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Re: [Xen-devel] [PATCH 01/10] VMX: Enable EPT A/D bit support
On 03/28/2015 04:38 AM, Andrew Cooper wrote:
On 27/03/15 02:35, Kai Huang wrote:
PML requires A/D bit support so enable it for further use.
Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
---
xen/arch/x86/hvm/vmx/vmcs.c | 1 +
xen/arch/x86/mm/p2m-ept.c | 8 +++++++-
xen/include/asm-x86/hvm/vmx/vmcs.h | 4 +++-
xen/include/asm-x86/hvm/vmx/vmx.h | 5 ++++-
4 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index d614638..2f645fe 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -103,6 +103,7 @@ static void __init vmx_display_features(void)
P(cpu_has_vmx_tpr_shadow, "APIC TPR shadow");
P(cpu_has_vmx_ept, "Extended Page Tables (EPT)");
P(cpu_has_vmx_vpid, "Virtual-Processor Identifiers (VPID)");
+ P(cpu_has_vmx_ept_ad_bit, "EPT A/D bit");
P(cpu_has_vmx_vnmi, "Virtual NMI");
P(cpu_has_vmx_msr_bitmap, "MSR direct-access bitmap");
P(cpu_has_vmx_unrestricted_guest, "Unrestricted Guest");
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index c2d7720..8650092 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -233,6 +233,9 @@ static int ept_split_super_page(struct p2m_domain *p2m,
ept_entry_t *ept_entry,
if ( !ept_set_middle_entry(p2m, &new_ept) )
return 0;
+ /* It's better to copy A bit of Middle entry from original entry */
+ new_ept.a = ept_entry->a;
Surely d needs to be propagated as well? Would it make sense to extend
ept_set_middle_entry() to do all of new_ept setup in one location?
+
table = map_domain_page(new_ept.mfn);
trunk = 1UL << ((level - 1) * EPT_TABLE_ORDER);
@@ -244,7 +247,7 @@ static int ept_split_super_page(struct p2m_domain *p2m, ept_entry_t *ept_entry,
epte->sp = (level > 1);
epte->mfn += i * trunk;
epte->snp = (iommu_enabled && iommu_snoop);
- ASSERT(!epte->rsvd1);
+ /* A/D bits are inherited from superpage */
ASSERT(!epte->avail3);
ept_p2m_type_to_flags(epte, epte->sa_p2mt, epte->access);
@@ -1071,6 +1074,9 @@ int ept_p2m_init(struct p2m_domain *p2m)
/* set EPT page-walk length, now it's actual walk length - 1, i.e. 3 */
ept->ept_wl = 3;
+ /* Enable EPT A/D bit if it's supported by hardware */
+ ept->ept_ad = cpu_has_vmx_ept_ad_bit ? 1 : 0;
This will incur overhead on all EPT operations. It should only be
enabled if pml is going to be in use. (I think you need reverse patches
1 and 2 in the series, and gate on pml_enable here)
Hi Andrew,
I'd like to also put patch 3 (PML feature detection) before this patch,
as it's better to use cpu_has_vmx_pml to gate A/D bit enabling here.
Theoretically simple "pml_enable = 1" here doesn't guarantee
cpu_has_vmx_pml to be true, as PML may be turned off during
vmx_init_vmcs_config.
And in this case I also want to delete below code, as if PML is not
enabled, below code will print but actually EPT A/D bits is not enabled
in hardware.
P(cpu_has_vmx_ept_ad, "EPT A/D bit");
Thanks,
-Kai
+
if ( !zalloc_cpumask_var(&ept->synced_mask) )
return -ENOMEM;
diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h b/xen/include/asm-x86/hvm/vmx/vmcs.h
index 6fce6aa..4528346 100644
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
@@ -62,7 +62,8 @@ struct ept_data {
struct {
u64 ept_mt :3,
ept_wl :3,
- rsvd :6,
+ ept_ad :1,
+ rsvd :5,
asr :52;
While you are making this change, can you add comments similar to
ept_entry_t describing the bits?
};
u64 eptp;
@@ -226,6 +227,7 @@ extern u32 vmx_secondary_exec_control;
#define VMX_EPT_INVEPT_INSTRUCTION 0x00100000
#define VMX_EPT_INVEPT_SINGLE_CONTEXT 0x02000000
#define VMX_EPT_INVEPT_ALL_CONTEXT 0x04000000
+#define VMX_EPT_AD_BIT_SUPPORT 0x00200000
#define VMX_MISC_VMWRITE_ALL 0x20000000
diff --git a/xen/include/asm-x86/hvm/vmx/vmx.h b/xen/include/asm-x86/hvm/vmx/vmx.h
index 91c5e18..9afd351 100644
--- a/xen/include/asm-x86/hvm/vmx/vmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vmx.h
@@ -37,7 +37,8 @@ typedef union {
emt : 3, /* bits 5:3 - EPT Memory type */
ipat : 1, /* bit 6 - Ignore PAT memory type */
sp : 1, /* bit 7 - Is this a superpage? */
- rsvd1 : 2, /* bits 9:8 - Reserved for future use */
+ a : 1, /* bit 8 - Access bit */
+ d : 1, /* bit 9 - Dirty bit */
recalc : 1, /* bit 10 - Software available 1 */
snp : 1, /* bit 11 - VT-d snoop control in shared
EPT/VT-d usage */
@@ -261,6 +262,8 @@ extern uint8_t posted_intr_vector;
(vmx_ept_vpid_cap & VMX_EPT_SUPERPAGE_2MB)
#define cpu_has_vmx_ept_invept_single_context \
(vmx_ept_vpid_cap & VMX_EPT_INVEPT_SINGLE_CONTEXT)
+#define cpu_has_vmx_ept_ad_bit \
+ (vmx_ept_vpid_cap & VMX_EPT_AD_BIT_SUPPORT)
I think cpu_has_vmx_ept_ad is sufficient, without the _bit suffix making
it longer.
~Andrew
#define EPT_2MB_SHIFT 16
#define EPT_1GB_SHIFT 17
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