From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Borislav Petkov <bp@suse.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
Brijesh Singh <brijesh.singh@amd.com>
Subject: Re: [PATCH v5 15/15] KVM: SVM: Skip SEV cache flush if no ASIDs have been used
Date: Thu, 22 Apr 2021 09:30:02 +0200 [thread overview]
Message-ID: <a7e15de5-5b04-7a33-1d7d-81edf07193ba@redhat.com> (raw)
In-Reply-To: <20210422021125.3417167-16-seanjc@google.com>
On 22/04/21 04:11, Sean Christopherson wrote:
> + int ret, pos, error = 0;
> +
> + /* Check if there are any ASIDs to reclaim before performing a flush */
> + pos = find_next_bit(sev_reclaim_asid_bitmap, max_sev_asid, min_asid);
> + if (pos >= max_asid)
> + return -EBUSY;
There's a tiny bug here which would cause sev_flush_asids to return 0
if there are reclaimed SEV ASIDs and the caller is looking for an SEV-ES
ASID, or vice versa. The bug used to be in __sev_recycle_asids, you're
just moving the code.
It's not a big deal because sev_asid_new only retries once, but we might
as well fix it:
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 02b3426a9e39..403c6991e67c 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -74,12 +74,13 @@ struct enc_region {
unsigned long size;
};
+/* Called with the sev_bitmap_lock held, or on shutdown */
static int sev_flush_asids(int min_asid, int max_asid)
{
int ret, pos, error = 0;
/* Check if there are any ASIDs to reclaim before performing a flush */
- pos = find_next_bit(sev_reclaim_asid_bitmap, max_sev_asid, min_asid);
+ pos = find_next_bit(sev_reclaim_asid_bitmap, max_asid, min_asid);
if (pos >= max_asid)
return -EBUSY;
Paolo
> /*
> * DEACTIVATE will clear the WBINVD indicator causing DF_FLUSH to fail,
> @@ -87,14 +92,7 @@ static inline bool is_mirroring_enc_context(struct kvm *kvm)
> /* Must be called with the sev_bitmap_lock held */
> static bool __sev_recycle_asids(int min_asid, int max_asid)
> {
> - int pos;
> -
> - /* Check if there are any ASIDs to reclaim before performing a flush */
> - pos = find_next_bit(sev_reclaim_asid_bitmap, max_sev_asid, min_asid);
> - if (pos >= max_asid)
> - return false;
> -
> - if (sev_flush_asids())
> + if (sev_flush_asids(min_asid, max_asid))
> return false;
>
> /* The flush process will flush all reclaimable SEV and SEV-ES ASIDs */
> @@ -1846,10 +1844,11 @@ void sev_hardware_teardown(void)
> if (!sev_enabled)
> return;
>
> + /* No need to take sev_bitmap_lock, all VMs have been destroyed. */
> + sev_flush_asids(0, max_sev_asid);
> +
> bitmap_free(sev_asid_bitmap);
> bitmap_free(sev_reclaim_asid_bitmap);
> -
> - sev_flush_asids();
> }
>
> int sev_cpu_init(struct svm_cpu_data *sd)
>
next prev parent reply other threads:[~2021-04-22 7:31 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 2:11 [PATCH v5 00/15] KVM: SVM: Misc SEV cleanups Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 01/15] KVM: SVM: Zero out the VMCB array used to track SEV ASID association Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 02/15] KVM: SVM: Free sev_asid_bitmap during init if SEV setup fails Sean Christopherson
2021-04-22 19:34 ` Tom Lendacky
2021-04-22 2:11 ` [PATCH v5 03/15] KVM: SVM: Disable SEV/SEV-ES if NPT is disabled Sean Christopherson
2021-04-22 7:14 ` Paolo Bonzini
2021-04-22 16:15 ` Sean Christopherson
2021-04-22 17:08 ` Paolo Bonzini
2021-04-22 18:11 ` Sean Christopherson
2021-04-23 7:08 ` Paolo Bonzini
2021-04-22 2:11 ` [PATCH v5 04/15] KVM: SVM: Move SEV module params/variables to sev.c Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 05/15] KVM: SEV: Mask CPUID[0x8000001F].eax according to supported features Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 06/15] x86/sev: Drop redundant and potentially misleading 'sev_enabled' Sean Christopherson
2021-04-22 12:05 ` Paolo Bonzini
2021-04-22 12:18 ` Borislav Petkov
2021-04-22 12:16 ` Borislav Petkov
2021-04-22 2:11 ` [PATCH v5 07/15] KVM: SVM: Append "_enabled" to module-scoped SEV/SEV-ES control variables Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 08/15] KVM: SVM: Condition sev_enabled and sev_es_enabled on CONFIG_KVM_AMD_SEV=y Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 09/15] KVM: SVM: Enable SEV/SEV-ES functionality by default (when supported) Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 10/15] KVM: SVM: Unconditionally invoke sev_hardware_teardown() Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 11/15] KVM: SVM: Explicitly check max SEV ASID during sev_hardware_setup() Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 12/15] KVM: SVM: Move SEV VMCB tracking allocation to sev.c Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 13/15] KVM: SVM: Drop redundant svm_sev_enabled() helper Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 14/15] KVM: SVM: Remove an unnecessary prototype declaration of sev_flush_asids() Sean Christopherson
2021-04-22 2:11 ` [PATCH v5 15/15] KVM: SVM: Skip SEV cache flush if no ASIDs have been used Sean Christopherson
2021-04-22 7:30 ` Paolo Bonzini [this message]
2021-04-22 7:30 ` [PATCH v5 00/15] KVM: SVM: Misc SEV cleanups Paolo Bonzini
2021-04-22 16:02 ` Sean Christopherson
2021-04-22 17:08 ` Paolo Bonzini
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