[PATCH 1/5] KVM: vmx: fix ept reserved bits for 1-GByte page
EPT misconfig handler in kvm will check which reason lead to EPT
misconfiguration after vmexit. One of the reasons is that an EPT
paging-structure entry is configured with settings reserved for
future functionality. However, the handler can't identify if
paging-structure entry of reserved bits for 1-GByte page are
configured, since PDPTE which point to 1-GByte page will reserve
bits 29:12 instead of bits 7:3 which are reserved for PDPTE that
references an EPT Page Directory. This patch fix it by reserve
bits 29:12 for 1-GByte page.
Signed-off-by: Wanpeng Li
---
arch/x86/kvm/vmx.c | 14 ++
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index bfe11cf..71cbee5 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5521,9 +5521,14 @@ static u64 ept_rsvd_mask(u64 spte, int level)
for (i = 51; i > boot_cpu_data.x86_phys_bits; i--)
mask |= (1ULL << i);
- if (level > 2)
- /* bits 7:3 reserved */
- mask |= 0xf8;
+ if (level > 2) {
+ if (spte & (1 << 7))
+ /* 1GB ref, bits 29:12 */
+ mask |= 0x3000;
+ else
+ /* bits 7:3 reserved */
+ mask |= 0xf8;
+ }
else if (level == 2) {
if (spte & (1ULL << 7))
/* 2MB ref, bits 20:12 reserved */
@@ -5561,7 +5566,8 @@ static void ept_misconfig_inspect_spte(struct kvm_vcpu
*vcpu, u64 spte,
WARN_ON(1);
}
- if (level == 1 || (level == 2 && (spte & (1ULL << 7 {
+ if (level == 1 || ((level == 3 || level == 2)
+ && (spte & (1ULL << 7 {
u64 ept_mem_type = (spte & 0x38) >> 3;
if (ept_mem_type == 2 || ept_mem_type == 3 ||
--
1.9.1
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Re: [PATCH 1/5] KVM: vmx: fix ept reserved bits for 1-GByte page
Il 18/08/2014 11:50, Wanpeng Li ha scritto:
> EPT misconfig handler in kvm will check which reason lead to EPT
> misconfiguration after vmexit. One of the reasons is that an EPT
> paging-structure entry is configured with settings reserved for
> future functionality. However, the handler can't identify if
> paging-structure entry of reserved bits for 1-GByte page are
> configured, since PDPTE which point to 1-GByte page will reserve
> bits 29:12 instead of bits 7:3 which are reserved for PDPTE that
> references an EPT Page Directory. This patch fix it by reserve
> bits 29:12 for 1-GByte page.
>
> Signed-off-by: Wanpeng Li
> ---
> arch/x86/kvm/vmx.c | 14 ++
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index bfe11cf..71cbee5 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5521,9 +5521,14 @@ static u64 ept_rsvd_mask(u64 spte, int level)
> for (i = 51; i > boot_cpu_data.x86_phys_bits; i--)
> mask |= (1ULL << i);
>
> - if (level > 2)
> - /* bits 7:3 reserved */
> - mask |= 0xf8;
> + if (level > 2) {
level can be 4 here. You have to return 0xf8 for level == 4.
The same "if" statement then can cover both 2MB and 1GB pages, like
if (spte & (1ULL << 7))
/* 1GB/2MB page, bits 29:12 or 20:12 reserved
respectively */
mask |= (PAGE_SIZE << ((level - 1) * 9)) - PAGE_SIZE;
else
/* bits 6:3 reserved */
mask |= 0x78;
> - if (level == 1 || (level == 2 && (spte & (1ULL << 7 {
> + if (level == 1 || ((level == 3 || level == 2)
> + && (spte & (1ULL << 7 {
This condition can be simplified by checking the return value of ept_rsvd_mask.
If it includes 0x38, this is a large page. Otherwise it is a leaf page and
you can go down the "if".
Paolo
> u64 ept_mem_type = (spte & 0x38) >> 3;
>
> if (ept_mem_type == 2 || ept_mem_type == 3 ||
>
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Re: [PATCH 1/5] KVM: vmx: fix ept reserved bits for 1-GByte page
On 08/18/2014 05:50 PM, Wanpeng Li wrote: > EPT misconfig handler in kvm will check which reason lead to EPT > misconfiguration after vmexit. One of the reasons is that an EPT > paging-structure entry is configured with settings reserved for > future functionality. However, the handler can't identify if > paging-structure entry of reserved bits for 1-GByte page are > configured, since PDPTE which point to 1-GByte page will reserve > bits 29:12 instead of bits 7:3 which are reserved for PDPTE that > references an EPT Page Directory. This patch fix it by reserve > bits 29:12 for 1-GByte page. That mask is only set in the lowest pte for 4K page, i think it is not a problem, no? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 1/5] KVM: vmx: fix ept reserved bits for 1-GByte page
Il 18/08/2014 12:52, Xiao Guangrong ha scritto: >> > EPT misconfig handler in kvm will check which reason lead to EPT >> > misconfiguration after vmexit. One of the reasons is that an EPT >> > paging-structure entry is configured with settings reserved for >> > future functionality. However, the handler can't identify if >> > paging-structure entry of reserved bits for 1-GByte page are >> > configured, since PDPTE which point to 1-GByte page will reserve >> > bits 29:12 instead of bits 7:3 which are reserved for PDPTE that >> > references an EPT Page Directory. This patch fix it by reserve >> > bits 29:12 for 1-GByte page. > That mask is only set in the lowest pte for 4K page, i think it > is not a problem, no? It will cause KVM to WARN. The EPT memory type will also be ignored for gigabyte pages. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 1/5] KVM: vmx: fix ept reserved bits for 1-GByte page
Hi Paolo,
On Mon, Aug 18, 2014 at 12:18:59PM +0200, Paolo Bonzini wrote:
>Il 18/08/2014 11:50, Wanpeng Li ha scritto:
>> EPT misconfig handler in kvm will check which reason lead to EPT
>> misconfiguration after vmexit. One of the reasons is that an EPT
>> paging-structure entry is configured with settings reserved for
>> future functionality. However, the handler can't identify if
>> paging-structure entry of reserved bits for 1-GByte page are
>> configured, since PDPTE which point to 1-GByte page will reserve
>> bits 29:12 instead of bits 7:3 which are reserved for PDPTE that
>> references an EPT Page Directory. This patch fix it by reserve
>> bits 29:12 for 1-GByte page.
>>
>> Signed-off-by: Wanpeng Li
>> ---
>> arch/x86/kvm/vmx.c | 14 ++
>> 1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index bfe11cf..71cbee5 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -5521,9 +5521,14 @@ static u64 ept_rsvd_mask(u64 spte, int level)
>> for (i = 51; i > boot_cpu_data.x86_phys_bits; i--)
>> mask |= (1ULL << i);
>>
>> -if (level > 2)
>> -/* bits 7:3 reserved */
>> -mask |= 0xf8;
>> +if (level > 2) {
>
>level can be 4 here. You have to return 0xf8 for level == 4.
>
>The same "if" statement then can cover both 2MB and 1GB pages, like
>
>if (spte & (1ULL << 7))
>/* 1GB/2MB page, bits 29:12 or 20:12 reserved
> respectively */
>mask |= (PAGE_SIZE << ((level - 1) * 9)) - PAGE_SIZE;
>else
>/* bits 6:3 reserved */
>mask |= 0x78;
>
>> -if (level == 1 || (level == 2 && (spte & (1ULL << 7 {
>> +if (level == 1 || ((level == 3 || level == 2)
>> +&& (spte & (1ULL << 7 {
>
>This condition can be simplified by checking the return value of ept_rsvd_mask.
>If it includes 0x38, this is a large page. Otherwise it is a leaf page and
>you can go down the "if".
As you know, 5:3 bits which used for EPT MT are not reserved bits, so
I fail to understand why check the return value of ept_rsvd_mask and
it's a large page if includes 0x38. Could you eplain in more details? ;-)
Regards,
Wanpeng Li
>
>Paolo
>
>> u64 ept_mem_type = (spte & 0x38) >> 3;
>>
>> if (ept_mem_type == 2 || ept_mem_type == 3 ||
>>
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Re: [PATCH 1/5] KVM: vmx: fix ept reserved bits for 1-GByte page
Il 19/08/2014 04:17, Wanpeng Li ha scritto:
>>> >> -if (level == 1 || (level == 2 && (spte & (1ULL << 7
>>> >> {
>>> >> +if (level == 1 || ((level == 3 || level == 2)
>>> >> +&& (spte & (1ULL << 7 {
>> >
>> >This condition can be simplified by checking the return value of
>> >ept_rsvd_mask.
>> >If it includes 0x38, this is a large page.
Oops, a "not" was missing. If it includes 0x38, this is _not_ a large
page (it is a page directory / page directory pointer / PML4).
>> Otherwise it is a leaf page and
>> you can go down the "if".
> As you know, 5:3 bits which used for EPT MT are not reserved bits, so
> I fail to understand why check the return value of ept_rsvd_mask and
> it's a large page if includes 0x38. Could you eplain in more details? ;-)
A non-leaf page will always have 0x38 in the ept_rsvd_mask. A leaf page
will never have 0x38 in the ept_rsvd_mask.
Paolo
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