From: Paolo Bonzini <pbonzini@redhat.com>
To: Yang Weijiang <weijiang.yang@intel.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
sean.j.christopherson@intel.com
Cc: mst@redhat.com, rkrcmar@redhat.com, jmattson@google.com,
yu.c.zhang@intel.com, alazar@bitdefender.com
Subject: Re: [PATCH RESEND v4 7/9] KVM: VMX: Handle SPP induced vmexit and page fault
Date: Mon, 19 Aug 2019 17:04:23 +0200 [thread overview]
Message-ID: <fb6cd8b4-eee9-6e58-4047-550811bffd58@redhat.com> (raw)
In-Reply-To: <5f6ba406-17c4-a552-2352-2ff50569aac0@redhat.com>
On 19/08/19 16:43, Paolo Bonzini wrote:
>> + /*
>> + * Record write protect fault caused by
>> + * Sub-page Protection, let VMI decide
>> + * the next step.
>> + */
>> + if (spte & PT_SPP_MASK) {
> Should this be "if (spte & PT_WRITABLE_MASK)" instead? That is, if the
> page is already writable, the fault must be an SPP fault.
Hmm, no I forgot how SPP works; still, this is *not* correct. For
example, if SPP marks part of a page as read-write, but KVM wants to
write-protect the whole page for access or dirty tracking, that should
not cause an SPP exit.
So I think that when KVM wants to write-protect the whole page
(wrprot_ad_disabled_spte) it must also clear PT_SPP_MASK; for example it
could save it in bit 53 (PT64_SECOND_AVAIL_BITS_SHIFT + 1). If the
saved bit is set, fast_page_fault must then set PT_SPP_MASK instead of
PT_WRITABLE_MASK. On re-entry this will cause an SPP vmexit;
fast_page_fault should never trigger an SPP userspace exit on its own,
all the SPP handling should go through handle_spp.
Paolo
next prev parent reply other threads:[~2019-08-19 15:04 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 7:03 [PATCH RESEND v4 0/9] Enable Sub-page Write Protection Support Yang Weijiang
2019-08-14 7:03 ` [PATCH RESEND v4 1/9] Documentation: Introduce EPT based Subpage Protection Yang Weijiang
2019-08-14 7:03 ` [PATCH RESEND v4 2/9] KVM: VMX: Add control flags for SPP enabling Yang Weijiang
2019-08-14 7:03 ` [PATCH RESEND v4 3/9] KVM: VMX: Implement functions for SPPT paging setup Yang Weijiang
2019-08-14 7:03 ` [PATCH RESEND v4 4/9] KVM: VMX: Introduce SPP access bitmap and operation functions Yang Weijiang
2019-08-14 7:03 ` [PATCH RESEND v4 5/9] KVM: VMX: Add init/set/get functions for SPP Yang Weijiang
2019-08-14 12:43 ` Vitaly Kuznetsov
2019-08-14 14:34 ` Yang Weijiang
2019-08-15 13:43 ` Yang Weijiang
2019-08-15 14:03 ` Vitaly Kuznetsov
2019-08-19 14:06 ` Yang Weijiang
2019-08-15 16:25 ` Jim Mattson
2019-08-15 16:38 ` Sean Christopherson
2019-08-16 13:31 ` Yang Weijiang
2019-08-16 18:19 ` Jim Mattson
2019-08-19 2:08 ` Yang Weijiang
2019-08-19 15:15 ` Paolo Bonzini
2019-08-20 12:33 ` Yang Weijiang
2019-08-19 15:05 ` Paolo Bonzini
2019-08-20 12:36 ` Yang Weijiang
2019-08-19 15:13 ` Paolo Bonzini
2019-08-20 13:09 ` Yang Weijiang
2019-08-14 7:04 ` [PATCH RESEND v4 6/9] KVM: VMX: Introduce SPP user-space IOCTLs Yang Weijiang
2019-08-14 7:04 ` [PATCH RESEND v4 7/9] KVM: VMX: Handle SPP induced vmexit and page fault Yang Weijiang
2019-08-19 14:43 ` Paolo Bonzini
2019-08-19 15:04 ` Paolo Bonzini [this message]
2019-08-20 13:44 ` Yang Weijiang
2019-08-22 13:17 ` Yang Weijiang
2019-08-22 16:38 ` Paolo Bonzini
2019-08-23 0:26 ` Yang Weijiang
2019-08-14 7:04 ` [PATCH RESEND v4 8/9] KVM: MMU: Enable Lazy mode SPPT setup Yang Weijiang
2019-08-19 14:46 ` Paolo Bonzini
2019-08-20 13:12 ` Yang Weijiang
2019-09-04 13:49 ` Yang Weijiang
2019-09-09 17:10 ` Paolo Bonzini
2019-09-11 0:23 ` Yang Weijiang
2019-08-14 7:04 ` [PATCH RESEND v4 9/9] KVM: MMU: Handle host memory remapping and reclaim Yang Weijiang
2019-08-14 12:36 ` [PATCH RESEND v4 0/9] Enable Sub-page Write Protection Support Paolo Bonzini
2019-08-14 14:02 ` Yang Weijiang
2019-08-14 14:06 ` Paolo Bonzini
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