* [PATCH] ARM, arm64: kvm: get rid of the bounce page
@ 2015-03-27 10:18 Ard Biesheuvel
2015-03-27 10:18 ` [PATCH] ARM: kvm: round HYP section to page size instead of log2 upper bound Ard Biesheuvel
0 siblings, 1 reply; 5+ messages in thread
From: Ard Biesheuvel @ 2015-03-27 10:18 UTC (permalink / raw)
To: linux-arm-kernel
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 both ARM and arm64, we just align to 4 KB, and enforce that the code
size is less than 4 KB, regardless of the chosen page 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.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm/kernel/vmlinux.lds.S | 11 +++++++----
arch/arm/kvm/mmu.c | 42 +++++------------------------------------
arch/arm64/kernel/vmlinux.lds.S | 17 +++++++++++------
3 files changed, 23 insertions(+), 47 deletions(-)
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index b31aa73e8076..f2db429ea75d 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -23,7 +23,7 @@
VMLINUX_SYMBOL(__idmap_text_start) = .; \
*(.idmap.text) \
VMLINUX_SYMBOL(__idmap_text_end) = .; \
- . = ALIGN(32); \
+ . = ALIGN(PAGE_SIZE); \
VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
*(.hyp.idmap.text) \
VMLINUX_SYMBOL(__hyp_idmap_text_end) = .;
@@ -346,8 +346,11 @@ 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 - (__hyp_idmap_text_start & PAGE_MASK) <= PAGE_SIZE,
+ "HYP init code too big or misaligned")
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..a2c29865c3fe 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@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 +167,11 @@ 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 - (__hyp_idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K,
+ "HYP init code too big or misaligned")
/*
* If padding is applied before .head.text, virt<->phys conversions will fail.
--
1.8.3.2
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH] ARM: kvm: round HYP section to page size instead of log2 upper bound
2015-03-27 10:18 [PATCH] ARM, arm64: kvm: get rid of the bounce page Ard Biesheuvel
@ 2015-03-27 10:18 ` Ard Biesheuvel
2015-03-27 11:09 ` Will Deacon
0 siblings, 1 reply; 5+ messages in thread
From: Ard Biesheuvel @ 2015-03-27 10:18 UTC (permalink / raw)
To: linux-arm-kernel
Older binutils do not support expressions involving the values of
external symbols so just round up the HYP region to the page size.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm/kernel/vmlinux.lds.S | 31 +------------------------------
arch/arm/kvm/init.S | 3 ---
2 files changed, 1 insertion(+), 33 deletions(-)
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 808398ec024e..f2db429ea75d 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -12,26 +12,6 @@
#include <asm/pgtable.h>
#endif
-/*
- * Poor man's version of LOG2CEIL(), which is
- * not available in binutils before v2.24.
- */
-#define LOG2_ROUNDUP(size) ( \
- __LOG2_ROUNDUP(size, 2) \
- __LOG2_ROUNDUP(size, 3) \
- __LOG2_ROUNDUP(size, 4) \
- __LOG2_ROUNDUP(size, 5) \
- __LOG2_ROUNDUP(size, 6) \
- __LOG2_ROUNDUP(size, 7) \
- __LOG2_ROUNDUP(size, 8) \
- __LOG2_ROUNDUP(size, 9) \
- __LOG2_ROUNDUP(size, 10) \
- __LOG2_ROUNDUP(size, 11) \
- 12)
-
-#define __LOG2_ROUNDUP(size, order) \
- (size) <= (1 << order) ? order :
-
#define PROC_INFO \
. = ALIGN(4); \
VMLINUX_SYMBOL(__proc_info_begin) = .; \
@@ -43,20 +23,11 @@
VMLINUX_SYMBOL(__idmap_text_start) = .; \
*(.idmap.text) \
VMLINUX_SYMBOL(__idmap_text_end) = .; \
- . = ALIGN(1 << LOG2_ROUNDUP(__hyp_idmap_size)); \
+ . = ALIGN(PAGE_SIZE); \
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);
-
#ifdef CONFIG_HOTPLUG_CPU
#define ARM_CPU_DISCARD(x)
#define ARM_CPU_KEEP(x) x
diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
index 11fb1d56f449..3988e72d16ff 100644
--- a/arch/arm/kvm/init.S
+++ b/arch/arm/kvm/init.S
@@ -157,6 +157,3 @@ 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
--
1.8.3.2
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH] ARM: kvm: round HYP section to page size instead of log2 upper bound
2015-03-27 10:18 ` [PATCH] ARM: kvm: round HYP section to page size instead of log2 upper bound Ard Biesheuvel
@ 2015-03-27 11:09 ` Will Deacon
2015-03-27 11:12 ` Ard Biesheuvel
0 siblings, 1 reply; 5+ messages in thread
From: Will Deacon @ 2015-03-27 11:09 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, Mar 27, 2015 at 10:18:01AM +0000, Ard Biesheuvel wrote:
> Older binutils do not support expressions involving the values of
> external symbols so just round up the HYP region to the page size.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Thanks Ard. I managed to reproduce the failures in -next, and this solves
the problem for me (the only toolchain that chokes seems to be the one on
kernel.org, unfortunately).
I'll push an updated branch after a bit more testing. Let's not touch this
file ever again :)
Will
> ---
> arch/arm/kernel/vmlinux.lds.S | 31 +------------------------------
> arch/arm/kvm/init.S | 3 ---
> 2 files changed, 1 insertion(+), 33 deletions(-)
>
> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
> index 808398ec024e..f2db429ea75d 100644
> --- a/arch/arm/kernel/vmlinux.lds.S
> +++ b/arch/arm/kernel/vmlinux.lds.S
> @@ -12,26 +12,6 @@
> #include <asm/pgtable.h>
> #endif
>
> -/*
> - * Poor man's version of LOG2CEIL(), which is
> - * not available in binutils before v2.24.
> - */
> -#define LOG2_ROUNDUP(size) ( \
> - __LOG2_ROUNDUP(size, 2) \
> - __LOG2_ROUNDUP(size, 3) \
> - __LOG2_ROUNDUP(size, 4) \
> - __LOG2_ROUNDUP(size, 5) \
> - __LOG2_ROUNDUP(size, 6) \
> - __LOG2_ROUNDUP(size, 7) \
> - __LOG2_ROUNDUP(size, 8) \
> - __LOG2_ROUNDUP(size, 9) \
> - __LOG2_ROUNDUP(size, 10) \
> - __LOG2_ROUNDUP(size, 11) \
> - 12)
> -
> -#define __LOG2_ROUNDUP(size, order) \
> - (size) <= (1 << order) ? order :
> -
> #define PROC_INFO \
> . = ALIGN(4); \
> VMLINUX_SYMBOL(__proc_info_begin) = .; \
> @@ -43,20 +23,11 @@
> VMLINUX_SYMBOL(__idmap_text_start) = .; \
> *(.idmap.text) \
> VMLINUX_SYMBOL(__idmap_text_end) = .; \
> - . = ALIGN(1 << LOG2_ROUNDUP(__hyp_idmap_size)); \
> + . = ALIGN(PAGE_SIZE); \
> 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);
> -
> #ifdef CONFIG_HOTPLUG_CPU
> #define ARM_CPU_DISCARD(x)
> #define ARM_CPU_KEEP(x) x
> diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
> index 11fb1d56f449..3988e72d16ff 100644
> --- a/arch/arm/kvm/init.S
> +++ b/arch/arm/kvm/init.S
> @@ -157,6 +157,3 @@ 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
> --
> 1.8.3.2
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] ARM: kvm: round HYP section to page size instead of log2 upper bound
2015-03-27 11:09 ` Will Deacon
@ 2015-03-27 11:12 ` Ard Biesheuvel
2015-03-27 12:13 ` Simon Horman
0 siblings, 1 reply; 5+ messages in thread
From: Ard Biesheuvel @ 2015-03-27 11:12 UTC (permalink / raw)
To: linux-arm-kernel
On 27 March 2015 at 12:09, Will Deacon <will.deacon@arm.com> wrote:
> On Fri, Mar 27, 2015 at 10:18:01AM +0000, Ard Biesheuvel wrote:
>> Older binutils do not support expressions involving the values of
>> external symbols so just round up the HYP region to the page size.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>
> Thanks Ard. I managed to reproduce the failures in -next, and this solves
> the problem for me (the only toolchain that chokes seems to be the one on
> kernel.org, unfortunately).
>
> I'll push an updated branch after a bit more testing. Let's not touch this
> file ever again :)
>
Fingers crossed ...
>> ---
>> arch/arm/kernel/vmlinux.lds.S | 31 +------------------------------
>> arch/arm/kvm/init.S | 3 ---
>> 2 files changed, 1 insertion(+), 33 deletions(-)
>>
>> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
>> index 808398ec024e..f2db429ea75d 100644
>> --- a/arch/arm/kernel/vmlinux.lds.S
>> +++ b/arch/arm/kernel/vmlinux.lds.S
>> @@ -12,26 +12,6 @@
>> #include <asm/pgtable.h>
>> #endif
>>
>> -/*
>> - * Poor man's version of LOG2CEIL(), which is
>> - * not available in binutils before v2.24.
>> - */
>> -#define LOG2_ROUNDUP(size) ( \
>> - __LOG2_ROUNDUP(size, 2) \
>> - __LOG2_ROUNDUP(size, 3) \
>> - __LOG2_ROUNDUP(size, 4) \
>> - __LOG2_ROUNDUP(size, 5) \
>> - __LOG2_ROUNDUP(size, 6) \
>> - __LOG2_ROUNDUP(size, 7) \
>> - __LOG2_ROUNDUP(size, 8) \
>> - __LOG2_ROUNDUP(size, 9) \
>> - __LOG2_ROUNDUP(size, 10) \
>> - __LOG2_ROUNDUP(size, 11) \
>> - 12)
>> -
>> -#define __LOG2_ROUNDUP(size, order) \
>> - (size) <= (1 << order) ? order :
>> -
>> #define PROC_INFO \
>> . = ALIGN(4); \
>> VMLINUX_SYMBOL(__proc_info_begin) = .; \
>> @@ -43,20 +23,11 @@
>> VMLINUX_SYMBOL(__idmap_text_start) = .; \
>> *(.idmap.text) \
>> VMLINUX_SYMBOL(__idmap_text_end) = .; \
>> - . = ALIGN(1 << LOG2_ROUNDUP(__hyp_idmap_size)); \
>> + . = ALIGN(PAGE_SIZE); \
>> 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);
>> -
>> #ifdef CONFIG_HOTPLUG_CPU
>> #define ARM_CPU_DISCARD(x)
>> #define ARM_CPU_KEEP(x) x
>> diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
>> index 11fb1d56f449..3988e72d16ff 100644
>> --- a/arch/arm/kvm/init.S
>> +++ b/arch/arm/kvm/init.S
>> @@ -157,6 +157,3 @@ 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
>> --
>> 1.8.3.2
>>
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] ARM: kvm: round HYP section to page size instead of log2 upper bound
2015-03-27 11:12 ` Ard Biesheuvel
@ 2015-03-27 12:13 ` Simon Horman
0 siblings, 0 replies; 5+ messages in thread
From: Simon Horman @ 2015-03-27 12:13 UTC (permalink / raw)
To: linux-arm-kernel
Hi Ard, Hi Will,
On Fri, Mar 27, 2015 at 12:12:00PM +0100, Ard Biesheuvel wrote:
> On 27 March 2015 at 12:09, Will Deacon <will.deacon@arm.com> wrote:
> > On Fri, Mar 27, 2015 at 10:18:01AM +0000, Ard Biesheuvel wrote:
> >> Older binutils do not support expressions involving the values of
> >> external symbols so just round up the HYP region to the page size.
> >>
> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >
> > Thanks Ard. I managed to reproduce the failures in -next, and this solves
> > the problem for me (the only toolchain that chokes seems to be the one on
> > kernel.org, unfortunately).
For the record that is the one I am using.
> > I'll push an updated branch after a bit more testing. Let's not touch this
> > file ever again :)
:)
> Fingers crossed ...
I have tested this patch applied on top of next-20150326 and the build
problem I observed is gone. I have also tested that the resulting kernel
boots on a range of Renesas boards.
Tested-by: Simon Horman <horms+renesas@verge.net.au>
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2015-03-27 12:13 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2015-03-27 10:18 [PATCH] ARM, arm64: kvm: get rid of the bounce page Ard Biesheuvel
2015-03-27 10:18 ` [PATCH] ARM: kvm: round HYP section to page size instead of log2 upper bound Ard Biesheuvel
2015-03-27 11:09 ` Will Deacon
2015-03-27 11:12 ` Ard Biesheuvel
2015-03-27 12:13 ` Simon Horman
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