Hello Julien,
On 17.04.19 20:58, Julien Grall wrote:
The function flush_xen_text_tlb_local() has been misused and will result
to invalidate the instruction cache more than necessary.
For instance, there are no need to invalidate the instruction cache if
we are setting SCTLR_EL2.WXN.
There are effectively only one caller (i.e free_init_memory() would
who need to invalidate the instruction cache.
So rather than keeping around the function flush_xen_text_tlb_local()
around, replace it with call to flush_xen_tlb_local() and explicitely
flush the cache when necessary.
Signed-off-by: Julien Grall <julien.gr...@arm.com>
---
xen/arch/arm/mm.c | 17 ++++++++++++++---
xen/include/asm-arm/arm32/page.h | 23 +++++++++--------------
xen/include/asm-arm/arm64/page.h | 21 +++++----------------
3 files changed, 28 insertions(+), 33 deletions(-)
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 93ad118183..dfbe39c70a 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -610,8 +610,12 @@ void __init remove_early_mappings(void)
static void xen_pt_enforce_wnx(void)
{
WRITE_SYSREG32(READ_SYSREG32(SCTLR_EL2) | SCTLR_WXN, SCTLR_EL2);
- /* Flush everything after setting WXN bit. */
- flush_xen_text_tlb_local();
+ /*
+ * The TLBs may cache SCTLR_EL2.WXN. So ensure it is synchronized
+ * before flushing the TLBs.
I'm not sure about the comment above, it looks a bit confusing to me.
As per my understanding flushing TLB is called to remove cached entries
together with cached SCTLR_EL2.WXN.
And isb before to tlb flush ensures that WXN is set prior to flush so that all
new TLB entries will be fetched
with this flag set.
+ */
+ isb();
+ flush_xen_data_tlb_local();
}
extern void switch_ttbr(uint64_t ttbr);
@@ -1123,7 +1127,7 @@ static void set_pte_flags_on_range(const char *p,
unsigned long l, enum mg mg)
}
write_pte(xen_xenmap + i, pte);
}
- flush_xen_text_tlb_local();
+ flush_xen_data_tlb_local();
}
/* Release all __init and __initdata ranges to be reused */
@@ -1136,6 +1140,13 @@ void free_init_memory(void)
uint32_t *p;
set_pte_flags_on_range(__init_begin, len, mg_rw);
+
+ /*
+ * From now on, init will not be used for execution anymore,
+ * so nuke the instruction cache to remove entries related to init.
+ */
+ invalidate_icache_local();
+
#ifdef CONFIG_ARM_32
/* udf instruction i.e (see A8.8.247 in ARM DDI 0406C.c) */
insn = 0xe7f000f0;
diff --git a/xen/include/asm-arm/arm32/page.h b/xen/include/asm-arm/arm32/page.h
index ea4b312c70..40a77daa9d 100644
--- a/xen/include/asm-arm/arm32/page.h
+++ b/xen/include/asm-arm/arm32/page.h
@@ -46,24 +46,19 @@ static inline void invalidate_icache(void)
}
/*
- * Flush all hypervisor mappings from the TLB and branch predictor of
- * the local processor.
- *
- * This is needed after changing Xen code mappings.
- *
- * The caller needs to issue the necessary DSB and D-cache flushes
- * before calling flush_xen_text_tlb.
+ * Invalidate all instruction caches on the local processor to PoU.
+ * We also need to flush the branch predictor for ARMv7 as it may be
+ * architecturally visible to the software (see B2.2.4 in ARM DDI 0406C.b).
*/
-static inline void flush_xen_text_tlb_local(void)
+static inline void invalidate_icache_local(void)
{
asm volatile (
- "isb;" /* Ensure synchronization with previous
changes to text */
- CMD_CP32(TLBIALLH) /* Flush hypervisor TLB */
- CMD_CP32(ICIALLU) /* Flush I-cache */
- CMD_CP32(BPIALL) /* Flush branch predictor */
- "dsb;" /* Ensure completion of TLB+BP flush */
- "isb;"
+ CMD_CP32(ICIALLU) /* Flush I-cache. */
+ CMD_CP32(BPIALL) /* Flush branch predictor. */
: : : "memory");
+
+ dsb(nsh); /* Ensure completion of the flush I-cache */
+ isb(); /* Synchronize fetched instruction stream. */
}
/*
diff --git a/xen/include/asm-arm/arm64/page.h b/xen/include/asm-arm/arm64/page.h
index 23d778154d..6c36d0210f 100644
--- a/xen/include/asm-arm/arm64/page.h
+++ b/xen/include/asm-arm/arm64/page.h
@@ -37,23 +37,12 @@ static inline void invalidate_icache(void)
isb();
}
-/*
- * Flush all hypervisor mappings from the TLB of the local processor.
- *
- * This is needed after changing Xen code mappings.
- *
- * The caller needs to issue the necessary DSB and D-cache flushes
- * before calling flush_xen_text_tlb.
- */
-static inline void flush_xen_text_tlb_local(void)
+/* Invalidate all instruction caches on the local processor to PoU */
+static inline void invalidate_icache_local(void)
{
- asm volatile (
- "isb;" /* Ensure synchronization with previous changes to text */
- "tlbi alle2;" /* Flush hypervisor TLB */
- "ic iallu;" /* Flush I-cache */
- "dsb sy;" /* Ensure completion of TLB flush */
- "isb;"
- : : : "memory");
+ asm volatile ("ic iallu");
+ dsb(nsh); /* Ensure completion of the I-cache flush */
+ isb();
}
/*
With minor notes,
Reviewed-by: Andrii Anisov <andrii_ani...@epam.com>
--
Sincerely,
Andrii Anisov.
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