From: Paolo Bonzini <pbonzini@redhat.com>
To: Bandan Das <bsd@redhat.com>, kvm@vger.kernel.org
Cc: guangrong.xiao@linux.intel.com, kernellwp@gmail.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/5] mmu: don't set the present bit unconditionally
Date: Wed, 13 Jul 2016 10:10:14 +0200 [thread overview]
Message-ID: <942237ee-a673-5cbf-0e7e-8e9075c904ec@redhat.com> (raw)
In-Reply-To: <1468361932-16580-3-git-send-email-bsd@redhat.com>
On 13/07/2016 00:18, Bandan Das wrote:
> + /*
> + * In the non-EPT case, execonly is not valid and so
> + * the following line is equivalent to spte |= PT_PRESENT_MASK.
I think the comment need not mention non-EPT.
> + * For the EPT case, shadow_present_mask is 0 if hardware
> + * supports it and we honor whatever way the guest set it.
if hardware supports exec-only page table entries.
> + * See: FNAME(gpte_access) in paging_tmpl.h
> + */
> + spte |= shadow_present_mask;
> if (!speculative)
> spte |= shadow_accessed_mask;
>
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index bc019f7..f2741db 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -181,13 +181,19 @@ no_present:
> return true;
> }
>
> +/*
> + * For PTTYPE_EPT, a page table can be executable but not readable
> + * on supported processors. Therefore, set_spte does not automatically
> + * set bit 0 if execute only is supported. Here, we repurpose ACC_USER_MASK
> + * to signify readability since it isn't used in the EPT case
> + */
> static inline unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, u64 gpte)
> {
> unsigned access;
> #if PTTYPE == PTTYPE_EPT
> access = ((gpte & VMX_EPT_WRITABLE_MASK) ? ACC_WRITE_MASK : 0) |
> ((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) |
> - ACC_USER_MASK;
> + ((gpte & VMX_EPT_READABLE_MASK) ? ACC_USER_MASK : 0);
> #else
> BUILD_BUG_ON(ACC_EXEC_MASK != PT_PRESENT_MASK);
> BUILD_BUG_ON(ACC_EXEC_MASK != 1);
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 64a79f2..f73b5dc 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6366,10 +6366,13 @@ static __init int hardware_setup(void)
> vmx_disable_intercept_msr_write_x2apic(0x83f);
>
> if (enable_ept) {
> - kvm_mmu_set_mask_ptes(0ull,
> + kvm_mmu_set_mask_ptes(VMX_EPT_READABLE_MASK,
> (enable_ept_ad_bits) ? VMX_EPT_ACCESS_BIT : 0ull,
> (enable_ept_ad_bits) ? VMX_EPT_DIRTY_BIT : 0ull,
> - 0ull, VMX_EPT_EXECUTABLE_MASK);
> + 0ull, VMX_EPT_EXECUTABLE_MASK,
> + cpu_has_vmx_ept_execute_only() ?
> + 0ull : PT_PRESENT_MASK);
Better to use VMX_EPT_READABLE_MASK here, which removes the need for the
BUILD_BUG_ON.
I can do these changes myself.
Paolo
> + BUILD_BUG_ON(PT_PRESENT_MASK != VMX_EPT_READABLE_MASK);
next prev parent reply other threads:[~2016-07-13 8:10 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-12 22:18 [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Bandan Das
2016-07-12 22:18 ` [PATCH v2 1/5] mmu: extend the is_present check to 32 bits Bandan Das
2016-09-01 14:20 ` Li, Liang Z
2016-09-01 15:16 ` Paolo Bonzini
2016-07-12 22:18 ` [PATCH v2 2/5] mmu: don't set the present bit unconditionally Bandan Das
2016-07-13 8:10 ` Paolo Bonzini [this message]
2016-07-12 22:18 ` [PATCH v2 3/5] mmu: remove is_present_gpte() Bandan Das
2016-07-12 22:18 ` [PATCH v2 4/5] mmu: change unconditional setting of the u bit in fault bitmap Bandan Das
2016-07-13 8:23 ` Paolo Bonzini
2016-07-13 9:06 ` Paolo Bonzini
2016-07-12 22:18 ` [PATCH v2 5/5] vmx: advertise support for ept execute only Bandan Das
2016-07-13 9:20 ` [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Paolo Bonzini
2016-07-13 9:49 ` Fam Zheng
2016-07-13 10:03 ` Paolo Bonzini
2016-07-13 15:06 ` Bandan Das
2016-07-13 15:27 ` Paolo Bonzini
2016-07-13 15:47 ` Bandan Das
2016-07-14 6:56 ` Paolo Bonzini
2016-07-14 17:38 ` Bandan Das
2016-07-14 18:29 ` Paolo Bonzini
2016-07-14 18:52 ` Bandan Das
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