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.
Tested-by: Marc Zyngier <marc.zyng...@arm.com>
Reviewed-by: Marc Zyngier <marc.zyng...@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
---
arch/arm/kernel/vmlinux.lds.S | 26 ++++++++++++++++++++++---
arch/arm/kvm/init.S | 3 +++
arch/arm/kvm/mmu.c | 42 +++++------------------------------------
arch/arm64/kernel/vmlinux.lds.S | 18 ++++++++++++------
4 files changed, 43 insertions(+), 46 deletions(-)
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 2787eb8d3616..85db1669bfe3 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -26,12 +26,28 @@
#define IDMAP_RODATA \
.rodata : { \
- . = ALIGN(32); \
+ . = ALIGN(HYP_IDMAP_ALIGN); \
VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
*(.hyp.idmap.text) \
VMLINUX_SYMBOL(__hyp_idmap_text_end) = .; \
}
+/*
+ * If the HYP idmap .text section is populated, it needs to be positioned
+ * such that it will not cross a page boundary in the final output image.
+ * So align it to the section size rounded up to the next power of 2.
+ * If __hyp_idmap_size is undefined, the section will be empty so define
+ * it as 0 in that case.
+ */
+PROVIDE(__hyp_idmap_size = 0);
+
+#define HYP_IDMAP_ALIGN
\
+ __hyp_idmap_size == 0 ? 0 : \
+ __hyp_idmap_size <= 0x100 ? 0x100 : \
+ __hyp_idmap_size <= 0x200 ? 0x200 : \
+ __hyp_idmap_size <= 0x400 ? 0x400 : \
+ __hyp_idmap_size <= 0x800 ? 0x800 : 0x1000
+
#ifdef CONFIG_HOTPLUG_CPU
#define ARM_CPU_DISCARD(x)
#define ARM_CPU_KEEP(x) x
@@ -351,8 +367,12 @@ SECTIONS
*/
ASSERT((__proc_info_end - __proc_info_begin), "missing CPU support")
ASSERT((__arch_info_end - __arch_info_begin), "no machine record defined")
+
/*
- * The HYP init code can't be more than a page long.
+ * The HYP init code can't be more than a page long,
+ * and should not cross a page boundary.
* The above comment applies as well.
*/
-ASSERT(((__hyp_idmap_text_end - __hyp_idmap_text_start) <= PAGE_SIZE), "HYP
init code too big")
+ASSERT(((__hyp_idmap_text_end - 1) & PAGE_MASK) -
+ (__hyp_idmap_text_start & PAGE_MASK) == 0,
+ "HYP init code too big or unaligned")
diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
index 3988e72d16ff..11fb1d56f449 100644
--- a/arch/arm/kvm/init.S
+++ b/arch/arm/kvm/init.S
@@ -157,3 +157,6 @@ target: @ We're now in the trampoline code, switch page
tables
__kvm_hyp_init_end:
.popsection
+
+ .global __hyp_idmap_size
+ .set __hyp_idmap_size, __kvm_hyp_init_end - __kvm_hyp_init
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 3e6859bc3e11..42a24d6b003b 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -37,7 +37,6 @@ static pgd_t *boot_hyp_pgd;
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 @@ void free_boot_hyp_pgd(void)
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 @@ int kvm_mmu_init(void)
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);
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 5d9d2dca530d..9e447f983fae 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -23,10 +23,14 @@ jiffies = jiffies_64;
#define HYPERVISOR_TEXT \
/* \
- * Force the alignment to be compatible with \
- * the vectors requirements \
+ * Align to 4 KB so that \
+ * a) the HYP vector table is at its minimum \
+ * alignment of 2048 bytes \
+ * b) the HYP init code will not cross a page \
+ * boundary if its size does not exceed \
+ * 4 KB (see related ASSERT() below) \
*/ \
- . = ALIGN(2048); \
+ . = ALIGN(SZ_4K); \
VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
*(.hyp.idmap.text) \
VMLINUX_SYMBOL(__hyp_idmap_text_end) = .; \
@@ -163,10 +167,12 @@ SECTIONS
}
/*
- * The HYP init code can't be more than a page long.
+ * The HYP init code can't be more than a page long,
+ * and should not cross a page boundary.
*/
-ASSERT(((__hyp_idmap_text_start + PAGE_SIZE) > __hyp_idmap_text_end),
- "HYP init code too big")
+ASSERT(((__hyp_idmap_text_end - 1) & ~(SZ_4K - 1)) -
+ (__hyp_idmap_text_start & ~(SZ_4K - 1)) == 0,
+ "HYP init code too big or unaligned")
/*
* If padding is applied before .head.text, virt<->phys conversions will fail.
--
1.8.3.2
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