From: Yu Zhang <yu.c.zhang@linux.intel.com>
To: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, linux-mm@kvack.org, luto@kernel.org,
peterz@infradead.org, dave.hansen@intel.com, pbonzini@redhat.com,
sean.j.christopherson@intel.com, keescook@chromium.org,
kristen@linux.intel.com, deneen.t.dock@intel.com
Subject: Re: [RFC PATCH 01/13] kvm: Enable MTRR to work with GFNs with perm bits
Date: Mon, 14 Oct 2019 14:47:53 +0800 [thread overview]
Message-ID: <20191014064753.xv365y6oowmh6ho7@linux.intel.com> (raw)
In-Reply-To: <20191003212400.31130-2-rick.p.edgecombe@intel.com>
On Thu, Oct 03, 2019 at 02:23:48PM -0700, Rick Edgecombe wrote:
> Mask gfn by maxphyaddr in kvm_mtrr_get_guest_memory_type so that the
> guests view of gfn is used when high bits of the physical memory are
> used as extra permissions bits. This supports the KVM XO feature.
>
> TODO: Since MTRR is emulated using EPT permissions, the XO version of
> the gpa range will not inherrit the MTRR type with this implementation.
> There shouldn't be any legacy use of KVM XO, but hypothetically it could
> interfere with the uncacheable MTRR type.
>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> ---
> arch/x86/kvm/mtrr.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
> index 25ce3edd1872..da38f3b83e51 100644
> --- a/arch/x86/kvm/mtrr.c
> +++ b/arch/x86/kvm/mtrr.c
> @@ -621,6 +621,14 @@ u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
> const int wt_wb_mask = (1 << MTRR_TYPE_WRBACK)
> | (1 << MTRR_TYPE_WRTHROUGH);
>
> + /*
> + * Handle situations where gfn bits are used as permissions bits by
> + * masking KVMs view of the gfn with the guests physical address bits
> + * in order to match the guests view of physical address. For normal
> + * situations this will have no effect.
> + */
> + gfn &= (1ULL << (cpuid_maxphyaddr(vcpu) - PAGE_SHIFT));
> +
Won't this break the MTRR calculation for normal gfns?
Are you suggesting use the same MTRR value for the XO range as the normal one's?
If so, may be we should use:
if (guest_cpuid_has(vcpu, X86_FEATURE_KVM_XO))
gfn &= ~(1ULL << (cpuid_maxphyaddr(vcpu) - PAGE_SHIFT));
> start = gfn_to_gpa(gfn);
> end = start + PAGE_SIZE;
>
> --
> 2.17.1
>
B.R.
Yu
next prev parent reply other threads:[~2019-10-14 6:56 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 21:23 [RFC PATCH 00/13] XOM for KVM guest userspace Rick Edgecombe
2019-10-03 21:23 ` [RFC PATCH 01/13] kvm: Enable MTRR to work with GFNs with perm bits Rick Edgecombe
2019-10-14 6:47 ` Yu Zhang [this message]
2019-10-14 18:44 ` Edgecombe, Rick P
2019-10-03 21:23 ` [RFC PATCH 02/13] kvm: Add support for X86_FEATURE_KVM_XO Rick Edgecombe
2019-10-03 21:23 ` [RFC PATCH 03/13] kvm: Add XO memslot type Rick Edgecombe
2019-10-04 7:27 ` Paolo Bonzini
2019-10-04 19:06 ` Edgecombe, Rick P
2019-10-06 16:15 ` Paolo Bonzini
2019-10-03 21:23 ` [RFC PATCH 04/13] kvm, vmx: Add support for gva exit qualification Rick Edgecombe
2019-10-03 21:23 ` [RFC PATCH 05/13] kvm: Add #PF injection for KVM XO Rick Edgecombe
2019-10-04 7:42 ` Paolo Bonzini
2019-10-04 19:11 ` Edgecombe, Rick P
2019-10-03 21:23 ` [RFC PATCH 06/13] kvm: Add KVM_CAP_EXECONLY_MEM Rick Edgecombe
2019-10-04 7:24 ` Paolo Bonzini
2019-10-04 19:11 ` Edgecombe, Rick P
2019-10-03 21:23 ` [RFC PATCH 07/13] kvm: Add docs for KVM_CAP_EXECONLY_MEM Rick Edgecombe
2019-10-03 21:23 ` [RFC PATCH 08/13] x86/boot: Rename USE_EARLY_PGTABLE_L5 Rick Edgecombe
2019-10-03 21:23 ` [RFC PATCH 09/13] x86/cpufeature: Add detection of KVM XO Rick Edgecombe
2019-10-29 23:33 ` Kees Cook
2019-10-29 23:52 ` Edgecombe, Rick P
2019-10-30 14:55 ` Sean Christopherson
2019-10-30 21:02 ` Edgecombe, Rick P
2019-10-03 21:23 ` [RFC PATCH 10/13] x86/mm: Add NR page bit for " Rick Edgecombe
2019-10-04 7:33 ` Paolo Bonzini
2019-10-03 21:23 ` [RFC PATCH 11/13] x86, ptdump: Add NR bit to page table dump Rick Edgecombe
2019-10-03 21:23 ` [RFC PATCH 12/13] mmap: Add XO support for KVM XO Rick Edgecombe
2019-10-04 7:34 ` Paolo Bonzini
2019-10-04 19:12 ` Edgecombe, Rick P
2019-10-03 21:24 ` [RFC PATCH 13/13] x86/Kconfig: Add Kconfig for KVM based XO Rick Edgecombe
2019-10-29 23:36 ` Kees Cook
2019-10-30 0:01 ` Edgecombe, Rick P
2019-10-30 18:36 ` Kees Cook
2019-10-04 7:22 ` [RFC PATCH 00/13] XOM for KVM guest userspace Paolo Bonzini
2019-10-04 19:03 ` Edgecombe, Rick P
2019-10-04 14:56 ` Andy Lutomirski
2019-10-04 20:09 ` Edgecombe, Rick P
2019-10-05 1:33 ` Andy Lutomirski
2019-10-07 18:14 ` Edgecombe, Rick P
2019-10-29 23:40 ` Kees Cook
2019-10-30 0:27 ` Edgecombe, Rick P
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