ARM, arm64: kvm: get rid of the bounce page
The HYP init bounce page is a runtime construct that ensures that the
HYP init code does not cross a page boundary. However, this is something
we can do perfectly well at build time, by aligning the code appropriately.
For arm64, we just align to 4 KB, and enforce that the code size is less
than 4 KB, regardless of the chosen page size.
For ARM, the whole code is less than 256 bytes, so we tweak the linker
script to align at a power of 2 upper bound of the code size
Note that this also fixes a benign off-by-one error in the original bounce
page code, where a bounce page would be allocated unnecessarily if the code
was exactly 1 page in size.
On ARM, it also fixes an issue with very large kernels reported by Arnd
Bergmann, where stub sections with linker emitted veneers could erroneously
trigger the size/alignment ASSERT() in the linker script.
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 3e6859b..42a24d6 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -37,7 +37,6 @@
static pgd_t *hyp_pgd;
static DEFINE_MUTEX(kvm_hyp_pgd_mutex);
-static void *init_bounce_page;
static unsigned long hyp_idmap_start;
static unsigned long hyp_idmap_end;
static phys_addr_t hyp_idmap_vector;
@@ -405,9 +404,6 @@
if (hyp_pgd)
unmap_range(NULL, hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
- free_page((unsigned long)init_bounce_page);
- init_bounce_page = NULL;
-
mutex_unlock(&kvm_hyp_pgd_mutex);
}
@@ -1498,39 +1494,11 @@
hyp_idmap_end = kvm_virt_to_phys(__hyp_idmap_text_end);
hyp_idmap_vector = kvm_virt_to_phys(__kvm_hyp_init);
- if ((hyp_idmap_start ^ hyp_idmap_end) & PAGE_MASK) {
- /*
- * Our init code is crossing a page boundary. Allocate
- * a bounce page, copy the code over and use that.
- */
- size_t len = __hyp_idmap_text_end - __hyp_idmap_text_start;
- phys_addr_t phys_base;
-
- init_bounce_page = (void *)__get_free_page(GFP_KERNEL);
- if (!init_bounce_page) {
- kvm_err("Couldn't allocate HYP init bounce page\n");
- err = -ENOMEM;
- goto out;
- }
-
- memcpy(init_bounce_page, __hyp_idmap_text_start, len);
- /*
- * Warning: the code we just copied to the bounce page
- * must be flushed to the point of coherency.
- * Otherwise, the data may be sitting in L2, and HYP
- * mode won't be able to observe it as it runs with
- * caches off at that point.
- */
- kvm_flush_dcache_to_poc(init_bounce_page, len);
-
- phys_base = kvm_virt_to_phys(init_bounce_page);
- hyp_idmap_vector += phys_base - hyp_idmap_start;
- hyp_idmap_start = phys_base;
- hyp_idmap_end = phys_base + len;
-
- kvm_info("Using HYP init bounce page @%lx\n",
- (unsigned long)phys_base);
- }
+ /*
+ * We rely on the linker script to ensure at build time that the HYP
+ * init code does not cross a page boundary.
+ */
+ BUG_ON((hyp_idmap_start ^ (hyp_idmap_end - 1)) & PAGE_MASK);
hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, hyp_pgd_order);
boot_hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, hyp_pgd_order);