From: Sean Christopherson <seanjc@google.com>
To: Michael Roth <michael.roth@amd.com>
Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev,
linux-mm@kvack.org, linux-crypto@vger.kernel.org,
x86@kernel.org, linux-kernel@vger.kernel.org,
tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de,
thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org,
pbonzini@redhat.com, vkuznets@redhat.com, jmattson@google.com,
luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com,
pgonda@google.com, peterz@infradead.org,
srinivas.pandruvada@linux.intel.com, rientjes@google.com,
dovmurik@linux.ibm.com, tobin@ibm.com, bp@alien8.de,
vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com,
tony.luck@intel.com, sathyanarayanan.kuppuswamy@linux.intel.com,
alpergun@google.com, jarkko@kernel.org, ashish.kalra@amd.com,
nikunj.dadhania@amd.com, pankaj.gupta@amd.com,
liam.merwick@oracle.com
Subject: Re: [PATCH v14 16/22] KVM: x86: Implement gmem hook for determining max NPT mapping level
Date: Wed, 24 Apr 2024 17:45:18 -0700 [thread overview]
Message-ID: <ZimnngU7hn7sKoSc@google.com> (raw)
In-Reply-To: <20240421180122.1650812-17-michael.roth@amd.com>
On Sun, Apr 21, 2024, Michael Roth wrote:
> ---
> arch/x86/kvm/svm/sev.c | 32 ++++++++++++++++++++++++++++++++
> arch/x86/kvm/svm/svm.c | 1 +
> arch/x86/kvm/svm/svm.h | 7 +++++++
> 3 files changed, 40 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index ff9b8c68ae56..243369e302f4 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -4528,3 +4528,35 @@ void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end)
> cond_resched();
> }
> }
> +
> +/*
> + * Re-check whether an #NPF for a private/gmem page can still be serviced, and
> + * adjust maximum mapping level if needed.
> + */
> +int sev_gmem_validate_fault(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, bool is_private,
This is a misleading name. The primary purpose is not to validate the fault, the
primary purpose is to get the max mapping level. The fact that this can fail
should not dictate the name.
I also think we should skip the call if the max level is already PG_LEVEL_4K.
Something _could_ race and invalidate the RMP, but that's _exactly_ why KVM
guards the page fault path with mmu_invalidate_seq.
Actually, is returning an error in this case even correct? Me thinks no. If
something invalidates the RMP between kvm_gmem_get_pfn() and getting the mapping
level, then KVM should retry, which mmu_invalidate_seq handles. Returning
-EINVAL and killing the VM is wrong.
And IMO, "gmem" shouldn't be in the name, this is not a hook from guest_memfd,
it's a hook for mapping private memory. And as someone called out somwhere else,
the "private" parameters is pointless. And for that matter, so is the gfn.
And even _if_ we want to return an error, we could even overload the return code
to handle this, e.g. in the caller:
r = static_call(kvm_x86_max_private_mapping_level)(vcpu->kvm, fault->pfn);
if (r < 0) {
kvm_release_pfn_clean(fault->pfn);
return r;
}
fault->max_level = min(fault->max_level, r);
but what I think we want is:
---
int sev_snp_private_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn)
{
int level, rc;
bool assigned;
if (!sev_snp_guest(kvm))
return 0;
rc = snp_lookup_rmpentry(pfn, &assigned, &level);
if (rc || !assigned)
return PG_LEVEL_4K;
return level;
}
static u8 kvm_max_private_mapping_level(struct kvm *kvm, kvm_pfn_t pfn,
u8 max_level, int gmem_order)
{
if (max_level == PG_LEVEL_4K)
return PG_LEVEL_4K;
max_level = min(kvm_max_level_for_order(gmem_order),max_level);
if (max_level == PG_LEVEL_4K)
return PG_LEVEL_4K;
return min(max_level,
static_call(kvm_x86_private_max_mapping_level)(kvm, pfn);
}
static int kvm_faultin_pfn_private(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
struct kvm *kvm = vcpu->kvm;
int max_order, r;
if (!kvm_slot_can_be_private(fault->slot)) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return -EFAULT;
}
r = kvm_gmem_get_pfn(kvm, fault->slot, fault->gfn, &fault->pfn, &max_order);
if (r) {
kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
return r;
}
fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY);
fault->max_level = kvm_max_private_mapping_level(kvm, fault->pfn,
fault->max_level, order);
return RET_PF_CONTINUE;
}
---
Side topic, the KVM_MEM_READONLY check is unnecessary, KVM doesn't allow RO memslots
to coincide with guest_memfd. I missed that in commit e563592224e0 ("KVM: Make
KVM_MEM_GUEST_MEMFD mutually exclusive with KVM_MEM_READONLY").
next prev parent reply other threads:[~2024-04-25 0:45 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-21 18:01 [PATCH v14 00/22] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Michael Roth
2024-04-21 18:01 ` [PATCH v14 01/22] KVM: SEV: Select KVM_GENERIC_PRIVATE_MEM when CONFIG_KVM_AMD_SEV=y Michael Roth
2024-04-21 18:01 ` [PATCH v14 02/22] KVM: SEV: Add support to handle AP reset MSR protocol Michael Roth
2024-04-21 18:01 ` [PATCH v14 03/22] KVM: SEV: Add GHCB handling for Hypervisor Feature Support requests Michael Roth
2024-04-24 20:21 ` Sean Christopherson
2024-04-25 20:52 ` Michael Roth
2024-04-25 21:55 ` Sean Christopherson
2024-04-21 18:01 ` [PATCH v14 04/22] KVM: SEV: Add initial SEV-SNP support Michael Roth
2024-04-21 18:01 ` [PATCH v14 05/22] KVM: SEV: Add KVM_SEV_SNP_LAUNCH_START command Michael Roth
2024-04-24 23:26 ` Sean Christopherson
2024-04-21 18:01 ` [PATCH v14 06/22] KVM: SEV: Add KVM_SEV_SNP_LAUNCH_UPDATE command Michael Roth
2024-04-24 23:58 ` Sean Christopherson
2024-04-21 18:01 ` [PATCH v14 07/22] KVM: SEV: Add KVM_SEV_SNP_LAUNCH_FINISH command Michael Roth
2024-04-21 18:01 ` [PATCH v14 08/22] KVM: SEV: Add support to handle GHCB GPA register VMGEXIT Michael Roth
2024-04-21 18:01 ` [PATCH v14 09/22] KVM: SEV: Add support to handle MSR based Page State Change VMGEXIT Michael Roth
2024-04-24 20:59 ` Sean Christopherson
2024-04-25 22:00 ` Michael Roth
2024-04-25 22:13 ` Sean Christopherson
2024-04-26 17:16 ` Michael Roth
2024-04-26 20:14 ` Sean Christopherson
2024-04-26 22:24 ` Michael Roth
2024-04-26 22:48 ` Michael Roth
2024-04-21 18:01 ` [PATCH v14 10/22] KVM: SEV: Add support to handle " Michael Roth
2024-04-21 18:01 ` [PATCH v14 11/22] KVM: SEV: Add support to handle RMP nested page faults Michael Roth
2024-04-21 18:01 ` [PATCH v14 12/22] KVM: SEV: Support SEV-SNP AP Creation NAE event Michael Roth
2024-04-21 18:01 ` [PATCH v14 13/22] KVM: SEV: Add support for GHCB-based termination requests Michael Roth
2024-04-21 18:01 ` [PATCH v14 14/22] KVM: SEV: Implement gmem hook for initializing private pages Michael Roth
2024-04-21 18:01 ` [PATCH v14 15/22] KVM: SEV: Implement gmem hook for invalidating " Michael Roth
2024-04-21 18:01 ` [PATCH v14 16/22] KVM: x86: Implement gmem hook for determining max NPT mapping level Michael Roth
2024-04-25 0:45 ` Sean Christopherson [this message]
2024-04-21 18:01 ` [PATCH v14 17/22] KVM: SEV: Avoid WBINVD for HVA-based MMU notifications for SNP Michael Roth
2024-04-25 0:17 ` Sean Christopherson
2024-04-21 18:01 ` [PATCH v14 18/22] KVM: SVM: Add module parameter to enable SEV-SNP Michael Roth
2024-04-21 18:01 ` [PATCH v14 19/22] KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event Michael Roth
2024-04-21 18:01 ` [PATCH v14 20/22] crypto: ccp: Add the SNP_VLEK_LOAD command Michael Roth
2024-04-21 18:01 ` [PATCH v14 21/22] crypto: ccp: Add the SNP_{PAUSE,RESUME}_ATTESTATION commands Michael Roth
2024-04-25 0:15 ` Sean Christopherson
2024-04-26 17:35 ` Michael Roth
2024-04-26 19:57 ` Sean Christopherson
2024-04-26 21:46 ` Michael Roth
2024-04-27 0:10 ` Sean Christopherson
2024-04-27 1:32 ` Michael Roth
2024-04-29 14:27 ` Sean Christopherson
2024-04-21 18:01 ` [PATCH v14 22/22] KVM: SEV: Provide support for SNP_EXTENDED_GUEST_REQUEST NAE event Michael Roth
2024-04-25 0:10 ` Sean Christopherson
2024-04-26 17:57 ` Michael Roth
2024-04-23 16:21 ` [PATCH v14 23/22] [SQUASH] KVM: SEV: Add support to handle GHCB GPA register VMGEXIT Michael Roth
2024-04-23 16:21 ` [PATCH v14 24/22] [SQUASH] KVM: SEV: Add support to handle MSR based Page State Change VMGEXIT Michael Roth
2024-04-23 16:21 ` [PATCH v14 25/22] [SQUASH] KVM: SEV: Add support to handle " Michael Roth
2024-04-23 16:21 ` [PATCH v14 26/22] [SQUASH] KVM: SEV: Add support for GHCB-based termination requests Michael Roth
2024-04-23 16:21 ` [PATCH v14 27/22] [SQUASH] KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event Michael Roth
2024-04-23 16:21 ` [PATCH v14 28/22] [SQUASH] KVM: SEV: Provide support for SNP_EXTENDED_GUEST_REQUEST " Michael Roth
2024-04-23 21:36 ` Jarkko Sakkinen
2024-04-23 16:21 ` [PATCH v14 29/22] [SQUASH] KVM: SEV: Support SEV-SNP AP Creation " Michael Roth
2024-04-23 16:31 ` [PATCH v14 00/22] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Michael Roth
2024-04-24 16:51 ` 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=ZimnngU7hn7sKoSc@google.com \
--to=seanjc@google.com \
--cc=ak@linux.intel.com \
--cc=alpergun@google.com \
--cc=ardb@kernel.org \
--cc=ashish.kalra@amd.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=dovmurik@linux.ibm.com \
--cc=hpa@zytor.com \
--cc=jarkko@kernel.org \
--cc=jmattson@google.com \
--cc=jroedel@suse.de \
--cc=kirill@shutemov.name \
--cc=kvm@vger.kernel.org \
--cc=liam.merwick@oracle.com \
--cc=linux-coco@lists.linux.dev \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=michael.roth@amd.com \
--cc=mingo@redhat.com \
--cc=nikunj.dadhania@amd.com \
--cc=pankaj.gupta@amd.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=pgonda@google.com \
--cc=rientjes@google.com \
--cc=sathyanarayanan.kuppuswamy@linux.intel.com \
--cc=slp@redhat.com \
--cc=srinivas.pandruvada@linux.intel.com \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=tobin@ibm.com \
--cc=tony.luck@intel.com \
--cc=vbabka@suse.cz \
--cc=vkuznets@redhat.com \
--cc=x86@kernel.org \
/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.