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Date: Tue, 30 Jan 2018 16:48:17 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Borislav Petkov <bp@...e.de>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 2/3] x86/mm/encrypt: Rewrite sme_populate_pgd() and
sme_populate_pgd_large()
On 1/24/2018 10:36 AM, Kirill A. Shutemov wrote:
> sme_populate_pgd() and sme_populate_pgd_large() operate on the identity
> mapping, which means they want virtual addresses to be equal to physical
> one, without PAGE_OFFSET shift.
>
> We also need to avoid paravirtualizaion call there.
paravirtualization
>
> Getting this done is tricky. We cannot use usual page table helpers.
> It forces us to open-code a lot of things. It makes code ugly and hard
> to modify.
>
> We can get it work with the page table helpers, but it requires few
> preprocessor tricks.
>
> - Define __pa() and __va() to be compatible with identity mapping.
>
> - Undef CONFIG_PARAVIRT and CONFIG_PARAVIRT_SPINLOCKS before including
> any file. This way we can avoid pearavirtualization calls.
paravirtualization
>
> Now we can user normal page table helpers just fine.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> ---
> arch/x86/mm/mem_encrypt_identity.c | 159 +++++++++++++++++--------------------
> 1 file changed, 72 insertions(+), 87 deletions(-)
>
> diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
> index c23d55cb25c4..69635a02ce9e 100644
> --- a/arch/x86/mm/mem_encrypt_identity.c
> +++ b/arch/x86/mm/mem_encrypt_identity.c
> @@ -12,6 +12,24 @@
>
> #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/kernel.h>
> #include <linux/mm.h>
>
> #include <asm/setup.h>
> @@ -72,116 +90,83 @@ static void __init sme_clear_pgd(struct sme_populate_pgd_data *ppd)
> memset(pgd_p, 0, pgd_size);
> }
>
> -static pmd_t __init *sme_prepare_pgd(struct sme_populate_pgd_data *ppd)
> +static pud_t __init *sme_prepare_pgd(struct sme_populate_pgd_data *ppd)
> {
> - pgd_t *pgd_p;
> - p4d_t *p4d_p;
> - pud_t *pud_p;
> - pmd_t *pmd_p;
> -
> - pgd_p = ppd->pgd + pgd_index(ppd->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 = ppd->pgtable_area;
> - memset(p4d_p, 0, sizeof(*p4d_p) * PTRS_PER_P4D);
> - ppd->pgtable_area += sizeof(*p4d_p) * PTRS_PER_P4D;
> -
> - pgd = native_make_pgd((pgdval_t)p4d_p + PGD_FLAGS);
> - } else {
> - pud_p = ppd->pgtable_area;
> - memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
> - ppd->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 = ppd->pgd + pgd_index(ppd->vaddr);
> + if (pgd_none(*pgd)) {
> + p4d = ppd->pgtable_area;
> + memset(p4d, 0, sizeof(*p4d) * PTRS_PER_P4D);
> + ppd->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(ppd->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 = ppd->pgtable_area;
> - memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
> - ppd->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, ppd->vaddr);
> + if (p4d_none(*p4d)) {
> + pud = ppd->pgtable_area;
> + memset(pud, 0, sizeof(*pud) * PTRS_PER_PUD);
> + ppd->pgtable_area += sizeof(*pud) * PTRS_PER_PUD;
> + set_p4d(p4d, __p4d(P4D_FLAGS | __pa(pud)));
> }
>
> - pud_p += pud_index(ppd->vaddr);
> - if (native_pud_val(*pud_p)) {
> - if (native_pud_val(*pud_p) & _PAGE_PSE)
> - return NULL;
> -
> - pmd_p = (pmd_t *)(native_pud_val(*pud_p) & ~PTE_FLAGS_MASK);
> - } else {
> - pud_t pud;
> -
> - pmd_p = ppd->pgtable_area;
> - memset(pmd_p, 0, sizeof(*pmd_p) * PTRS_PER_PMD);
> - ppd->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, ppd->vaddr);
> + if (pud_none(*pud)) {
> + pmd = ppd->pgtable_area;
> + memset(pmd, 0, sizeof(*pmd) * PTRS_PER_PMD);
> + ppd->pgtable_area += sizeof(*pmd) * PTRS_PER_PMD;
> + set_pud(pud, __pud(PUD_FLAGS | __pa(pmd)));
> }
>
> - return pmd_p;
> + if (pud_large(*pud))
> + return NULL;
> +
> + return pud;
> }
>
> static void __init sme_populate_pgd_large(struct sme_populate_pgd_data *ppd)
> {
> - pmd_t *pmd_p;
> + pud_t *pud;
> + pmd_t *pmd;
>
> - pmd_p = sme_prepare_pgd(ppd);
> - if (!pmd_p)
> + pud = sme_prepare_pgd(ppd);
> + if (!pud)
> return;
>
> - pmd_p += pmd_index(ppd->vaddr);
> - if (!native_pmd_val(*pmd_p) || !(native_pmd_val(*pmd_p) & _PAGE_PSE))
> - native_set_pmd(pmd_p, native_make_pmd(ppd->paddr | ppd->pmd_flags));
> + pmd = pmd_offset(pud, ppd->vaddr);
> + if (pmd_large(*pmd))
> + return;
> +
> + set_pmd(pmd, __pmd(ppd->paddr | ppd->pmd_flags));
> }
>
> static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd)
> {
> - pmd_t *pmd_p;
> - pte_t *pte_p;
> + pud_t *pud;
> + pmd_t *pmd;
> + pte_t *pte;
>
> - pmd_p = sme_prepare_pgd(ppd);
> - if (!pmd_p)
> + pud = sme_prepare_pgd(ppd);
> + if (!pud)
> return;
>
> - pmd_p += pmd_index(ppd->vaddr);
> - if (native_pmd_val(*pmd_p)) {
> - if (native_pmd_val(*pmd_p) & _PAGE_PSE)
> - return;
> -
> - pte_p = (pte_t *)(native_pmd_val(*pmd_p) & ~PTE_FLAGS_MASK);
> - } else {
> - pmd_t pmd;
> -
> - pte_p = ppd->pgtable_area;
> - memset(pte_p, 0, sizeof(*pte_p) * PTRS_PER_PTE);
> - ppd->pgtable_area += sizeof(*pte_p) * PTRS_PER_PTE;
> -
> - pmd = native_make_pmd((pteval_t)pte_p + PMD_FLAGS);
> - native_set_pmd(pmd_p, pmd);
> + pmd = pmd_offset(pud, ppd->vaddr);
> + if (pmd_none(*pmd)) {
> + pte = ppd->pgtable_area;
> + memset(pte, 0, sizeof(pte) * PTRS_PER_PTE);
> + ppd->pgtable_area += sizeof(pte) * PTRS_PER_PTE;
> + set_pmd(pmd, __pmd(PMD_FLAGS | __pa(pte)));
> }
>
> - pte_p += pte_index(ppd->vaddr);
> - if (!native_pte_val(*pte_p))
> - native_set_pte(pte_p, native_make_pte(ppd->paddr | ppd->pte_flags));
> + if (pmd_large(*pmd))
> + return;
> +
> + pte = pte_offset_map(pmd, ppd->vaddr);
> + if (pte_none(*pte))
> + set_pte(pte, __pte(ppd->paddr | ppd->pte_flags));
> }
>
> static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd)
>
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