diff mbox series

[v2,03/40] xen/arm: adjust Xen TLB helpers for Armv8-R64 PMSA

Message ID 20230113052914.3845596-4-Penny.Zheng@arm.com (mailing list archive)
State New, archived
Headers show
Series xen/arm: Add Armv8-R64 MPU support to Xen - Part#1 | expand

Commit Message

Penny Zheng Jan. 13, 2023, 5:28 a.m. UTC 
From: Wei Chen <wei.chen@arm.com>

From Arm ARM Supplement of Armv8-R AArch64 (DDI 0600A) [1],
section D1.6.2 TLB maintenance instructions, we know that
Armv8-R AArch64 permits an implementation to cache stage 1
VMSAv8-64 and stage 2 PMSAv8-64 attributes as a common entry
for the Secure EL1&0 translation regime. But for Xen itself,
it's running with stage 1 PMSAv8-64 on Armv8-R AArch64. The
EL2 MPU updates for stage 1 PMSAv8-64 will not be cached in
TLB entries. So we don't need any TLB invalidation for Xen
itself in EL2.

So in this patch, we use empty macros to stub Xen TLB helpers
for MPU system (PMSA), but still keep the Guest TLB helpers.
Because when a guest running in EL1 with VMSAv8-64 (MMU), guest
TLB invalidation is still needed. But we need some policy to
distinguish MPU and MMU guest, this will be done in guest
support of Armv8-R AArch64 later.

[1] https://developer.arm.com/documentation/ddi0600/ac

Signed-off-by: Wei Chen <wei.chen@arm.com>
---
v1 -> v2:
1. No change.
---
 xen/arch/arm/include/asm/arm64/flushtlb.h | 25 +++++++++++++++++++++++
 xen/arch/arm/include/asm/flushtlb.h       | 22 ++++++++++++++++++++
 2 files changed, 47 insertions(+)

Comments

Julien Grall Jan. 17, 2023, 11:16 p.m. UTC | #1 
Hi,

On 13/01/2023 05:28, Penny Zheng wrote:
> From: Wei Chen <wei.chen@arm.com>
> 
>  From Arm ARM Supplement of Armv8-R AArch64 (DDI 0600A) [1],
> section D1.6.2 TLB maintenance instructions, we know that
> Armv8-R AArch64 permits an implementation to cache stage 1
> VMSAv8-64 and stage 2 PMSAv8-64 attributes as a common entry
> for the Secure EL1&0 translation regime. But for Xen itself,
> it's running with stage 1 PMSAv8-64 on Armv8-R AArch64. The
> EL2 MPU updates for stage 1 PMSAv8-64 will not be cached in
> TLB entries. So we don't need any TLB invalidation for Xen
> itself in EL2.

So I understand the theory here. But I would expect that none of the 
common code will call any of those helpers. Therefore the #ifdef should 
be unnecessary.

Can you clarify if my understanding is correct?

Cheers,
Wei Chen Jan. 18, 2023, 2:32 a.m. UTC | #2 
Hi Julien,

> -----Original Message-----
> From: Julien Grall <julien@xen.org>
> Sent: 2023年1月18日 7:17
> To: Penny Zheng <Penny.Zheng@arm.com>; xen-devel@lists.xenproject.org
> Cc: Wei Chen <Wei.Chen@arm.com>; Stefano Stabellini
> <sstabellini@kernel.org>; Bertrand Marquis <Bertrand.Marquis@arm.com>;
> Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
> Subject: Re: [PATCH v2 03/40] xen/arm: adjust Xen TLB helpers for Armv8-
> R64 PMSA
> 
> Hi,
> 
> On 13/01/2023 05:28, Penny Zheng wrote:
> > From: Wei Chen <wei.chen@arm.com>
> >
> >  From Arm ARM Supplement of Armv8-R AArch64 (DDI 0600A) [1],
> > section D1.6.2 TLB maintenance instructions, we know that
> > Armv8-R AArch64 permits an implementation to cache stage 1
> > VMSAv8-64 and stage 2 PMSAv8-64 attributes as a common entry
> > for the Secure EL1&0 translation regime. But for Xen itself,
> > it's running with stage 1 PMSAv8-64 on Armv8-R AArch64. The
> > EL2 MPU updates for stage 1 PMSAv8-64 will not be cached in
> > TLB entries. So we don't need any TLB invalidation for Xen
> > itself in EL2.
> 
> So I understand the theory here. But I would expect that none of the
> common code will call any of those helpers. Therefore the #ifdef should
> be unnecessary.
> 
> Can you clarify if my understanding is correct?
> 

Yes, you're right, after we separate common code and MMU code, these
helpers will be called in MMU specific code only. We will drop this
patch in next version.

Cheers,
Wei Chen

> Cheers,
> 
> --
> Julien Grall
diff mbox series

Patch

diff --git a/xen/arch/arm/include/asm/arm64/flushtlb.h b/xen/arch/arm/include/asm/arm64/flushtlb.h
index 7c54315187..fe445f6831 100644
--- a/xen/arch/arm/include/asm/arm64/flushtlb.h
+++ b/xen/arch/arm/include/asm/arm64/flushtlb.h
@@ -51,6 +51,8 @@  TLB_HELPER(flush_all_guests_tlb_local, alle1);
 /* Flush innershareable TLBs, all VMIDs, non-hypervisor mode */
 TLB_HELPER(flush_all_guests_tlb, alle1is);
 
+#ifndef CONFIG_HAS_MPU
+
 /* Flush all hypervisor mappings from the TLB of the local processor. */
 TLB_HELPER(flush_xen_tlb_local, alle2);
 
@@ -66,6 +68,29 @@  static inline void __flush_xen_tlb_one(vaddr_t va)
     asm volatile("tlbi vae2is, %0;" : : "r" (va>>PAGE_SHIFT) : "memory");
 }
 
+#else
+
+/*
+ * When Xen is running with stage 1 PMSAv8-64 on MPU systems. The EL2 MPU
+ * updates for stage1 PMSAv8-64 will not be cached in TLB entries. So we
+ * don't need any TLB invalidation for Xen itself in EL2. See Arm ARM
+ * Supplement of Armv8-R AArch64 (DDI 0600A), section D1.6.2 TLB maintenance
+ * instructions for more details.
+ */
+static inline void flush_xen_tlb_local(void)
+{
+}
+
+static inline void  __flush_xen_tlb_one_local(vaddr_t va)
+{
+}
+
+static inline void __flush_xen_tlb_one(vaddr_t va)
+{
+}
+
+#endif /* CONFIG_HAS_MPU */
+
 #endif /* __ASM_ARM_ARM64_FLUSHTLB_H__ */
 /*
  * Local variables:
diff --git a/xen/arch/arm/include/asm/flushtlb.h b/xen/arch/arm/include/asm/flushtlb.h
index 125a141975..4b8bf65281 100644
--- a/xen/arch/arm/include/asm/flushtlb.h
+++ b/xen/arch/arm/include/asm/flushtlb.h
@@ -28,6 +28,7 @@  static inline void page_set_tlbflush_timestamp(struct page_info *page)
 /* Flush specified CPUs' TLBs */
 void arch_flush_tlb_mask(const cpumask_t *mask);
 
+#ifndef CONFIG_HAS_MPU
 /*
  * Flush a range of VA's hypervisor mappings from the TLB of the local
  * processor.
@@ -66,6 +67,27 @@  static inline void flush_xen_tlb_range_va(vaddr_t va,
     isb();
 }
 
+#else
+
+/*
+ * When Xen is running with stage 1 PMSAv8-64 on MPU systems. The EL2 MPU
+ * updates for stage1 PMSAv8-64 will not be cached in TLB entries. So we
+ * don't need any TLB invalidation for Xen itself in EL2. See Arm ARM
+ * Supplement of Armv8-R AArch64 (DDI 0600A), section D1.6.2 TLB maintenance
+ * instructions for more details.
+ */
+static inline void flush_xen_tlb_range_va_local(vaddr_t va,
+                                                unsigned long size)
+{
+}
+
+static inline void flush_xen_tlb_range_va(vaddr_t va,
+                                          unsigned long size)
+{
+}
+
+#endif /* CONFIG_HAS_MPU */
+
 #endif /* __ASM_ARM_FLUSHTLB_H__ */
 /*
  * Local variables: