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SubjectRe: [PATCH, RFC 18/62] x86/mm: Implement syncing per-KeyID direct mappings
On Mon, Jun 17, 2019 at 11:27:55AM +0200, Peter Zijlstra wrote:
> On Sat, Jun 15, 2019 at 01:43:09AM +0300, Kirill A. Shutemov wrote:
> > On Fri, Jun 14, 2019 at 11:51:32AM +0200, Peter Zijlstra wrote:
> > > On Wed, May 08, 2019 at 05:43:38PM +0300, Kirill A. Shutemov wrote:
> > > > For MKTME we use per-KeyID direct mappings. This allows kernel to have
> > > > access to encrypted memory.
> > > >
> > > > sync_direct_mapping() sync per-KeyID direct mappings with a canonical
> > > > one -- KeyID-0.
> > > >
> > > > The function tracks changes in the canonical mapping:
> > > > - creating or removing chunks of the translation tree;
> > > > - changes in mapping flags (i.e. protection bits);
> > > > - splitting huge page mapping into a page table;
> > > > - replacing page table with a huge page mapping;
> > > >
> > > > The function need to be called on every change to the direct mapping:
> > > > hotplug, hotremove, changes in permissions bits, etc.
> > >
> > > And yet I don't see anything in pageattr.c.
> >
> > You're right. I've hooked up the sync in the wrong place.
> > >
> > > Also, this seems like an expensive scheme; if you know where the changes
> > > where, a more fine-grained update would be faster.
> >
> > Do we have any hot enough pageattr users that makes it crucial?
> >
> > I'll look into this anyway.
>
> The graphics people would be the most agressive users of this I'd think.
> They're the ones that yelled when I broke it last ;-)

I think something like this should do (I'll fold it in after testing):

diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
index 6c973cb1e64c..b30386d84281 100644
--- a/arch/x86/include/asm/mktme.h
+++ b/arch/x86/include/asm/mktme.h
@@ -68,7 +68,7 @@ static inline void arch_free_page(struct page *page, int order)
free_encrypted_page(page, order);
}

-int sync_direct_mapping(void);
+int sync_direct_mapping(unsigned long start, unsigned long end);

int mktme_get_alg(int keyid);

@@ -86,7 +86,7 @@ static inline bool mktme_enabled(void)

static inline void mktme_disable(void) {}

-static inline int sync_direct_mapping(void)
+static inline int sync_direct_mapping(unsigned long start, unsigned long end)
{
return 0;
}
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index f50a38d86cc4..f8123aeb24a6 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -761,7 +761,7 @@ __kernel_physical_mapping_init(unsigned long paddr_start,
pgd_changed = true;
}

- ret = sync_direct_mapping();
+ ret = sync_direct_mapping(vaddr_start, vaddr_end);
WARN_ON(ret);

if (pgd_changed)
@@ -1209,7 +1209,7 @@ kernel_physical_mapping_remove(unsigned long start, unsigned long end)
end = (unsigned long)__va(end);

remove_pagetable(start, end, true, NULL);
- ret = sync_direct_mapping();
+ ret = sync_direct_mapping(start, end);
WARN_ON(ret);
}

@@ -1315,7 +1315,6 @@ void mark_rodata_ro(void)
unsigned long text_end = PFN_ALIGN(&__stop___ex_table);
unsigned long rodata_end = PFN_ALIGN(&__end_rodata);
unsigned long all_end;
- int ret;

printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
(end - start) >> 10);
@@ -1349,8 +1348,6 @@ void mark_rodata_ro(void)
free_kernel_image_pages((void *)text_end, (void *)rodata_start);
free_kernel_image_pages((void *)rodata_end, (void *)_sdata);

- ret = sync_direct_mapping();
- WARN_ON(ret);
debug_checkwx();
}

diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c
index 9d2bb534f2ba..c099e1da055b 100644
--- a/arch/x86/mm/mktme.c
+++ b/arch/x86/mm/mktme.c
@@ -76,7 +76,7 @@ static void init_page_mktme(void)
{
static_branch_enable(&mktme_enabled_key);

- sync_direct_mapping();
+ sync_direct_mapping(PAGE_OFFSET, PAGE_OFFSET + direct_mapping_size);
}

struct page_ext_operations page_mktme_ops = {
@@ -596,15 +596,13 @@ static int sync_direct_mapping_p4d(unsigned long keyid,
return ret;
}

-static int sync_direct_mapping_keyid(unsigned long keyid)
+static int sync_direct_mapping_keyid(unsigned long keyid,
+ unsigned long addr, unsigned long end)
{
pgd_t *src_pgd, *dst_pgd;
- unsigned long addr, end, next;
+ unsigned long next;
int ret = 0;

- addr = PAGE_OFFSET;
- end = PAGE_OFFSET + direct_mapping_size;
-
dst_pgd = pgd_offset_k(addr + keyid * direct_mapping_size);
src_pgd = pgd_offset_k(addr);

@@ -643,7 +641,7 @@ static int sync_direct_mapping_keyid(unsigned long keyid)
*
* The function is nop until MKTME is enabled.
*/
-int sync_direct_mapping(void)
+int sync_direct_mapping(unsigned long start, unsigned long end)
{
int i, ret = 0;

@@ -651,7 +649,7 @@ int sync_direct_mapping(void)
return 0;

for (i = 1; !ret && i <= mktme_nr_keyids; i++)
- ret = sync_direct_mapping_keyid(i);
+ ret = sync_direct_mapping_keyid(i, start, end);

flush_tlb_all();

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 6a9a77a403c9..eafbe0d8c44f 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -347,6 +347,28 @@ static void cpa_flush(struct cpa_data *data, int cache)

BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);

+ if (mktme_enabled()) {
+ unsigned long start, end;
+
+ start = *cpa->vaddr;
+ end = *cpa->vaddr + cpa->numpages * PAGE_SIZE;
+
+ /* Sync all direct mapping for an array */
+ if (cpa->flags & CPA_ARRAY) {
+ start = PAGE_OFFSET;
+ end = PAGE_OFFSET + direct_mapping_size;
+ }
+
+ /*
+ * Sync per-KeyID direct mappings with the canonical one
+ * (KeyID-0).
+ *
+ * sync_direct_mapping() does full TLB flush.
+ */
+ sync_direct_mapping(start, end);
+ return;
+ }
+
if (cache && !static_cpu_has(X86_FEATURE_CLFLUSH)) {
cpa_flush_all(cache);
return;
--
Kirill A. Shutemov
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