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Re: [Xen-devel] [PATCH v2] xen/arm: Add support for 16 bit VMIDs
Hi Bhupinder,
On 25/11/16 10:33, Bhupinder Thakur wrote:
VMID space is increased to 16-bits from 8-bits in ARMv8 8.1 revision.
This allows more than 256 VMs to be supported by Xen.
This change adds support for 16-bit VMIDs in Xen based on whether the
architecture supports it.
Signed-off-by: Bhupinder Thakur <bhupinder.thakur@xxxxxxxxxx>
Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
The tag reviewed-by has a strong meaning, it means that the person has
fully reviewed the code and he agrees with the modifications (i.e the
code is good to be pushed). For more details see a good description in
in Linux doc (see [1]).
In this case, neither Stefano nor I gave it. So please drop them until
one of us formally gave him. (e.g Reviewed-by: Name <email>).
---
xen/arch/arm/p2m.c | 68 ++++++++++++++++++++++++++++++++++++-----
xen/arch/arm/setup.c | 3 +-
xen/include/asm-arm/p2m.h | 4 +--
xen/include/asm-arm/processor.h | 18 ++++++++++-
4 files changed, 82 insertions(+), 11 deletions(-)
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index cc5634b..f036cfb 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -7,6 +7,7 @@
#include <xen/vm_event.h>
#include <xen/monitor.h>
#include <xen/iocap.h>
+#include <xen/xmalloc.h>
#include <public/vm_event.h>
#include <asm/flushtlb.h>
#include <asm/gic.h>
@@ -19,6 +20,7 @@ static unsigned int __read_mostly p2m_root_order;
static unsigned int __read_mostly p2m_root_level;
#define P2M_ROOT_ORDER p2m_root_order
#define P2M_ROOT_LEVEL p2m_root_level
+static unsigned int __read_mostly max_vmid;
I would much prefer if max_vmid and MAX_VMID are defined together.
#else
/* First level P2M is alway 2 consecutive pages */
#define P2M_ROOT_LEVEL 1
@@ -1219,7 +1221,7 @@ static int p2m_alloc_table(struct domain *d)
p2m->root = page;
- p2m->vttbr = page_to_maddr(p2m->root) | ((uint64_t)p2m->vmid & 0xff) << 48;
+ p2m->vttbr = page_to_maddr(p2m->root) | ((uint64_t)p2m->vmid << 48);
/*
* Make sure that all TLBs corresponding to the new VMID are flushed
@@ -1230,20 +1232,68 @@ static int p2m_alloc_table(struct domain *d)
return 0;
}
-#define MAX_VMID 256
+#define MAX_VMID_8_BIT (1UL << 8)
+#define MAX_VMID_16_BIT (1UL << 16)
+
+#ifdef CONFIG_ARM_64
+#define MAX_VMID max_vmid
+#else
+#define MAX_VMID MAX_VMID_8_BIT
+#endif
+
#define INVALID_VMID 0 /* VMID 0 is reserved */
static spinlock_t vmid_alloc_lock = SPIN_LOCK_UNLOCKED;
/*
- * VTTBR_EL2 VMID field is 8 bits. Using a bitmap here limits us to
- * 256 concurrent domains.
+ * VTTBR_EL2 VMID field is 8 or 16 bits. Aarch64 supports 16-bit VMID.
+ * Using a bitmap here limits us to 256 or 65536 (for Aarch64) concurrent
+ * domains. The bitmap space will be allocated dynamically based on
+ * whether 8 or 16 bit VMIDs are supported.
*/
-static DECLARE_BITMAP(vmid_mask, MAX_VMID);
+static unsigned long *vmid_mask=NULL;
Coding style here.
vmid_mask = NULL;
However, the NULL is not necessary here as global variable are
initialized to 0 by default.
-void p2m_vmid_allocator_init(void)
+int p2m_vmid_allocator_init(void)
{
- set_bit(INVALID_VMID, vmid_mask);
+ int ret=0;
Coding style;
int ret = 0;
+
+#ifdef CONFIG_ARM_64
+
+ unsigned int cpu;
+
+ /*
+ * initialize max_vmid to 16 bits by default
+ */
+ max_vmid = MAX_VMID_16_BIT;
This could be done at the declaration of max_vmid.
+
+ /*
+ * if any cpu does not support 16-bit VMID then restrict the
+ * max VMIDs which can be allocated to 256
+ */
+ for_each_online_cpu ( cpu )
+ {
+ const struct cpuinfo_arm *info = &cpu_data[cpu];
+
+ if ( info->mm64.vmid_bits != MM64_VMID_16_BITS_SUPPORT )
+ {
+ max_vmid = MAX_VMID_8_BIT;
+ break;
+ }
+ }
I still think this is very confusing to consider 16-bit VMID by default
as this is an enhancement in a newer architecture.
I would prefer to see the loop inverted, i.e checking whether all the
CPUs support 16-bit and set max_vmid to 16 bit if supported.
If you disagree please explain why.
+
+#endif
+
+ /*
+ * allocate space for vmid_mask based on max_vmid
+ */
+ vmid_mask = xzalloc_array(unsigned long, BITS_TO_LONGS(MAX_VMID));
+
+ if ( vmid_mask )
+ set_bit(INVALID_VMID, vmid_mask);
+ else
+ ret = -1;
+
+ return ret;
}
static int p2m_alloc_vmid(struct domain *d)
@@ -1646,6 +1696,10 @@ void __init setup_virt_paging(void)
val |= VTCR_PS(pa_range);
val |= VTCR_TG0_4K;
+
+ /* set the VS bit only if 16 bit VMID is supported */
+ if ( MAX_VMID == MAX_VMID_16_BIT )
+ val |= VTCR_VS;
val |= VTCR_SL0(pa_range_info[pa_range].sl0);
val |= VTCR_T0SZ(pa_range_info[pa_range].t0sz);
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 38eb888..e240b12 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -789,7 +789,8 @@ void __init start_xen(unsigned long boot_phys_offset,
gic_init();
- p2m_vmid_allocator_init();
+ if ( p2m_vmid_allocator_init() != 0 )
+ panic("Could not allocate VMID bitmap space");
I am not sure why we have to initialize the VMID allocator far before
setting up the stage-2 translation (see call setup_virt_paging).
Overall, VMID are part of stage-2 subsystem. So I think it would be
better to move this call in setup_virt_paging.
With that you could take advantage of the for_each_online loop in
setup_virt_paging and avoid to have go through again all CPUs.
So what I would like to see is:
- Patch #1: move p2m_vmid_allocator_init in setup_virt_paging
- Patch #2: Add support for 16 bit VMIDs
softirq_init();
diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index fdb6b47..b998e69 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -30,7 +30,7 @@ struct p2m_domain {
struct page_info *root;
/* Current VMID in use */
- uint8_t vmid;
+ uint16_t vmid;
/* Current Translation Table Base Register for the p2m */
uint64_t vttbr;
@@ -153,7 +153,7 @@ void p2m_altp2m_check(struct vcpu *v, uint16_t idx)
}
/* Initialise vmid allocator */
-void p2m_vmid_allocator_init(void);
+int p2m_vmid_allocator_init(void);
/* Second stage paging setup, to be called on all CPUs */
void setup_virt_paging(void);
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index 15bf890..48ce59b 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -215,6 +215,8 @@
#define VTCR_PS(x) ((x)<<16)
+#define VTCR_VS (_AC(0x1,UL)<<19)
+
#endif
#define VTCR_RES1 (_AC(1,UL)<<31)
@@ -269,6 +271,11 @@
/* FSR long format */
#define FSRL_STATUS_DEBUG (_AC(0x22,UL)<<0)
+#ifdef CONFIG_ARM_64
+#define MM64_VMID_8_BITS_SUPPORT 0x0
+#define MM64_VMID_16_BITS_SUPPORT 0x2
+#endif
+
#ifndef __ASSEMBLY__
struct cpuinfo_arm {
@@ -337,7 +344,16 @@ struct cpuinfo_arm {
unsigned long tgranule_64K:4;
unsigned long tgranule_4K:4;
unsigned long __res0:32;
- };
+
+ unsigned long hafdbs:4;
+ unsigned long vmid_bits:4;
+ unsigned long vh:4;
+ unsigned long hpds:4;
+ unsigned long lo:4;
+ unsigned long pan:4;
+ unsigned long __res1:8;
+ unsigned long __res2:32;
+ };
} mm64;
struct {
[1] https://www.kernel.org/doc/Documentation/SubmittingPatches
--
Julien Grall
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