From: Paolo Bonzini <pbonzini@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>,
Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm <kvm@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Ben Gardon <bgardon@google.com>,
Brijesh Singh <brijesh.singh@amd.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH v2 07/17] KVM: x86/mmu: Check PDPTRs before allocating PAE roots
Date: Thu, 8 Apr 2021 14:09:09 +0200 [thread overview]
Message-ID: <f6ae3dbb-cfa5-4d8b-26bf-92db6fc9eab1@redhat.com> (raw)
In-Reply-To: <CANRm+CzUAzR+D3BtkYpe71sHf_nmtm_Qmh4neqc=US2ETauqyQ@mail.gmail.com>
On 08/04/21 13:15, Wanpeng Li wrote:
> I saw this splatting:
>
> BUG: sleeping function called from invalid context at
> arch/x86/kvm/kvm_cache_regs.h:115
> kvm_pdptr_read+0x20/0x60 [kvm]
> kvm_mmu_load+0x3bd/0x540 [kvm]
>
> There is a might_sleep() in kvm_pdptr_read(), however, the original
> commit didn't explain more. I can send a formal one if the below fix
> is acceptable.
I think we can just push make_mmu_pages_available down into
kvm_mmu_load's callees. This way it's not necessary to hold the lock
until after the PDPTR check:
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 0d92a269c5fa..f92c3695bfeb 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3244,6 +3244,12 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
u8 shadow_root_level = mmu->shadow_root_level;
hpa_t root;
unsigned i;
+ int r;
+
+ write_lock(&vcpu->kvm->mmu_lock);
+ r = make_mmu_pages_available(vcpu);
+ if (r < 0)
+ goto out_unlock;
if (is_tdp_mmu_enabled(vcpu->kvm)) {
root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu);
@@ -3266,13 +3272,16 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
mmu->root_hpa = __pa(mmu->pae_root);
} else {
WARN_ONCE(1, "Bad TDP root level = %d\n", shadow_root_level);
- return -EIO;
+ r = -EIO;
}
+out_unlock:
+ write_unlock(&vcpu->kvm->mmu_lock);
+
/* root_pgd is ignored for direct MMUs. */
mmu->root_pgd = 0;
- return 0;
+ return r;
}
static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
@@ -3282,6 +3291,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
gfn_t root_gfn, root_pgd;
hpa_t root;
int i;
+ int r;
root_pgd = mmu->get_guest_pgd(vcpu);
root_gfn = root_pgd >> PAGE_SHIFT;
@@ -3300,6 +3310,11 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
}
}
+ write_lock(&vcpu->kvm->mmu_lock);
+ r = make_mmu_pages_available(vcpu);
+ if (r < 0)
+ goto out_unlock;
+
/*
* Do we shadow a long mode page table? If so we need to
* write-protect the guests page table root.
@@ -3308,7 +3323,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
root = mmu_alloc_root(vcpu, root_gfn, 0,
mmu->shadow_root_level, false);
mmu->root_hpa = root;
- goto set_root_pgd;
+ goto out_unlock;
}
if (WARN_ON_ONCE(!mmu->pae_root))
@@ -3350,7 +3365,8 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
else
mmu->root_hpa = __pa(mmu->pae_root);
-set_root_pgd:
+out_unlock:
+ write_unlock(&vcpu->kvm->mmu_lock);
mmu->root_pgd = root_pgd;
return 0;
@@ -4852,14 +4868,10 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
r = mmu_alloc_special_roots(vcpu);
if (r)
goto out;
- write_lock(&vcpu->kvm->mmu_lock);
- if (make_mmu_pages_available(vcpu))
- r = -ENOSPC;
- else if (vcpu->arch.mmu->direct_map)
+ if (vcpu->arch.mmu->direct_map)
r = mmu_alloc_direct_roots(vcpu);
else
r = mmu_alloc_shadow_roots(vcpu);
- write_unlock(&vcpu->kvm->mmu_lock);
if (r)
goto out;
Paolo
next prev parent reply other threads:[~2021-04-08 12:09 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 1:10 [PATCH v2 00/17] KVM: x86/mmu: Lots of bug fixes Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 01/17] KVM: nSVM: Set the shadow root level to the TDP level for nested NPT Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 02/17] KVM: x86/mmu: Alloc page for PDPTEs when shadowing 32-bit NPT with 64-bit Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 03/17] KVM: x86/mmu: Capture 'mmu' in a local variable when allocating roots Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 04/17] KVM: x86/mmu: Allocate the lm_root before allocating PAE roots Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 05/17] KVM: x86/mmu: Allocate pae_root and lm_root pages in dedicated helper Sean Christopherson
2021-03-05 17:34 ` Paolo Bonzini
2021-03-05 1:10 ` [PATCH v2 06/17] KVM: x86/mmu: Ensure MMU pages are available when allocating roots Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 07/17] KVM: x86/mmu: Check PDPTRs before allocating PAE roots Sean Christopherson
2021-04-08 11:15 ` Wanpeng Li
2021-04-08 12:09 ` Paolo Bonzini [this message]
2021-04-08 15:48 ` Sean Christopherson
2021-04-08 15:57 ` Paolo Bonzini
2021-04-08 16:27 ` Sean Christopherson
2021-04-08 16:30 ` Paolo Bonzini
2021-03-05 1:10 ` [PATCH v2 08/17] KVM: x86/mmu: Fix and unconditionally enable WARNs to detect PAE leaks Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 09/17] KVM: x86/mmu: Use '0' as the one and only value for an invalid PAE root Sean Christopherson
2021-03-05 17:52 ` Paolo Bonzini
2021-03-05 18:22 ` Sean Christopherson
2021-03-05 18:23 ` Paolo Bonzini
2021-03-05 1:10 ` [PATCH v2 10/17] KVM: x86/mmu: Set the C-bit in the PDPTRs and LM pseudo-PDPTRs Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 11/17] KVM: x86/mmu: Mark the PAE roots as decrypted for shadow paging Sean Christopherson
2021-03-05 17:44 ` Paolo Bonzini
2021-03-05 18:02 ` Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 12/17] KVM: SVM: Don't strip the C-bit from CR2 on #PF interception Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 13/17] KVM: nVMX: Defer the MMU reload to the normal path on an EPTP switch Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 14/17] KVM: x86: Defer the MMU unload to the normal path on an global INVPCID Sean Christopherson
2021-03-05 1:10 ` [PATCH v2 15/17] KVM: x86/mmu: Unexport MMU load/unload functions Sean Christopherson
2021-03-05 1:11 ` [PATCH v2 16/17] KVM: x86/mmu: Sync roots after MMU load iff load as successful Sean Christopherson
2021-03-05 1:11 ` [PATCH v2 17/17] KVM: x86/mmu: WARN on NULL pae_root or lm_root, or bad shadow root level Sean Christopherson
2021-03-05 17:53 ` [PATCH v2 00/17] KVM: x86/mmu: Lots of bug fixes Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f6ae3dbb-cfa5-4d8b-26bf-92db6fc9eab1@redhat.com \
--to=pbonzini@redhat.com \
--cc=bgardon@google.com \
--cc=brijesh.singh@amd.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kernellwp@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=seanjc@google.com \
--cc=thomas.lendacky@amd.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.