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SubjectRe: [PATCH] x86/mm: Rewrite sme_populate_pgd() in a more sensible way
On Mon, Dec 04, 2017 at 05:39:31PM +0000, 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.
>
> Any objections on this:

Oops. Screwed up whitespaces.

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 65e0d68f863f..f7b6c7972884 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;
+ 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;
}

void __init sme_encrypt_kernel(void)
--
Kirill A. Shutemov
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