548,7 @@ static void __init *sme_populate_pgd(pgd_t *pgd_base, void *pgtable_area, > > static unsigned long __init sme_pgtable_calc(unsigned long len) > { > - unsigned long p4d_size, pud_size, pmd_size; > - unsigned long total; > + unsigned long entries, tables; > > /* > * Perform a relatively simplistic calculation of the pagetable > @@ -559,41 +558,25 @@ static unsigned long __init sme_pgtable_calc(unsigned long len) > * mappings. Incrementing the count for each covers the case where > * the addresses cross entries. > */ > - if (IS_ENABLED(CONFIG_X86_5LEVEL)) { > - p4d_size = (ALIGN(len, PGDIR_SIZE) / PGDIR_SIZE) + 1; > - p4d_size *= sizeof(p4d_t) * PTRS_PER_P4D; > - pud_size = (ALIGN(len, P4D_SIZE) / P4D_SIZE) + 1; > - pud_size *= sizeof(pud_t) * PTRS_PER_PUD; > - } else { > - p4d_size = 0; > - pud_size = (ALIGN(len, PGDIR_SIZE) / PGDIR_SIZE) + 1; > - pud_size *= sizeof(pud_t) * PTRS_PER_PUD; > - } > - pmd_size = (ALIGN(len, PUD_SIZE) / PUD_SIZE) + 1; > - pmd_size *= sizeof(pmd_t) * PTRS_PER_PMD; > > - total = p4d_size + pud_size + pmd_size; > + entries = (DIV_ROUND_UP(len, PGDIR_SIZE) + 1) * PAGE_SIZE;
I stayed away from using PAGE_SIZE directly because other areas/files used the sizeof() * PTRS_PER_ and I was trying to be consistent. Not that the size of a page table is ever likely to change, but maybe defining a macro (similar to the one in mm/pgtable.c) would be best rather than using PAGE_SIZE directly. Not required, just my opinion.
> + if (PTRS_PER_P4D > 1) > + entries += (DIV_ROUND_UP(len, P4D_SIZE) + 1) * PAGE_SIZE; > + entries += (DIV_ROUND_UP(len, PUD_SIZE) + 1) * PAGE_SIZE; > + entries += (DIV_ROUND_UP(len, PMD_SIZE) + 1) * PAGE_SIZE; > > /* > * Now calculate the added pagetable structures needed to populate > * the new pagetables. > */ > - if (IS_ENABLED(CONFIG_X86_5LEVEL)) { > - p4d_size = ALIGN(total, PGDIR_SIZE) / PGDIR_SIZE; > - p4d_size *= sizeof(p4d_t) * PTRS_PER_P4D; > - pud_size = ALIGN(total, P4D_SIZE) / P4D_SIZE; > - pud_size *= sizeof(pud_t) * PTRS_PER_PUD; > - } else { > - p4d_size = 0; > - pud_size = ALIGN(total, PGDIR_SIZE) / PGDIR_SIZE; > - pud_size *= sizeof(pud_t) * PTRS_PER_PUD; > - } > - pmd_size = ALIGN(total, PUD_SIZE) / PUD_SIZE; > - pmd_size *= sizeof(pmd_t) * PTRS_PER_PMD; > > - total += p4d_size + pud_size + pmd_size; > + tables = DIV_ROUND_UP(entries, PGDIR_SIZE) * PAGE_SIZE; > + if (PTRS_PER_P4D > 1) > + tables += DIV_ROUND_UP(entries, P4D_SIZE) * PAGE_SIZE; > + tables += DIV_ROUND_UP(entries, PUD_SIZE) * PAGE_SIZE; > + tables += DIV_ROUND_UP(entries, PMD_SIZE) * PAGE_SIZE; > > - return total; > + return entries + tables; > }
It all looks reasonable, but I won't be able to test for the next few days, though.
Thanks, Tom
> > void __init sme_encrypt_kernel(void) >
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