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SubjectRe: [PATCH] x86/mm: Rewrite sme_populate_pgd() in a more sensible way
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:

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index d9a9e9fc75dd..65e0d68f863f 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -12,6 +12,23 @@

#define DISABLE_BRANCH_PROFILING

+/*
+ * Since we're dealing with identity mappings, physical and virtual
+ * addresses are the same, so override these defines which are ultimately
+ * used by the headers in misc.h.
+ */
+#define __pa(x) ((unsigned long)(x))
+#define __va(x) ((void *)((unsigned long)(x)))
+
+/*
+ * Special hack: we have to be careful, because no indirections are
+ * allowed here, and paravirt_ops is a kind of one. As it will only run in
+ * baremetal anyway, we just keep it from happening. (This list needs to
+ * be extended when new paravirt and debugging variants are added.)
+ */
+#undef CONFIG_PARAVIRT
+#undef CONFIG_PARAVIRT_SPINLOCKS
+
#include <linux/linkage.h>
#include <linux/init.h>
#include <linux/mm.h>
@@ -489,73 +506,42 @@ static void __init sme_clear_pgd(pgd_t *pgd_base, unsigned long start,
static void __init *sme_populate_pgd(pgd_t *pgd_base, void *pgtable_area,
unsigned long vaddr, pmdval_t pmd_val)
{
- pgd_t *pgd_p;
- p4d_t *p4d_p;
- pud_t *pud_p;
- pmd_t *pmd_p;
-
- pgd_p = pgd_base + pgd_index(vaddr);
- if (native_pgd_val(*pgd_p)) {
- if (IS_ENABLED(CONFIG_X86_5LEVEL))
- p4d_p = (p4d_t *)(native_pgd_val(*pgd_p) & ~PTE_FLAGS_MASK);
- else
- pud_p = (pud_t *)(native_pgd_val(*pgd_p) & ~PTE_FLAGS_MASK);
- } else {
- pgd_t pgd;
-
- if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
- p4d_p = pgtable_area;
- memset(p4d_p, 0, sizeof(*p4d_p) * PTRS_PER_P4D);
- pgtable_area += sizeof(*p4d_p) * PTRS_PER_P4D;
-
- pgd = native_make_pgd((pgdval_t)p4d_p + PGD_FLAGS);
- } else {
- pud_p = pgtable_area;
- memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
- pgtable_area += sizeof(*pud_p) * PTRS_PER_PUD;
-
- pgd = native_make_pgd((pgdval_t)pud_p + PGD_FLAGS);
- }
- native_set_pgd(pgd_p, pgd);
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pgd = pgd_base + pgd_index(vaddr);
+ if (pgd_none(*pgd)) {
+ p4d = pgtable_area;
+ memset(p4d, 0, sizeof(*p4d) * PTRS_PER_P4D);
+ pgtable_area += sizeof(*p4d) * PTRS_PER_P4D;
+ set_pgd(pgd, __pgd(PGD_FLAGS | __pa(p4d)));
}

- if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
- p4d_p += p4d_index(vaddr);
- if (native_p4d_val(*p4d_p)) {
- pud_p = (pud_t *)(native_p4d_val(*p4d_p) & ~PTE_FLAGS_MASK);
- } else {
- p4d_t p4d;
-
- pud_p = pgtable_area;
- memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
- pgtable_area += sizeof(*pud_p) * PTRS_PER_PUD;
-
- p4d = native_make_p4d((pudval_t)pud_p + P4D_FLAGS);
- native_set_p4d(p4d_p, p4d);
- }
+ p4d = p4d_offset(pgd, vaddr);
+ if (p4d_none(*p4d)) {
+ pud = pgtable_area;
+ memset(pud, 0, sizeof(*pud) * PTRS_PER_PUD);
+ pgtable_area += sizeof(*pud) * PTRS_PER_PUD;
+ set_p4d(p4d, __p4d(P4D_FLAGS | __pa(pud)));
}

- pud_p += pud_index(vaddr);
- if (native_pud_val(*pud_p)) {
- if (native_pud_val(*pud_p) & _PAGE_PSE)
- goto out;
-
- pmd_p = (pmd_t *)(native_pud_val(*pud_p) & ~PTE_FLAGS_MASK);
- } else {
- pud_t pud;
-
- pmd_p = pgtable_area;
- memset(pmd_p, 0, sizeof(*pmd_p) * PTRS_PER_PMD);
- pgtable_area += sizeof(*pmd_p) * PTRS_PER_PMD;
-
- pud = native_make_pud((pmdval_t)pmd_p + PUD_FLAGS);
- native_set_pud(pud_p, pud);
+ pud = pud_offset(p4d, vaddr);
+ if (pud_none(*pud)) {
+ pmd = pgtable_area;
+ memset(pmd, 0, sizeof(*pmd) * PTRS_PER_PMD);
+ pgtable_area += sizeof(*pmd) * PTRS_PER_PMD;
+ set_pud(pud, __pud(PUD_FLAGS | __pa(pmd)));
}
+ if (pud_large(*pud))
+ goto out;

- pmd_p += pmd_index(vaddr);
- if (!native_pmd_val(*pmd_p) || !(native_pmd_val(*pmd_p) & _PAGE_PSE))
- native_set_pmd(pmd_p, native_make_pmd(pmd_val));
+ pmd = pmd_offset(pud, vaddr);
+ if (pmd_large(*pmd))
+ goto out;

+ set_pmd(pmd, __pmd(pmd_val));
out:
return pgtable_area;
}
--
Kirill A. Shutemov
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