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Re: [Xen-devel] [PATCH MM-PART2 RESEND v2 04/19] xen/arm: Rework HSCTLR_BASE
Ping, it would be good to know which bits I dropped...
On 21/05/2019 11:09, Julien Grall wrote:
Hi,
On 5/20/19 11:56 PM, Stefano Stabellini wrote:
On Tue, 14 May 2019, Julien Grall wrote:
The current value of HSCTLR_BASE for Arm64 is pretty wrong. It would
actually turn on SCTLR_EL2.nAA (bit 6) on hardware implementing
ARMv8.4-LSE.
Furthermore, the documentation of what is cleared/set in SCTLR_EL2 is
also not correct and looks like to be a verbatim copy from Arm32.
HSCTLR_BASE is replaced with a bunch of per-architecture new defines
helping to understand better what is the initialie value for
s/initialie/initial/
SCTLR_EL2/HSCTLR.
Note the defines *_CLEAR are only used to check the state of each bits
are known.
So basically the only purpose of HSCTLR_CLEAR is to execute:
#if (HSCTLR_SET ^ HSCTLR_CLEAR) != 0xffffffffU
Right? It is good to have the check.
Please add a one-line comment on top of HSCTLR_CLEAR -- "only used to
check that the state of each bits are known".
We don't commonly add a comment every time a define is used only one time. So
what's the benefits here?
In all honesty, such wording in the commit message was probably over the top. I
am thinking to replace the sentence with:
"Lastly, all the bits are now described as either set or cleared. This allows us
to check at pre-processing time the consistency of the initial value."
Lastly, the documentation is dropped from arm{32,64}/head.S as it would
be pretty easy to get out-of-sync with the definitions.
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
Changes in v2:
- Use BIT(..., UL) instead of _BITUL
---
xen/arch/arm/arm32/head.S | 12 +--------
xen/arch/arm/arm64/head.S | 10 +-------
xen/include/asm-arm/processor.h | 54 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 55 insertions(+), 21 deletions(-)
diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 454d24537c..8a98607459 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -234,17 +234,7 @@ cpu_init_done:
ldr r0,
=(TCR_RES1|TCR_SH0_IS|TCR_ORGN0_WBWA|TCR_IRGN0_WBWA|TCR_T0SZ(0))
mcr CP32(r0, HTCR)
- /*
- * Set up the HSCTLR:
- * Exceptions in LE ARM,
- * Low-latency IRQs disabled,
- * Write-implies-XN disabled (for now),
- * D-cache disabled (for now),
- * I-cache enabled,
- * Alignment checking enabled,
- * MMU translation disabled (for now).
- */
- ldr r0, =(HSCTLR_BASE|SCTLR_Axx_ELx_A)
+ ldr r0, =HSCTLR_SET
mcr CP32(r0, HSCTLR)
/*
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 8a6be3352e..4fe904c51d 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -363,15 +363,7 @@ skip_bss:
msr tcr_el2, x0
- /* Set up the SCTLR_EL2:
- * Exceptions in LE ARM,
- * Low-latency IRQs disabled,
- * Write-implies-XN disabled (for now),
- * D-cache disabled (for now),
- * I-cache enabled,
- * Alignment checking disabled,
- * MMU translation disabled (for now). */
- ldr x0, =(HSCTLR_BASE)
+ ldr x0, =SCTLR_EL2_SET
msr SCTLR_EL2, x0
/* Ensure that any exceptions encountered at EL2
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index bbcba061ca..9afc3786c5 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -127,6 +127,9 @@
#define SCTLR_A32_ELx_TE BIT(30, UL)
#define SCTLR_A32_ELx_FI BIT(21, UL)
+/* Common bits for SCTLR_ELx for Arm64 */
+#define SCTLR_A64_ELx_SA BIT(3, UL)
+
/* Common bits for SCTLR_ELx on all architectures */
#define SCTLR_Axx_ELx_EE BIT(25, UL)
#define SCTLR_Axx_ELx_WXN BIT(19, UL)
@@ -135,7 +138,56 @@
#define SCTLR_Axx_ELx_A BIT(1, UL)
#define SCTLR_Axx_ELx_M BIT(0, UL)
-#define HSCTLR_BASE _AC(0x30c51878,U)
+#ifdef CONFIG_ARM_32
+
+#define HSCTLR_RES1 (BIT( 3, UL) | BIT( 4, UL) | BIT( 5, UL) |\
+ BIT( 6, UL) | BIT(11, UL) | BIT(16, UL) |\
+ BIT(18, UL) | BIT(22, UL) | BIT(23, UL) |\
+ BIT(28, UL) | BIT(29, UL))
+
+#define HSCTLR_RES0 (BIT(7, UL) | BIT(8, UL) | BIT(9, UL) | BIT(10,
UL) |\
+ BIT(13, UL) | BIT(14, UL) | BIT(15, UL) | BIT(17,
UL) |\
+ BIT(20, UL) | BIT(24, UL) | BIT(26, UL) | BIT(27,
UL) |\
+ BIT(31, UL))
+
+/* Initial value for HSCTLR */
+#define HSCTLR_SET (HSCTLR_RES1 | SCTLR_Axx_ELx_A | SCTLR_Axx_ELx_I)
As far as my calculations go, it looks like the only difference is
SCTLR_Axx_ELx_A compared to 0x30c51878, right? Which is the alignment
check.
That's correct and match the initial value on Arm32 (see HSCTR_SET |
SCTLR_Axx_ELx_A in the head.S).
+#define HSCTLR_CLEAR (HSCTLR_RES0 | SCTLR_Axx_ELx_M |\
+ SCTLR_Axx_ELx_C | SCTLR_Axx_ELx_WXN |\
+ SCTLR_A32_ELx_FI | SCTLR_Axx_ELx_EE |\
+ SCTLR_A32_ELx_TE)
+
+#if (HSCTLR_SET ^ HSCTLR_CLEAR) != 0xffffffffU
+#error "Inconsistent HSCTLR set/clear bits"
+#endif
+
+#else
+
+#define SCTLR_EL2_RES1 (BIT( 4, UL) | BIT( 5, UL) | BIT(11, UL) |\
+ BIT(16, UL) | BIT(18, UL) | BIT(22, UL) |\
+ BIT(23, UL) | BIT(28, UL) | BIT(29, UL))
+
+#define SCTLR_EL2_RES0 (BIT( 6, UL) | BIT( 7, UL) | BIT( 8, UL) |\
+ BIT( 9, UL) | BIT(10, UL) | BIT(13, UL) |\
+ BIT(14, UL) | BIT(15, UL) | BIT(17, UL) |\
+ BIT(20, UL) | BIT(21, UL) | BIT(24, UL) |\
+ BIT(26, UL) | BIT(27, UL) | BIT(30, UL) |\
+ BIT(31, UL) | (0xffffffffULL << 32))
+
+/* Initial value for SCTLR_EL2 */
+#define SCTLR_EL2_SET (SCTLR_EL2_RES1 | SCTLR_A64_ELx_SA |\
+ SCTLR_Axx_ELx_I)
Same here, you removed the reserved bits, and added the alignment check,
same as for aarch32. If I got it right, it would be nice to add a
statement like this to the commit message.
I don't see why "reserved bits" I dropped nor which alignment check I added.
It would be extremely useful if you provide more details in your review... In
this case, it would be the exact bits I dropped/added.
+#define SCTLR_EL2_CLEAR (SCTLR_EL2_RES0 | SCTLR_Axx_ELx_M |\
+ SCTLR_Axx_ELx_A | SCTLR_Axx_ELx_C |\
+ SCTLR_Axx_ELx_WXN | SCTLR_Axx_ELx_EE)
+
+#if (SCTLR_EL2_SET ^ SCTLR_EL2_CLEAR) != 0xffffffffffffffffUL
+#error "Inconsistent SCTLR_EL2 set/clear bits"
+#endif
+
+#endif
/* HCR Hyp Configuration Register */
#define HCR_RW (_AC(1,UL)<<31) /* Register Width, ARM64 only */
Cheers,
--
Julien Grall
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