lkml.org 
[lkml]   [2017]   [Jun]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v6 30/34] x86/mm, kexec: Allow kexec to be used with SME
On Wed, Jun 07, 2017 at 02:18:27PM -0500, Tom Lendacky wrote:
> Provide support so that kexec can be used to boot a kernel when SME is
> enabled.
>
> Support is needed to allocate pages for kexec without encryption. This
> is needed in order to be able to reboot in the kernel in the same manner
> as originally booted.
>
> Additionally, when shutting down all of the CPUs we need to be sure to
> flush the caches and then halt. This is needed when booting from a state
> where SME was not active into a state where SME is active (or vice-versa).
> Without these steps, it is possible for cache lines to exist for the same
> physical location but tagged both with and without the encryption bit. This
> can cause random memory corruption when caches are flushed depending on
> which cacheline is written last.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> arch/x86/include/asm/init.h | 1 +
> arch/x86/include/asm/kexec.h | 8 ++++++++
> arch/x86/include/asm/pgtable_types.h | 1 +
> arch/x86/kernel/machine_kexec_64.c | 35 +++++++++++++++++++++++++++++++++-
> arch/x86/kernel/process.c | 17 +++++++++++++++--
> arch/x86/mm/ident_map.c | 12 ++++++++----
> include/linux/kexec.h | 14 ++++++++++++++
> kernel/kexec_core.c | 6 ++++++
> 8 files changed, 87 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h
> index 474eb8c..05c4aa0 100644
> --- a/arch/x86/include/asm/init.h
> +++ b/arch/x86/include/asm/init.h
> @@ -7,6 +7,7 @@ struct x86_mapping_info {
> unsigned long page_flag; /* page flag for PMD or PUD entry */
> unsigned long offset; /* ident mapping offset */
> bool direct_gbpages; /* PUD level 1GB page support */
> + unsigned long kernpg_flag; /* kernel pagetable flag override */
> };
>
> int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
> index 70ef205..e8183ac 100644
> --- a/arch/x86/include/asm/kexec.h
> +++ b/arch/x86/include/asm/kexec.h
> @@ -207,6 +207,14 @@ struct kexec_entry64_regs {
> uint64_t r15;
> uint64_t rip;
> };
> +
> +extern int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages,
> + gfp_t gfp);
> +#define arch_kexec_post_alloc_pages arch_kexec_post_alloc_pages
> +
> +extern void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages);
> +#define arch_kexec_pre_free_pages arch_kexec_pre_free_pages
> +
> #endif
>
> typedef void crash_vmclear_fn(void);
> diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
> index ce8cb1c..0f326f4 100644
> --- a/arch/x86/include/asm/pgtable_types.h
> +++ b/arch/x86/include/asm/pgtable_types.h
> @@ -213,6 +213,7 @@ enum page_cache_mode {
> #define PAGE_KERNEL __pgprot(__PAGE_KERNEL | _PAGE_ENC)
> #define PAGE_KERNEL_RO __pgprot(__PAGE_KERNEL_RO | _PAGE_ENC)
> #define PAGE_KERNEL_EXEC __pgprot(__PAGE_KERNEL_EXEC | _PAGE_ENC)
> +#define PAGE_KERNEL_EXEC_NOENC __pgprot(__PAGE_KERNEL_EXEC)
> #define PAGE_KERNEL_RX __pgprot(__PAGE_KERNEL_RX | _PAGE_ENC)
> #define PAGE_KERNEL_NOCACHE __pgprot(__PAGE_KERNEL_NOCACHE | _PAGE_ENC)
> #define PAGE_KERNEL_LARGE __pgprot(__PAGE_KERNEL_LARGE | _PAGE_ENC)
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index 6f5ca4e..35e069a 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -87,7 +87,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
> set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
> }
> pte = pte_offset_kernel(pmd, vaddr);
> - set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC));
> + set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC_NOENC));
> return 0;
> err:
> free_transition_pgtable(image);
> @@ -115,6 +115,7 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
> .alloc_pgt_page = alloc_pgt_page,
> .context = image,
> .page_flag = __PAGE_KERNEL_LARGE_EXEC,
> + .kernpg_flag = _KERNPG_TABLE_NOENC,
> };
> unsigned long mstart, mend;
> pgd_t *level4p;
> @@ -602,3 +603,35 @@ void arch_kexec_unprotect_crashkres(void)
> {
> kexec_mark_crashkres(false);
> }
> +
> +int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, gfp_t gfp)
> +{
> + int ret;
> +
> + if (sme_active()) {

What happened to flipping the logic and saving an indentation level here?

> + /*
> + * If SME is active we need to be sure that kexec pages are
> + * not encrypted because when we boot to the new kernel the
> + * pages won't be accessed encrypted (initially).
> + */
> + ret = set_memory_decrypted((unsigned long)vaddr, pages);
> + if (ret)
> + return ret;
> +
> + if (gfp & __GFP_ZERO)
> + memset(vaddr, 0, pages * PAGE_SIZE);
> + }

This is still zeroing the memory a second time. That function has missed
all my comments from last time.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

\
 
 \ /
  Last update: 2017-06-15 12:05    [W:0.409 / U:2.868 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site